- Email: [email protected]
Influence of high-flux hemodialysis and hemodiafiltration on serum C-terminal agrin fragment levels in end-stage renal disease patients
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
ORIGINAL ARTICLE Q1
Q14
Influence of high-flux hemodialysis and hemodiafiltration on serum C-terminal agrin fragment levels in end-stage renal disease patients DOMINIK STEUBL, STEFAN HETTWER, PIUS DAHINDEN, PETRA WOLF, PETER LUPPA, € CARSTEN A. WAGNER, CLAUDIUS KUCHLE, CHRISTOPH SCHMADERER, LUTZ RENDERS, UWE HEEMANN, and MARCEL ROOS € MUNCHEN, GERMANY AND ZURICH, SWITZERLAND
Q3
Q4
C-terminal agrin fragment (CAF, 22 kDa) has been shown to be a promising new rapid biomarker for kidney function. This study evaluated the influence of hemodialysis (HD) and hemodiafiltration (HDF) treatment on serum CAF concentrations in patients with end-stage renal disease (ESRD). A total of 36 patients with ESRD undergoing chronic HD/HDF treatment were enrolled (21 high-flux-HD/Fx60 membrane, 7 highflux-HD/Elisio19H membrane, and 8 HDF/Elisio19H membrane). On a midweek session, blood samples were obtained before, at halftime, and post-treatment. Dialysate samples were obtained 4 times during treatment. Serum and dialysate CAF, cystatin C, urea, and creatinine concentrations were measured. Reduction ratios (RRs), total solute removal, overall dialytic clearance, and instantaneous dialytic clearance at halftime were calculated and compared. Although HD/Elisio19H and HDF/ Elisio19H treatments significantly reduced CAF concentrations (RR 46.6 6 9.1% and 57.6 6 11.7%, respectively, P 5 0.018 and P 5 0.001), HD/Fx60 treatment did not remove CAF from serum (RR 2.4 6 15.4%, P 5 0.25), there was no relevant CAF detection in dialysate. In the HD/Fx60 group, the RR of CAF was significantly lower compared with cystatin C, urea, and creatinine, in which significant removal was detected (37.9 6 14.8%, 65.0 6 10.7%, and 56.0 6 9.8%, respectively, P , 0.001). CAF is a new biomarker for kidney function whose serum concentration is not influenced by conventional high-flux HD using Fx60 membrane. It might therefore represent a promising dialysis-independent biomarker for evaluation of kidney function, for example, in acute kidney failure. (Translational Research 2014;-:1–8) Abbreviations: AKI ¼ acute kidney injury; BW ¼ body weight; CAF ¼ C-terminal agrin fragment; ECV ¼ extracellular volume; ESRD ¼ end-stage renal disease; HD ¼ hemodialysis; HDF ¼ hemodiafiltration; IDC ¼ instantaneous dialytic clearance; LMWP ¼ low-molecular-weight protein; ODC ¼ overall dialytic clearance; RR ¼ reduction ratio; TSR ¼ total solute removal; UF ¼ ultrafiltration
From the Abteilung f€ur Nephrologie, Klinikum rechts der Isar, M€ unchen, Germany; Neurotune AG, Schlieren-Zurich, Switzerland; Institut f€ ur Medizinische Statistik und Epidemiologie, Klinikum rechts der Isar, M€ unchen, Germany; Institut f€ur Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, M€unchen, Germany; Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
Reprint requests: Dominik Steubl, Department of Nephrology, Klinikum rechts der Isar, Ismaninger Street 22 D-81675 M€unchen, Germany; e-mail: [email protected]. 1931-5244/$ - see front matter Ó 2014 Mosby, Inc. All rights reserved. http://dx.doi.org/10.1016/j.trsl.2014.05.005
Submitted for publication March 6, 2014; revision submitted May 8, 2014; accepted for publication May 10, 2014.
1 FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104
2
105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158
Translational Research - 2014
Steubl et al
AT A GLANCE COMMENTARY Steubl D, et al. Background
The evaluation of residual renal function in patients undergoing extracorporeal treatment is difficult to assess because conventional biomarkers are eliminated by dialysis. We evaluated C-terminal agrin fragment (CAF), which was shown to be a new biomarker for kidney function in another study, in hemodialysis treatment. We showed that CAF is not eliminated by conventional highflux hemodialysis. Translational Significance
CAF, originally characterized in basic neuroscience, is a new dialysis-independent biomarker for kidney function and might therefore be of additive value in the field of clinical nephrology.
INTRODUCTION
Q5
Acute kidney failure (AKI) and chronic kidney disease are important problems in various clinical settings, leading to the accumulation of uremic toxins, electrolyte disturbances, fluid overload and changes in acid-base homeostasis.1 Often extracorporeal treatment such as hemodialysis (HD) and hemofiltration is required acutely or as chronic renal replacement therapy.2,3 Once extracorporeal treatment has been initiated, the judgment if and to what extent renal function regenerates or further decreases is impeded by the fact that the routinely used serum biomarkers of renal function, such as serum creatinine, urea, or cystatin C, are eliminated by extracorporeal treatment.4-6 Therefore, clinicians must rely on inaccurate markers such as urinary output. A definitive decision on the current situation of renal function requires discontinuation of extracorporeal treatment followed by monitoring of serum creatinine, urea, and cystatin C concentrations. This approach generates additional costs, consumes time, and might put the patient at risk. Therefore, a serum marker that monitors kidney function unaffected by extracorporeal treatment would be desirable. Recently, we characterized serum C-terminal agrin fragment (CAF), a 22 kDa protein derived from agrin, as a new biomarker for kidney function.7 It correlates with serum creatinine concentrations (logarithmic correlation r 5 0.74) and eGFR (logarithmic correlation r 5 20.77), and reacts more rapidly to changes in renal function than creatinine. Because of CAF’s molecular
weight of 22 kDa, we hypothesized that serum CAF concentrations might not be significantly influenced by extracorporeal treatment using high-flux dialyzers, preliminary data confirmed this assumption. The present study evaluated the time course of serum CAF concentrations under different treatment modalities (HD and hemodiafiltration [HDF]) in chronic HD patients using 2 different high-flux membranes and compared it with 3 markers of kidney function: creatinine, urea, and cystatin C. The aim of the survey was not to evaluate CAF as a biomarker for kidney function. This was already proven in the former study.7 Instead the aim was uniquely to assess the influence of different extracorporeal treatments on serum CAF concentrations. We chose a group of patients with a daily urinary output of less that 500 mL because we assumed that the average urine production during a 5-hour HD session should not exceed a maximum of 100 mL, and we know from another study (unpublished data) that the Q6 renal clearance of CAF in patients with a daily urinary output of 100 mL is negligible. Thereby, we wanted to minimize the confounding factor of relevant endogenous renal clearance of CAF during HD treatment that might influence the difference between pre- and postserum CAF levels. Changes should only rely on clearance via the HD treatment. MATERIALS AND METHODS Study design and patients. The study was approved by the local Ethics Approval Committee (Klinikum rechts der Isar, Technische Universit€at, Munich, Germany) and is in line with the declaration of Helsinki. All patients enrolled in this study gave their informed consent. The study was performed with a cross-sectional, noncrossover, nonrandomized, open-label proof-ofprinciple design. The group is a representative sample of the chronic dialysis collective at our center. The groups were not matched for certain parameters; patients were not assigned to a treatment group intentionally. The reason why patients received a certain treatment was based on medical reasons such as insufficient kt/V levels or membrane intolerance. No specific inclusion or exclusion criteria had to be met. A total of 36 stable, adult oliguric/anuric HD patients Q7 (23 males, 13 females, mean age 62.6 6 16.6 years) who had been on chronic thrice-weekly maintenance HD/HDF treatment for at least 3 months without acute illness were enrolled. The primary underlying diseases were diabetic nephropathy (n 5 4), renal vascular disease (n 5 5), immunologic disorders (n 5 8), autosomal-dominant polycystic kidney disease (n 5 2), cardiorenal syndrome (n 5 2), and others (including unknown cases, n 5 15).
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212
Translational Research Volume -, Number -
213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266
Steubl et al
In all patients serum and dialysate samples were taken at a midweek session. Primary outcome parameter was the removal of CAF, creatinine, urea, and cystatin C from serum in the form of reduction ratio (RR). Secondary outcomes included intradialytic changes in serum and dialysate concentrations, total solute removal (TSR), instantaneous dialytic clearance (IDC) at halftime, and in case of CAF and cystatin C, overall dialytic clearance (ODC). Treatment and technique characteristics. All patients received treatment with either a Fresenius 4008H or 5008H machine (Fresenius Medical Care, Bad Homburg, Germany; Table I) in a 2-needle mode. Vascular access was arteriovenous fistula in 30 patients (native in 26, synthetic graft in 4) and central venous catheter in 6 patients. All patients had a sufficient HD dose, indicated by a kt/V . 1.2 in a previous measurement. Twenty-eight patients received high-efficiency, highflux, and high-permeability HD. In 21 of these patients an Fx60 membrane (high-flux polysulfone membrane; Fresenius Medical Care) was used (group named HD/ Fx60), 7 (group named HD/E19H) received treatment using an Elisio19H membrane (high-flux Polynephron membrane; Nipro Europe N.V., Zaventem, Belgium). Treatment duration ranged between 3.5 and 5 hours, and the effective blood flow between 200 and 300 mL/ min. The dialysate flow was set to 500 mL/min in every patient. Eight patients received postdilution HDF treatment using an Elisio19H dialyzer (group named HDF/E19H). Treatment ranged from 4.5 to 5 hours, and blood flow from 250 to 280 mL/min. The dialysate flow was 500 mL/min in every patient. A description of patients’ demographics and treatments can be found in Table II. Membrane characteristics are listed in Table IV (Supplementary material). Sample collection and laboratory analysis. Blood samples were obtained before initiation of treatment, at halftime, and after cessation of treatment. Pre- (cserum-pre) and post-treatment (cserum-post) samples were obtained directly from the vascular access. The post-treatment sample was collected 2 minutes after the blood pump had been set to 50 mL/min followed by a stop of the pump.8 The half-time sample (cserum-1/2) was collected directly from the arterial tubing. Dialysate was collected directly from the effluent tubing 1 minute after the initiation of treatment (cdial-pre), after 1 hour (cdial-1h), at halftime (cdial-1/2), and 1 minute before the cessation of treatment (cdial-post). Blood samples were centrifuged at 3000 rpm for 8 minutes, then the serum was collected and both serum and dialysate stored at 280 C until analysis was performed. Analysis included measurement of CAF, creatinine, urea, and cystatin C concentrations. CAF concentrations were measured using a commercially available
3
Table I. Patient’s and treatment characteristics Parameter
HD/Fx60
HD/Elisio19H
HDF/Elisio19H
Gender 14/7 4/3 6/2 (male/female) Age (y) 62.1 6 17.7 67.6 6 18.1 59.6 6 9.7 Machine (Fresenius 12/9 0/7 1/7 4008/5008) Anticoagulation 14/7 7/0* 8/0* (Hep./citrate) BWpre (kg) 69.0 6 14.7 75.5 6 14.4 82.9 6 17.1 68.5 6 14.7 74.0 6 14.0 80.5 6 17.0 BWpost (kg) UFV (L) 1.0 6 0.9 1.9 6 1.0* 3.0 6 0.7* t (h) 4.0 6 0.4 4.1 6 0.6 4.9 6 0.2*† QB (mL/min) 240 6 34 253 6 22 261 6 11 Substitution — — 65.3 6 2.8 volume (mL/min) CBF (L) 55.2 6 12.1 61.7 6 8.0 73.7 6 3.2 QD (mL/min) 500 6 0 500 6 0 500 6 0 CDF (L) 117.0 6 18.0 125.0 6 17.3 146.3 6 6.5 Abbreviations: BWpre, body weight before treatment; BWpost, body weight after treatment; CBF, cumulative blood flow; CDF, cumulative dialysate flow; Hep, heparin; QB, blood flow; QD, dialysate flow; t, treatment duration; UFV, ultrafiltration volume. *P , 0.05 vs HD/Fx60. † P , 0.05 vs HD/Elisio19H.
enzyme-linked immunosorbent assay kit (NTCAF Elisa Kit; Neurotune, Schlieren, Switzerland) as described previously.7,9 Creatinine and urea were quantified by photometric techniques (creatinine, normal range 0.7–1.3 mg/dL in males and 0.5–1.1 mg/dL in females; urea, normal range 7–18 mg/dL). Cystatin C concentrations were determined using a nephelometric, latex-enhanced assay kit from Siemens Healthcare Diagnostics (Eschborn, Germany). The measurements were performed on an automated BN Prospec nephelometer from Siemens.10 Calculations. For the low-molecular-weight proteins (LMWPs), CAF and cystatin C cserum-1/2 and cserum-post were corrected for extracellular volume (ECV) changes.11 cserum-post was corrected for the difference in the patient’s pretreatment body weight (BWpre) and post-treatment body weight (BWpost) according to the formula11 cserumpost=corr 5 cserumpost 11 BWpre 2BWpost 0:2 3 BWpost : For cserum-1/2 we assumed that the BW, although not measured, would be half of the difference between BWpre and BWpost leading to the following formula: cserum1=2=corr 5 cserum1=2 11 BWpre 2 BWpost 2 1 BWpost 0:2 3 BWpost : 2 1 BWpost
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320
4
321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374
Translational Research - 2014
Steubl et al
Table II. Serum levels and RRs Parameter
Creatinine (mg/dL) HD/Fx60 HD/Elisio19H HDF/Elisio19H Urea (mg/dL) HD/Fx60 HD/Elisio19H HDF/Elisio19H Cystatin C (mg/L) HD/Fx60 HD/Elisio19H HDF/Elisio19H CAF (pmol) HD/Fx60 HD/Elisio19H HDF/Elisio19H
cserum-pre
cserum-½
cserum-post
RRpre-1/2 (%)
RRpre-post (%)
5.3 6 1.9 6.5 6 1.3 9.4 6 1.3†
2.9 6 0.9 3.1 6 0.6 4.4 6 0.8
2.1 6 0.7 2.0 6 0.5 3.1 6 0.8
40.9 6 10.4 49.4 6 6.7 48.9 6 4.9
56.0 6 9.8* 65.1 6 6.5* 60.3 6 7.7
39.6 6 15.5 54.3 6 14.2 45.3 6 13.7
19.4 6 7.5 22.7 6 6.2 18.6 6 5.9
11.8 6 4.2 12.5 6 4.0 11.6 6 4.4
46.4 6 11.6 55.3 6 6.7 55.4 6 3.7
65.0 6 10.7‡ 74.1 6 5.5‡ 70.7 6 5.6
4.1 6 1.3 4.6 6 0.8 4.4 6 1.1
2.8 6 0.9 2.3 6 0.5 2.2 6 0.6
2.5 6 0.7 1.7 6 0.2 1.4 6 0.5
30.8 6 13.3 49.7 6 12.7 50.4 6 8.5
37.9 6 14.8§ 61.1 6 10.1 69.3 6 6.9
1508.7 6 709.3 1167.2 6 574.9 598.9 6 354.9
4.0 6 13.3 35.6 6 13.5 46.1 6 11.1
2.4 6 15.4§ 46.6 6 9.1i 57.6 6 11.7i
1527.8 6 904.5 2196.0 6 1023.1 1467.8 6 946.9
1522.70 6 705.3 1380.4 6 674.9 771.3 6 439.3
Abbreviations: CAF, C-terminal agrin fragment; cserum-pre, serum concentration before treatment; cserum-½, serum concentration at halftime of treatment; cserum-post, serum concentration at the end of treatment; HD, hemodialysis; HDF, hemodiafiltration; RRpre-1/2, reduction ratio at halftime of treatment to before treatment; RRpre-post, reduction ratio at the end of treatment to before treatment. *P 5 0.013. † P , 0.05 vs cserum-pre HD/Fx60/HD/Elisio19H. ‡ P 5 0.026. § P , 0.001 vs HD/Elisio19H/HDF/Elisio19H. i P 5 0.04.
The RR from pretreatment to half-time treatment (RRpre-1/2) and from pretreatment to post-treatment (RRpre-post) for CAF and cystatin C were calculated according to the formula6 RR ð%Þ5 cserumpre 2cserumpost=corr cserumpre 3 100: Analogous to the RR for creatinine and urea were calculated according to the formula: RR ð%Þ5 cserumpre 2 cserumpost cserumpre 3 100: To assess an IDC of all substances at halftime of treatment, dialytic-sided clearance was calculated according to the following formula12: IDCðmL=minÞ5 cdial1=2 3 QD cserum1=2 ; where QD is the dialysate flow in milliliter per minute. Similar to b2-microglobulin, we used the single compartment model of Leypoldt et al. for calculation of an overall extracorporeal clearance of CAF and cystatin C13,14: ODC 5 QUF 3 12ln cserumpost cserumpre ln 3 1 1 UF ECVpost : In this formula, QUF represents the hourly ultrafiltration rate derived from the difference of pre- and posttreatment body weight. UF represents the total ultrafil-
tration volume, calculated from QUF and the treatment time. Postdialytic extracellular fluid (ECVpost) was Q8 assumed to be one-third of total body water.14 The total body water was calculated according to the anthropometric measurements reflecting age, height, and weight of the patient.15 The solute concentration time curves in serum and dialysate were used to calculate the area under the curve using the trapezoidal method. These data were multiplied by the accumulated volume and the corresponding amount of time to obtain the TSR. Statistical analysis. For statistical analysis IBM SPSS 20 and R 2.15.1 (R Foundation for Statistical Computing, Vienna, Austria) were used. The KolmogorovSmirnov test was performed to evaluate the normality of data distribution. Continuous data are expressed as the mean with standard deviation (SD), and categorical variables are reported in absolute numbers and percentages. Categorical baseline variables between the groups were compared using chi-square test. For comparison of RR, IDC, and ODC of CAF, cystatin C, urea, and creatinine within 1 extracorporeal treatment method/1 patient the Wilcoxon-Rank test was used. Q9 To compare continuous variables between the groups as well as RR, IDC, and ODC of 1 biomarker between the groups, the Mann-Whitney U test was performed. All analyses were done using a 2-sided 0.05 level of significance and have not been adjusted for multiple testing.
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428
Translational Research Volume -, Number -
429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482
Steubl et al
5
Fig 1. (A) RRs of different biomarkers compared within 1 extracorporeal procedure. Values are presented as the mean and standard deviation. (B) RRs of different biomarkers compared between 3 different extracorporeal procedures. Values are presented as the mean and standard deviation. CAF, C-terminal agrin fragment; CyC, cystatin C; Crea, creatinine; Fx60 HD, hemodialysis treatment performed with Fx60 membrane; Elisio HD, hemodialysis treatment performed with Elisio19H membrane; Elisio HDF, hemodiafiltration treatment performed with Elisio19H membrane; RR, reduction ratio.
RESULTS Baseline characteristics of the treatment groups.
According to the patients’ personal and treatment parameters in the group HD/Fx60, the total ultrafiltration volume was significantly lower than in HD/E19H and HDF/E19H (P , 0.05; Table I). Compared with HDF/E19H, the treatment time was significantly shorter in HD/Fx60 and HD/E19H (P , 0.05; Table I). In HD/Fx60 significantly more patients received citrate anticoagulation compared with HD/E19H and HDF/E19H (Table I). Apart from this, the groups were comparable without any further statistically significant differences. Clearance
of
small
water-soluble
substances.
Pretreatment serum creatinine concentrations were comparable between HD/Fx60 and HD/E19H but were significantly higher in HDF/E19H (P , 0.05; Table II). In all treatment groups, serum creatinine concentrations decreased significantly by 56.0%, 65.1%, and 60.3%, respectively (HD/Fx60 [P , 0.001], HD/E19H [P 5 0.018], HDF/E19H [P 5 0.012]; Table II, Fig 1, B). The reduction was only significantly greater in HD/ E19H compared with HD/Fx60 (P 5 0.013). Pretreatment urea concentrations were not significantly different between the groups. In all groups, there
was a significant reduction in urea concentrations of 65.0%, 74.1%, and 70.7%, respectively (HD/Fx60 [P , 0.001], HD/E19H [P 5 0.018], HDF/E19H [P 5 0.001]; Table II, Fig 1, B). The reduction was significantly greater only in HD/E19H compared with HD/Fx60 (P 5 0.026). Clearance of LMWPs. Pretreatment cystatin C concentrations were not significantly different between the groups. A significant reduction could be detected in all groups, resulting in RR of 37.9% (P , 0.001) in HD/ Fx60, 61.1% (P 5 0.001) in HD/E19H, and 69.3% in HDF/E19H (P 5 0.012; Table II, Fig 1, B). RR in HD/ E19H and HDF/E19H was significantly greater than in HD/Fx60 (P , 0.001 in both cases; Table II, Fig 1, B), whereas it did not differ significantly between HD/ E19H and HDF/E19H (P 5 0.094; Table II, Fig 1, B). Pretreatment CAF concentrations did not differ significantly between the 3 groups. A significant reduction was reached in HD/E19H and HDF/E19H (46.6% and 57.6%, P 5 0.018 and P 5 0.001, respectively; Table II, Fig 1, B), whereas in HD/Fx60 no significant reduction in CAF serum concentrations was seen (2.4%, P 5 0.25; Table II, Fig 1, B). Consequently, the RR was significantly lower in HD/Fx60 compared with HD/E19H and HDF/E19H (P , 0.001 in both
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536
6
537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590
Translational Research - 2014
Steubl et al
Table III. Dialysate levels, total solute removal, and dialytic clearances Parameter
Q2
Creatinine (mg/dL) Fx60-HD (G1) Elisio19H-HD (G2) (G3) Urea (mg/dL) Fx60-HD (G1) Elisio19H-HD (G2) Elisio19H-HDF (G3) CAF (pmol) Fx60-HD (G1) Elisio19H-HD (G2) Elisio19H-HDF (G3) Cystatin C (mg/L) Fx60-HD (G1) Elisio19H-HD (G2) Elisio19H-HDF (G3)
t50
t51h
t5½
t51
1.1 6 0.6 1.7 6 0.5 1.8 6 0.4
1.0 6 0.5 1.3 6 0.3 1.8 6 0.3
0.8 6 0.3 0.9 6 0.2 1.2 6 0.3
0.5 6 0.3 0.6 6 0.2 0.9 6 0.3
10.3 6 4.6 15.7 6 1.0 11.0 6 3.8
9.0 6 4.5 13.0 6 3.0 10.1 6 3.3
7.8 6 5.3 8.3 6 2.6 6.7 6 2.6
13.8 6 13.3 40.4 6 17.0 88.0 6 33.2
7.1 6 8.4 26.9 6 23.3 51.5 6 20.6
0.17 6 0.07 0.38 6 0.14 0.42 6 0.17
0.14 6 0.06 0.29 6 0.04 0.40 6 0.08
TSR (mg)
ODC (mL/min)
IDC (mL/min)
709.6 6 349.7 959.4 6 337.2 1715.4 6 342.1
— — —
130.1 6 32.1 137.9 6 25.6 121.3 6 18.5
4.3 6 3.6 4.7 6 1.9 5.0 6 1.7
3938.3 6 2363.8 5643.7 6 2392.6 6627.7 6 2092.8
— — —
167.0 6 40.1 173.9 6 42.2 164.0 6 28.3
6.1 6 7.0 24.7 6 20.2 36.5 6 8.8
7.5 6 9.3 16.1 6 9.9 28.4 6 8.3
0.01 6 0.01 0.05 6 0.05 0.11 6 0.03
2.1 6 8.0 34.9 6 9.9 49.5 6 21.3
3.6 6 4.6 17.6 6 3.1 28.8 6 15.0
0.10 6 0.04 0.18 6 0.07 0.24 6 0.08
0.09 6 0.03 0.14 6 0.06 0.16 6 0.08
9.90 6 4.72 21.20 6 8.26 35.88 6 8.48
21.2 6 16.6 52.1 6 12.4 64.9 6 17.0
18.2 6 5.7 39.2 6 16.8 50.0 6 10.9
Abbreviations: CAF, C-terminal agrin fragment; HD, hemodialysis; HDF, hemodiafiltration; IDC, instantaneous dialytic-sided clearance at 1 hour of treatment; ODC, overall dialytic clearance; TSR, total solute removal; t 5 0, before treatment; t 5 1 h, after 1 hour of treatment; t 5 ½, at halftime of treatment; t 5 1, at the end of treatment.
cases; Table II, Fig 1, B). RR of CAF was significantly higher in HDF/E19H compared with HD/E19H (P 5 0.04; Table II, Fig 1, B). Comparison of RRs of CAF and the other biomarkers within the 3 treatment modalities. When we compared
the RR of CAF with the other biomarkers within the 3 treatment modalities, the RR of CAF in HD/Fx60 was significantly lower compared with cystatin C, creatinine, and urea (2.4% vs 37.9%, 56.0%, and 65.0%, respectively, P , 0.001 in all cases; Table II, Fig 1, A). In HD/E19H, the RR of CAF was significantly lower compared with creatinine and urea (46.6% vs. 65.1% and 74.1% respectively, P 5 0.018; Table II, Fig 1, A), but not to cystatin C (46.6% vs 61.1%, P 5 0.063; Table II, Fig 1, A). In HDF/E19H, the RR of CAF was significantly lower than of cystatin C and urea (57.6% vs 69.3% and 70.7%, respectively, P 5 0.05 and P 5 0.025; Table II, Fig 1, A), whereas there was no significant difference between CAF and creatinine (57.6% vs 60.3%; P 5 0.58, Table II, Fig 1, A). TSR of CAF in the 3 treatment modalities. CAF was most effectively removed by HDF/E19H (0.11 mg) compared with HD/Fx60 (0.01 mg, P , 0.001) and HD/E19H (0.05 mg, P 5 0.021). HD/E19H was significantly more effective than HD/Fx60 (P 5 0.003; Table III). The TSR of the other 3 biomarkers can be found in Table III. ODC of CAF. The ODC of CAF was highest in the HDF group (49.5 mL/min) compared with HD/Fx60 (2.1 mL/min, P , 0.001) and HD/E19H (34.9 mL/ min, P 5 0.152). ODC of CAF was significantly higher in HD/E19H compared with HD/Fx60 (P , 0.001).
Comparing CAF and cystatin C, the ODC of cystatin C was significantly higher than the ODC of CAF in HD/ Fx60 and HDF/E19H (21.2 vs 2.1 mL/min, P 5 0.001 and 64.9 vs 49.5 mL/min, P 5 0.05 respectively; Table III), whereas it was not significantly different in HD/E19H (52.1 vs 34.9 mL/min, P 5 0.063, Table III). Instantaneous dialytic-sided clearance at halftime of treatment. IDC of CAF was significantly higher
in HDF/E19H compared with both HD/Fx60 (28.8 vs 3.6 mL/min, P , 0.001) and HD/E19H (17.6 mL/min, P 5 0.005). IDC of HD/E19H was significantly higher compared with HD/Fx60 (P 5 0.042; Table III). The IDCs of the other 3 biomarkers in the different treatment procedures can be found in Table III. DISCUSSION
This is the first study to evaluate the influence of extracorporeal treatment on CAF serum concentrations and to compare it with other serum biomarkers of kidney function, urea, creatinine, and cystatin C. Therefore, the aim of the study was not to assess CAF as a biomarker for kidney function in this group of patients but only focus on extracorporeal elimination. We evaluated HD treatment using 2 different membranes, Fx60 and Elisio19H, and HDF treatment using an Elisio19H membrane. We could demonstrate that, in contrast to cystatin C, urea, and creatinine, serum CAF concentrations are not significantly influenced by high-flux HD treatment using an Fx60 membrane. Besides this major finding, we also detected that the Elisio 19H is highly efficient in removing LMWPs up to the size of 22 kDa in regular HD treatment, although HD was inferior to HDF using
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644
Translational Research Volume -, Number -
645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698
Q10
Q11
Steubl et al
the same membrane concerning CAF removal, whereas HD treatment was superior to HDF treatment concerning creatinine and urea removal. Because instantaneous dialytic-sided clearance allowed us to detect a substantial amount of CAF in the dialytic fluid, we demonstrated that the reduction in CAF serum concentrations was mainly because of real removal instead of adsorption to the membrane surface. Our results show that high-flux HD using Fx60 was unable to remove CAF from patient’s blood, as demonstrated by different parameters such as RR, IDC, ODC, and TSR. CAF might therefore represent a promising biomarker to monitor residual renal function unaffected from intermittent high-flux HD with Fx60 membrane, although the topic ‘‘CAF as a biomarker for residual renal function’’ was not tested in this study but is already shown earlier.7 Furthermore, we could show that urea, creatinine, and cystatin C were substantially removed by intermittent high-flux HD using both Fx60 and Elisio19H membranes. Although cystatin C has been advocated to be useful for monitoring residual kidney function in critically ill patients receiving hemofiltration and HDF,16,17 in both studies as well as another study investigating hemofiltration and HDF18 a relevant elimination of cystatin C was detected. So it has to be questioned if this assumption really holds true for larger populations. For HD treatment, we know that cystatin C is substantially removed.6,19 Although no article on the usefulness of cystatin C in the setting of acute renal failure has been published, it might be suspected from the data published so far that cystatin C is not suitable for monitoring kidney function in acute renal failure. Concerning other new biomarkers for kidney function, it was demonstrated that NGAL is removed by HD treatment.20,21 Concerning low-flux HD, no significant reduction in serum cystatin C concentrations could be demonstrated.18,22 Because CAF has a substantially greater molecular mass than cystatin C it can be assumed that serum CAF concentrations are like cystatin C concentrations not influenced by low-flux HD, although this was not tested in our study. Thus, CAF should also be useful in monitoring residual renal function in patients receiving intermittent low-flux HD treatment. The cause why CAF was not removed in HD/Fx60 is not obvious. Because of the commercial technical information available both Fx60 and Elisio19H membranes have a similar sieving coefficient (0.28 vs. 0.223; Table IV, Supplementary material) for myoglobin (17 kDa). The material used for fiber production does not differ substantially. The higher surface area of Elisio19H (1.9 m2; see Table IV in Supplementary material) compared with Fx60 (1.4 m2; see Table IV in supplementary material) should not substantially
7
account for that finding but rather explains the difference of small solute clearance (creatinine and urea). The most plausible explanation for the difference is that the Elisio19H has a higher molecular weight cutoff and therefore provides better clearance for LMWPs with a molecular weight .20 kDa. Our investigation has following limitations: because of the study concept it was not performed as a crossover, randomized study and groups were neither matched nor adjusted for different parameters, so the results might be biased by different patient characteristics. Although no major differences were observed between groups, the 3 groups were not completely homogenous concerning, for example, ultrafiltration volume, treatment time, and predialytic parameter concentrations. Dialysate was not collected over the entire treatment period. However, the main focus of this study was to obtain a representative examination by collecting 4 samples. CONCLUSIONS
Q12
Serum CAF represents a biomarker that might be of additional value in the field of monitoring residual renal function of patients receiving extracorporeal treatment. This finding needs further investigation in larger patient populations; also, other HD membranes need to be evaluated. In the setting of AKI, it may serve as a biomarker to evaluate the recovery of kidney function during the phase of intermittent high-flux HD treatment, when Fx60 membrane is used. The same can be assumed for low-flux HD, although this was not tested in our study. Therefore, prospective studies addressing CAF as a biomarker for kidney function in AKI patients using reference methods such as iothalamate clearance need to be performed. Additionally, CAF might provide a promising representative LMWP to evaluate dialysis efficiency in the molecular weight range .20 kDa.
ACKNOWLEDGMENTS
The authors would thank Mrs Ursula Huber for excellent technical assistance and Mr Paul Albert, PhD, for revision of the manuscript. Stefan Hettwer and Pius Dahinden are currently employed by Neurotune AG, Schlieren, Switzerland. The authors further do not have any affiliations to the companies Fresenius Medical Care and Nipro Europe N.V. Conflict of interests: None. Supplementary Data
Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.trsl.2014.05.005.
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752
8
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806
Translational Research - 2014
Steubl et al
REFERENCES
Q13
1. Bellomo R, Kellum JA, Ronco C. Acute kidney injury. Lancet 2012;380:756–66. 2. do Nascimento GV, Gabriel DP, Abr~ao JM, Balbi AL. When is dialysis indicated in acute kidney injury? Ren Fail 2010;32: 396–400. 3. Palevsky PM. Renal replacement therapy in acute kidney injury. Adv Chronic Kidney Dis 2013;20:76–84. 4. De Smet R, Dhondt A, Eloot S, Galli F, Waterloos MA, Vanholder R. Effect of the super-flux cellulose triacetate dialyser membrane on the removal of non-protein-bound and proteinbound uraemic solutes. Nephrol Dial Transplant 2007;22:2006–12. 5. Basile C, Libutti P, Di Turo AL, et al. Removal of uraemic retention solutes in standard bicarbonate haemodialysis and long-hour slow-flow bicarbonate haemodialysis. Nephrol Dial Transplant 2011;26:1296–303. 6. Meert N, Eloot S, Schepers E, et al. Comparison of removal capacity of two consecutive generations of high-flux dialysers during different treatment modalities. Nephrol Dial Transplant 2011;26:2624–30. 7. Steubl D, Hettwer S, Vrijbloed W, et al. C-terminal agrin fragment (CAF)—a new fast biomarker for kidney function in renal transplant recipients. Am J Nephrol 2013;38:501–8. 8. Geddes CC, Traynor J, Walbaum D, Fox JG, Mactier RA. A new method of post-dialysis blood urea sampling: the ‘stop dialysate flow’method. Nephrol Dial Transplant 2000;15:517–23. 9. http://www.neurotune.com/downloads.html. 10. Finney H, Newman DJ, Gruber W, Merle P, Price CP. Initial evaluation of cystatin C measurement by particle enhanced immunonephelometry on the Behring nephelometer systems (BNA, BN II). Clin Chem 1997;43:1016–22. 11. Bergstr€ om J, Wehle B. No change in corrected beta 2-microglobulin concentration after cuprophane haemodialysis. Lancet 1987;1:628–9. 12. Troidle L, Finkelstein F, Hotchkiss M, Leypoldt JK. Enhanced solute removal with intermittent, in-center, 8-hour nocturnal hemodialysis. Hemodial Int 2009;13:487–91.
13. Leypoldt JK, Cheung AK, Deeter RB. Single compartment models for evaluating beta 2-microglobulin clearance during hemodialysis. ASAIO J 1997;43:904–9. 14. Cheung AK, Agodoa LY, Daugirdas JT, et al. Effects of hemodialyzer reuse on clearances of urea and beta2-microglobulin. The Hemodialysis (HEMO) Study Group. J Am Soc Nephrol 1999; 10:117–27. 15. Watson PE, Watson ID, Batt RD. Total body water volumes for adult males and females estimated from simple anthropometric measurements. Am J Clin Nutr 1980;33:27–39. 16. Balık M, Jabor A, Waldauf P, et al. Cystatin C as a marker of residual renal function during continuous hemodiafiltration. Kidney Blood Press Res 2005;28:14–9. 17. Baas MC, Bouman CS, Hoek FJ, Krediet RT, Schultz MJ. Cystatin C in critically ill patients treated with continuous venovenous hemofiltration. Hemodial Int 2006;10(Suppl 2):S33–7. 18. Lindstr€om V, Grubb A, Alquist Hegbrant M, Christensson A. Different elimination patterns of beta-trace protein, beta2microglobulin and cystatin C in haemodialysis, haemodiafiltration and haemofiltration. Scand J Clin Lab Invest 2008;68: 685–91. 19. Tian S, Kusano E, Ohara T, et al. Cystatin C measurement and its practical use in patients with various renal diseases. Clin Nephrol 1997;48:104–8. 20. Bolignano D, Coppolino G, Romeo A, Lacquaniti A, Buemi M. Neutrophil gelatinase-associated lipocalin levels in chronic haemodialysis patients. Nephrology (Carlton) 2010;15:23–6. 21. Malyszko J, Malyszko JS, Koc-Zorawska E, Kozminski P, Mysliwiec M. Neutrophil gelatinase-associated lipocalin in dialyzed patients is related to residual renal function, type of renal replacement therapy and inflammation. Kidney Blood Press Res 2009;32:464–9. 22. Krishnamurthy N, Arumugasamy K, Anand U, et al. Effect of hemodialysis on circulating cystatin c levels in patients with end stage renal disease. Indian J Clin Biochem 2010; 25:43–6.
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860
ORIGINAL ARTICLE Q1
Q14
Influence of high-flux hemodialysis and hemodiafiltration on serum C-terminal agrin fragment levels in end-stage renal disease patients DOMINIK STEUBL, STEFAN HETTWER, PIUS DAHINDEN, PETRA WOLF, PETER LUPPA, € CARSTEN A. WAGNER, CLAUDIUS KUCHLE, CHRISTOPH SCHMADERER, LUTZ RENDERS, UWE HEEMANN, and MARCEL ROOS € MUNCHEN, GERMANY AND ZURICH, SWITZERLAND
Q3
Q4
C-terminal agrin fragment (CAF, 22 kDa) has been shown to be a promising new rapid biomarker for kidney function. This study evaluated the influence of hemodialysis (HD) and hemodiafiltration (HDF) treatment on serum CAF concentrations in patients with end-stage renal disease (ESRD). A total of 36 patients with ESRD undergoing chronic HD/HDF treatment were enrolled (21 high-flux-HD/Fx60 membrane, 7 highflux-HD/Elisio19H membrane, and 8 HDF/Elisio19H membrane). On a midweek session, blood samples were obtained before, at halftime, and post-treatment. Dialysate samples were obtained 4 times during treatment. Serum and dialysate CAF, cystatin C, urea, and creatinine concentrations were measured. Reduction ratios (RRs), total solute removal, overall dialytic clearance, and instantaneous dialytic clearance at halftime were calculated and compared. Although HD/Elisio19H and HDF/ Elisio19H treatments significantly reduced CAF concentrations (RR 46.6 6 9.1% and 57.6 6 11.7%, respectively, P 5 0.018 and P 5 0.001), HD/Fx60 treatment did not remove CAF from serum (RR 2.4 6 15.4%, P 5 0.25), there was no relevant CAF detection in dialysate. In the HD/Fx60 group, the RR of CAF was significantly lower compared with cystatin C, urea, and creatinine, in which significant removal was detected (37.9 6 14.8%, 65.0 6 10.7%, and 56.0 6 9.8%, respectively, P , 0.001). CAF is a new biomarker for kidney function whose serum concentration is not influenced by conventional high-flux HD using Fx60 membrane. It might therefore represent a promising dialysis-independent biomarker for evaluation of kidney function, for example, in acute kidney failure. (Translational Research 2014;-:1–8) Abbreviations: AKI ¼ acute kidney injury; BW ¼ body weight; CAF ¼ C-terminal agrin fragment; ECV ¼ extracellular volume; ESRD ¼ end-stage renal disease; HD ¼ hemodialysis; HDF ¼ hemodiafiltration; IDC ¼ instantaneous dialytic clearance; LMWP ¼ low-molecular-weight protein; ODC ¼ overall dialytic clearance; RR ¼ reduction ratio; TSR ¼ total solute removal; UF ¼ ultrafiltration
From the Abteilung f€ur Nephrologie, Klinikum rechts der Isar, M€ unchen, Germany; Neurotune AG, Schlieren-Zurich, Switzerland; Institut f€ ur Medizinische Statistik und Epidemiologie, Klinikum rechts der Isar, M€ unchen, Germany; Institut f€ur Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, M€unchen, Germany; Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
Reprint requests: Dominik Steubl, Department of Nephrology, Klinikum rechts der Isar, Ismaninger Street 22 D-81675 M€unchen, Germany; e-mail: [email protected]. 1931-5244/$ - see front matter Ó 2014 Mosby, Inc. All rights reserved. http://dx.doi.org/10.1016/j.trsl.2014.05.005
Submitted for publication March 6, 2014; revision submitted May 8, 2014; accepted for publication May 10, 2014.
1 FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104
2
105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158
Translational Research - 2014
Steubl et al
AT A GLANCE COMMENTARY Steubl D, et al. Background
The evaluation of residual renal function in patients undergoing extracorporeal treatment is difficult to assess because conventional biomarkers are eliminated by dialysis. We evaluated C-terminal agrin fragment (CAF), which was shown to be a new biomarker for kidney function in another study, in hemodialysis treatment. We showed that CAF is not eliminated by conventional highflux hemodialysis. Translational Significance
CAF, originally characterized in basic neuroscience, is a new dialysis-independent biomarker for kidney function and might therefore be of additive value in the field of clinical nephrology.
INTRODUCTION
Q5
Acute kidney failure (AKI) and chronic kidney disease are important problems in various clinical settings, leading to the accumulation of uremic toxins, electrolyte disturbances, fluid overload and changes in acid-base homeostasis.1 Often extracorporeal treatment such as hemodialysis (HD) and hemofiltration is required acutely or as chronic renal replacement therapy.2,3 Once extracorporeal treatment has been initiated, the judgment if and to what extent renal function regenerates or further decreases is impeded by the fact that the routinely used serum biomarkers of renal function, such as serum creatinine, urea, or cystatin C, are eliminated by extracorporeal treatment.4-6 Therefore, clinicians must rely on inaccurate markers such as urinary output. A definitive decision on the current situation of renal function requires discontinuation of extracorporeal treatment followed by monitoring of serum creatinine, urea, and cystatin C concentrations. This approach generates additional costs, consumes time, and might put the patient at risk. Therefore, a serum marker that monitors kidney function unaffected by extracorporeal treatment would be desirable. Recently, we characterized serum C-terminal agrin fragment (CAF), a 22 kDa protein derived from agrin, as a new biomarker for kidney function.7 It correlates with serum creatinine concentrations (logarithmic correlation r 5 0.74) and eGFR (logarithmic correlation r 5 20.77), and reacts more rapidly to changes in renal function than creatinine. Because of CAF’s molecular
weight of 22 kDa, we hypothesized that serum CAF concentrations might not be significantly influenced by extracorporeal treatment using high-flux dialyzers, preliminary data confirmed this assumption. The present study evaluated the time course of serum CAF concentrations under different treatment modalities (HD and hemodiafiltration [HDF]) in chronic HD patients using 2 different high-flux membranes and compared it with 3 markers of kidney function: creatinine, urea, and cystatin C. The aim of the survey was not to evaluate CAF as a biomarker for kidney function. This was already proven in the former study.7 Instead the aim was uniquely to assess the influence of different extracorporeal treatments on serum CAF concentrations. We chose a group of patients with a daily urinary output of less that 500 mL because we assumed that the average urine production during a 5-hour HD session should not exceed a maximum of 100 mL, and we know from another study (unpublished data) that the Q6 renal clearance of CAF in patients with a daily urinary output of 100 mL is negligible. Thereby, we wanted to minimize the confounding factor of relevant endogenous renal clearance of CAF during HD treatment that might influence the difference between pre- and postserum CAF levels. Changes should only rely on clearance via the HD treatment. MATERIALS AND METHODS Study design and patients. The study was approved by the local Ethics Approval Committee (Klinikum rechts der Isar, Technische Universit€at, Munich, Germany) and is in line with the declaration of Helsinki. All patients enrolled in this study gave their informed consent. The study was performed with a cross-sectional, noncrossover, nonrandomized, open-label proof-ofprinciple design. The group is a representative sample of the chronic dialysis collective at our center. The groups were not matched for certain parameters; patients were not assigned to a treatment group intentionally. The reason why patients received a certain treatment was based on medical reasons such as insufficient kt/V levels or membrane intolerance. No specific inclusion or exclusion criteria had to be met. A total of 36 stable, adult oliguric/anuric HD patients Q7 (23 males, 13 females, mean age 62.6 6 16.6 years) who had been on chronic thrice-weekly maintenance HD/HDF treatment for at least 3 months without acute illness were enrolled. The primary underlying diseases were diabetic nephropathy (n 5 4), renal vascular disease (n 5 5), immunologic disorders (n 5 8), autosomal-dominant polycystic kidney disease (n 5 2), cardiorenal syndrome (n 5 2), and others (including unknown cases, n 5 15).
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212
Translational Research Volume -, Number -
213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266
Steubl et al
In all patients serum and dialysate samples were taken at a midweek session. Primary outcome parameter was the removal of CAF, creatinine, urea, and cystatin C from serum in the form of reduction ratio (RR). Secondary outcomes included intradialytic changes in serum and dialysate concentrations, total solute removal (TSR), instantaneous dialytic clearance (IDC) at halftime, and in case of CAF and cystatin C, overall dialytic clearance (ODC). Treatment and technique characteristics. All patients received treatment with either a Fresenius 4008H or 5008H machine (Fresenius Medical Care, Bad Homburg, Germany; Table I) in a 2-needle mode. Vascular access was arteriovenous fistula in 30 patients (native in 26, synthetic graft in 4) and central venous catheter in 6 patients. All patients had a sufficient HD dose, indicated by a kt/V . 1.2 in a previous measurement. Twenty-eight patients received high-efficiency, highflux, and high-permeability HD. In 21 of these patients an Fx60 membrane (high-flux polysulfone membrane; Fresenius Medical Care) was used (group named HD/ Fx60), 7 (group named HD/E19H) received treatment using an Elisio19H membrane (high-flux Polynephron membrane; Nipro Europe N.V., Zaventem, Belgium). Treatment duration ranged between 3.5 and 5 hours, and the effective blood flow between 200 and 300 mL/ min. The dialysate flow was set to 500 mL/min in every patient. Eight patients received postdilution HDF treatment using an Elisio19H dialyzer (group named HDF/E19H). Treatment ranged from 4.5 to 5 hours, and blood flow from 250 to 280 mL/min. The dialysate flow was 500 mL/min in every patient. A description of patients’ demographics and treatments can be found in Table II. Membrane characteristics are listed in Table IV (Supplementary material). Sample collection and laboratory analysis. Blood samples were obtained before initiation of treatment, at halftime, and after cessation of treatment. Pre- (cserum-pre) and post-treatment (cserum-post) samples were obtained directly from the vascular access. The post-treatment sample was collected 2 minutes after the blood pump had been set to 50 mL/min followed by a stop of the pump.8 The half-time sample (cserum-1/2) was collected directly from the arterial tubing. Dialysate was collected directly from the effluent tubing 1 minute after the initiation of treatment (cdial-pre), after 1 hour (cdial-1h), at halftime (cdial-1/2), and 1 minute before the cessation of treatment (cdial-post). Blood samples were centrifuged at 3000 rpm for 8 minutes, then the serum was collected and both serum and dialysate stored at 280 C until analysis was performed. Analysis included measurement of CAF, creatinine, urea, and cystatin C concentrations. CAF concentrations were measured using a commercially available
3
Table I. Patient’s and treatment characteristics Parameter
HD/Fx60
HD/Elisio19H
HDF/Elisio19H
Gender 14/7 4/3 6/2 (male/female) Age (y) 62.1 6 17.7 67.6 6 18.1 59.6 6 9.7 Machine (Fresenius 12/9 0/7 1/7 4008/5008) Anticoagulation 14/7 7/0* 8/0* (Hep./citrate) BWpre (kg) 69.0 6 14.7 75.5 6 14.4 82.9 6 17.1 68.5 6 14.7 74.0 6 14.0 80.5 6 17.0 BWpost (kg) UFV (L) 1.0 6 0.9 1.9 6 1.0* 3.0 6 0.7* t (h) 4.0 6 0.4 4.1 6 0.6 4.9 6 0.2*† QB (mL/min) 240 6 34 253 6 22 261 6 11 Substitution — — 65.3 6 2.8 volume (mL/min) CBF (L) 55.2 6 12.1 61.7 6 8.0 73.7 6 3.2 QD (mL/min) 500 6 0 500 6 0 500 6 0 CDF (L) 117.0 6 18.0 125.0 6 17.3 146.3 6 6.5 Abbreviations: BWpre, body weight before treatment; BWpost, body weight after treatment; CBF, cumulative blood flow; CDF, cumulative dialysate flow; Hep, heparin; QB, blood flow; QD, dialysate flow; t, treatment duration; UFV, ultrafiltration volume. *P , 0.05 vs HD/Fx60. † P , 0.05 vs HD/Elisio19H.
enzyme-linked immunosorbent assay kit (NTCAF Elisa Kit; Neurotune, Schlieren, Switzerland) as described previously.7,9 Creatinine and urea were quantified by photometric techniques (creatinine, normal range 0.7–1.3 mg/dL in males and 0.5–1.1 mg/dL in females; urea, normal range 7–18 mg/dL). Cystatin C concentrations were determined using a nephelometric, latex-enhanced assay kit from Siemens Healthcare Diagnostics (Eschborn, Germany). The measurements were performed on an automated BN Prospec nephelometer from Siemens.10 Calculations. For the low-molecular-weight proteins (LMWPs), CAF and cystatin C cserum-1/2 and cserum-post were corrected for extracellular volume (ECV) changes.11 cserum-post was corrected for the difference in the patient’s pretreatment body weight (BWpre) and post-treatment body weight (BWpost) according to the formula11 cserumpost=corr 5 cserumpost 11 BWpre 2BWpost 0:2 3 BWpost : For cserum-1/2 we assumed that the BW, although not measured, would be half of the difference between BWpre and BWpost leading to the following formula: cserum1=2=corr 5 cserum1=2 11 BWpre 2 BWpost 2 1 BWpost 0:2 3 BWpost : 2 1 BWpost
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320
4
321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374
Translational Research - 2014
Steubl et al
Table II. Serum levels and RRs Parameter
Creatinine (mg/dL) HD/Fx60 HD/Elisio19H HDF/Elisio19H Urea (mg/dL) HD/Fx60 HD/Elisio19H HDF/Elisio19H Cystatin C (mg/L) HD/Fx60 HD/Elisio19H HDF/Elisio19H CAF (pmol) HD/Fx60 HD/Elisio19H HDF/Elisio19H
cserum-pre
cserum-½
cserum-post
RRpre-1/2 (%)
RRpre-post (%)
5.3 6 1.9 6.5 6 1.3 9.4 6 1.3†
2.9 6 0.9 3.1 6 0.6 4.4 6 0.8
2.1 6 0.7 2.0 6 0.5 3.1 6 0.8
40.9 6 10.4 49.4 6 6.7 48.9 6 4.9
56.0 6 9.8* 65.1 6 6.5* 60.3 6 7.7
39.6 6 15.5 54.3 6 14.2 45.3 6 13.7
19.4 6 7.5 22.7 6 6.2 18.6 6 5.9
11.8 6 4.2 12.5 6 4.0 11.6 6 4.4
46.4 6 11.6 55.3 6 6.7 55.4 6 3.7
65.0 6 10.7‡ 74.1 6 5.5‡ 70.7 6 5.6
4.1 6 1.3 4.6 6 0.8 4.4 6 1.1
2.8 6 0.9 2.3 6 0.5 2.2 6 0.6
2.5 6 0.7 1.7 6 0.2 1.4 6 0.5
30.8 6 13.3 49.7 6 12.7 50.4 6 8.5
37.9 6 14.8§ 61.1 6 10.1 69.3 6 6.9
1508.7 6 709.3 1167.2 6 574.9 598.9 6 354.9
4.0 6 13.3 35.6 6 13.5 46.1 6 11.1
2.4 6 15.4§ 46.6 6 9.1i 57.6 6 11.7i
1527.8 6 904.5 2196.0 6 1023.1 1467.8 6 946.9
1522.70 6 705.3 1380.4 6 674.9 771.3 6 439.3
Abbreviations: CAF, C-terminal agrin fragment; cserum-pre, serum concentration before treatment; cserum-½, serum concentration at halftime of treatment; cserum-post, serum concentration at the end of treatment; HD, hemodialysis; HDF, hemodiafiltration; RRpre-1/2, reduction ratio at halftime of treatment to before treatment; RRpre-post, reduction ratio at the end of treatment to before treatment. *P 5 0.013. † P , 0.05 vs cserum-pre HD/Fx60/HD/Elisio19H. ‡ P 5 0.026. § P , 0.001 vs HD/Elisio19H/HDF/Elisio19H. i P 5 0.04.
The RR from pretreatment to half-time treatment (RRpre-1/2) and from pretreatment to post-treatment (RRpre-post) for CAF and cystatin C were calculated according to the formula6 RR ð%Þ5 cserumpre 2cserumpost=corr cserumpre 3 100: Analogous to the RR for creatinine and urea were calculated according to the formula: RR ð%Þ5 cserumpre 2 cserumpost cserumpre 3 100: To assess an IDC of all substances at halftime of treatment, dialytic-sided clearance was calculated according to the following formula12: IDCðmL=minÞ5 cdial1=2 3 QD cserum1=2 ; where QD is the dialysate flow in milliliter per minute. Similar to b2-microglobulin, we used the single compartment model of Leypoldt et al. for calculation of an overall extracorporeal clearance of CAF and cystatin C13,14: ODC 5 QUF 3 12ln cserumpost cserumpre ln 3 1 1 UF ECVpost : In this formula, QUF represents the hourly ultrafiltration rate derived from the difference of pre- and posttreatment body weight. UF represents the total ultrafil-
tration volume, calculated from QUF and the treatment time. Postdialytic extracellular fluid (ECVpost) was Q8 assumed to be one-third of total body water.14 The total body water was calculated according to the anthropometric measurements reflecting age, height, and weight of the patient.15 The solute concentration time curves in serum and dialysate were used to calculate the area under the curve using the trapezoidal method. These data were multiplied by the accumulated volume and the corresponding amount of time to obtain the TSR. Statistical analysis. For statistical analysis IBM SPSS 20 and R 2.15.1 (R Foundation for Statistical Computing, Vienna, Austria) were used. The KolmogorovSmirnov test was performed to evaluate the normality of data distribution. Continuous data are expressed as the mean with standard deviation (SD), and categorical variables are reported in absolute numbers and percentages. Categorical baseline variables between the groups were compared using chi-square test. For comparison of RR, IDC, and ODC of CAF, cystatin C, urea, and creatinine within 1 extracorporeal treatment method/1 patient the Wilcoxon-Rank test was used. Q9 To compare continuous variables between the groups as well as RR, IDC, and ODC of 1 biomarker between the groups, the Mann-Whitney U test was performed. All analyses were done using a 2-sided 0.05 level of significance and have not been adjusted for multiple testing.
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428
Translational Research Volume -, Number -
429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482
Steubl et al
5
Fig 1. (A) RRs of different biomarkers compared within 1 extracorporeal procedure. Values are presented as the mean and standard deviation. (B) RRs of different biomarkers compared between 3 different extracorporeal procedures. Values are presented as the mean and standard deviation. CAF, C-terminal agrin fragment; CyC, cystatin C; Crea, creatinine; Fx60 HD, hemodialysis treatment performed with Fx60 membrane; Elisio HD, hemodialysis treatment performed with Elisio19H membrane; Elisio HDF, hemodiafiltration treatment performed with Elisio19H membrane; RR, reduction ratio.
RESULTS Baseline characteristics of the treatment groups.
According to the patients’ personal and treatment parameters in the group HD/Fx60, the total ultrafiltration volume was significantly lower than in HD/E19H and HDF/E19H (P , 0.05; Table I). Compared with HDF/E19H, the treatment time was significantly shorter in HD/Fx60 and HD/E19H (P , 0.05; Table I). In HD/Fx60 significantly more patients received citrate anticoagulation compared with HD/E19H and HDF/E19H (Table I). Apart from this, the groups were comparable without any further statistically significant differences. Clearance
of
small
water-soluble
substances.
Pretreatment serum creatinine concentrations were comparable between HD/Fx60 and HD/E19H but were significantly higher in HDF/E19H (P , 0.05; Table II). In all treatment groups, serum creatinine concentrations decreased significantly by 56.0%, 65.1%, and 60.3%, respectively (HD/Fx60 [P , 0.001], HD/E19H [P 5 0.018], HDF/E19H [P 5 0.012]; Table II, Fig 1, B). The reduction was only significantly greater in HD/ E19H compared with HD/Fx60 (P 5 0.013). Pretreatment urea concentrations were not significantly different between the groups. In all groups, there
was a significant reduction in urea concentrations of 65.0%, 74.1%, and 70.7%, respectively (HD/Fx60 [P , 0.001], HD/E19H [P 5 0.018], HDF/E19H [P 5 0.001]; Table II, Fig 1, B). The reduction was significantly greater only in HD/E19H compared with HD/Fx60 (P 5 0.026). Clearance of LMWPs. Pretreatment cystatin C concentrations were not significantly different between the groups. A significant reduction could be detected in all groups, resulting in RR of 37.9% (P , 0.001) in HD/ Fx60, 61.1% (P 5 0.001) in HD/E19H, and 69.3% in HDF/E19H (P 5 0.012; Table II, Fig 1, B). RR in HD/ E19H and HDF/E19H was significantly greater than in HD/Fx60 (P , 0.001 in both cases; Table II, Fig 1, B), whereas it did not differ significantly between HD/ E19H and HDF/E19H (P 5 0.094; Table II, Fig 1, B). Pretreatment CAF concentrations did not differ significantly between the 3 groups. A significant reduction was reached in HD/E19H and HDF/E19H (46.6% and 57.6%, P 5 0.018 and P 5 0.001, respectively; Table II, Fig 1, B), whereas in HD/Fx60 no significant reduction in CAF serum concentrations was seen (2.4%, P 5 0.25; Table II, Fig 1, B). Consequently, the RR was significantly lower in HD/Fx60 compared with HD/E19H and HDF/E19H (P , 0.001 in both
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536
6
537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590
Translational Research - 2014
Steubl et al
Table III. Dialysate levels, total solute removal, and dialytic clearances Parameter
Q2
Creatinine (mg/dL) Fx60-HD (G1) Elisio19H-HD (G2) (G3) Urea (mg/dL) Fx60-HD (G1) Elisio19H-HD (G2) Elisio19H-HDF (G3) CAF (pmol) Fx60-HD (G1) Elisio19H-HD (G2) Elisio19H-HDF (G3) Cystatin C (mg/L) Fx60-HD (G1) Elisio19H-HD (G2) Elisio19H-HDF (G3)
t50
t51h
t5½
t51
1.1 6 0.6 1.7 6 0.5 1.8 6 0.4
1.0 6 0.5 1.3 6 0.3 1.8 6 0.3
0.8 6 0.3 0.9 6 0.2 1.2 6 0.3
0.5 6 0.3 0.6 6 0.2 0.9 6 0.3
10.3 6 4.6 15.7 6 1.0 11.0 6 3.8
9.0 6 4.5 13.0 6 3.0 10.1 6 3.3
7.8 6 5.3 8.3 6 2.6 6.7 6 2.6
13.8 6 13.3 40.4 6 17.0 88.0 6 33.2
7.1 6 8.4 26.9 6 23.3 51.5 6 20.6
0.17 6 0.07 0.38 6 0.14 0.42 6 0.17
0.14 6 0.06 0.29 6 0.04 0.40 6 0.08
TSR (mg)
ODC (mL/min)
IDC (mL/min)
709.6 6 349.7 959.4 6 337.2 1715.4 6 342.1
— — —
130.1 6 32.1 137.9 6 25.6 121.3 6 18.5
4.3 6 3.6 4.7 6 1.9 5.0 6 1.7
3938.3 6 2363.8 5643.7 6 2392.6 6627.7 6 2092.8
— — —
167.0 6 40.1 173.9 6 42.2 164.0 6 28.3
6.1 6 7.0 24.7 6 20.2 36.5 6 8.8
7.5 6 9.3 16.1 6 9.9 28.4 6 8.3
0.01 6 0.01 0.05 6 0.05 0.11 6 0.03
2.1 6 8.0 34.9 6 9.9 49.5 6 21.3
3.6 6 4.6 17.6 6 3.1 28.8 6 15.0
0.10 6 0.04 0.18 6 0.07 0.24 6 0.08
0.09 6 0.03 0.14 6 0.06 0.16 6 0.08
9.90 6 4.72 21.20 6 8.26 35.88 6 8.48
21.2 6 16.6 52.1 6 12.4 64.9 6 17.0
18.2 6 5.7 39.2 6 16.8 50.0 6 10.9
Abbreviations: CAF, C-terminal agrin fragment; HD, hemodialysis; HDF, hemodiafiltration; IDC, instantaneous dialytic-sided clearance at 1 hour of treatment; ODC, overall dialytic clearance; TSR, total solute removal; t 5 0, before treatment; t 5 1 h, after 1 hour of treatment; t 5 ½, at halftime of treatment; t 5 1, at the end of treatment.
cases; Table II, Fig 1, B). RR of CAF was significantly higher in HDF/E19H compared with HD/E19H (P 5 0.04; Table II, Fig 1, B). Comparison of RRs of CAF and the other biomarkers within the 3 treatment modalities. When we compared
the RR of CAF with the other biomarkers within the 3 treatment modalities, the RR of CAF in HD/Fx60 was significantly lower compared with cystatin C, creatinine, and urea (2.4% vs 37.9%, 56.0%, and 65.0%, respectively, P , 0.001 in all cases; Table II, Fig 1, A). In HD/E19H, the RR of CAF was significantly lower compared with creatinine and urea (46.6% vs. 65.1% and 74.1% respectively, P 5 0.018; Table II, Fig 1, A), but not to cystatin C (46.6% vs 61.1%, P 5 0.063; Table II, Fig 1, A). In HDF/E19H, the RR of CAF was significantly lower than of cystatin C and urea (57.6% vs 69.3% and 70.7%, respectively, P 5 0.05 and P 5 0.025; Table II, Fig 1, A), whereas there was no significant difference between CAF and creatinine (57.6% vs 60.3%; P 5 0.58, Table II, Fig 1, A). TSR of CAF in the 3 treatment modalities. CAF was most effectively removed by HDF/E19H (0.11 mg) compared with HD/Fx60 (0.01 mg, P , 0.001) and HD/E19H (0.05 mg, P 5 0.021). HD/E19H was significantly more effective than HD/Fx60 (P 5 0.003; Table III). The TSR of the other 3 biomarkers can be found in Table III. ODC of CAF. The ODC of CAF was highest in the HDF group (49.5 mL/min) compared with HD/Fx60 (2.1 mL/min, P , 0.001) and HD/E19H (34.9 mL/ min, P 5 0.152). ODC of CAF was significantly higher in HD/E19H compared with HD/Fx60 (P , 0.001).
Comparing CAF and cystatin C, the ODC of cystatin C was significantly higher than the ODC of CAF in HD/ Fx60 and HDF/E19H (21.2 vs 2.1 mL/min, P 5 0.001 and 64.9 vs 49.5 mL/min, P 5 0.05 respectively; Table III), whereas it was not significantly different in HD/E19H (52.1 vs 34.9 mL/min, P 5 0.063, Table III). Instantaneous dialytic-sided clearance at halftime of treatment. IDC of CAF was significantly higher
in HDF/E19H compared with both HD/Fx60 (28.8 vs 3.6 mL/min, P , 0.001) and HD/E19H (17.6 mL/min, P 5 0.005). IDC of HD/E19H was significantly higher compared with HD/Fx60 (P 5 0.042; Table III). The IDCs of the other 3 biomarkers in the different treatment procedures can be found in Table III. DISCUSSION
This is the first study to evaluate the influence of extracorporeal treatment on CAF serum concentrations and to compare it with other serum biomarkers of kidney function, urea, creatinine, and cystatin C. Therefore, the aim of the study was not to assess CAF as a biomarker for kidney function in this group of patients but only focus on extracorporeal elimination. We evaluated HD treatment using 2 different membranes, Fx60 and Elisio19H, and HDF treatment using an Elisio19H membrane. We could demonstrate that, in contrast to cystatin C, urea, and creatinine, serum CAF concentrations are not significantly influenced by high-flux HD treatment using an Fx60 membrane. Besides this major finding, we also detected that the Elisio 19H is highly efficient in removing LMWPs up to the size of 22 kDa in regular HD treatment, although HD was inferior to HDF using
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644
Translational Research Volume -, Number -
645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698
Q10
Q11
Steubl et al
the same membrane concerning CAF removal, whereas HD treatment was superior to HDF treatment concerning creatinine and urea removal. Because instantaneous dialytic-sided clearance allowed us to detect a substantial amount of CAF in the dialytic fluid, we demonstrated that the reduction in CAF serum concentrations was mainly because of real removal instead of adsorption to the membrane surface. Our results show that high-flux HD using Fx60 was unable to remove CAF from patient’s blood, as demonstrated by different parameters such as RR, IDC, ODC, and TSR. CAF might therefore represent a promising biomarker to monitor residual renal function unaffected from intermittent high-flux HD with Fx60 membrane, although the topic ‘‘CAF as a biomarker for residual renal function’’ was not tested in this study but is already shown earlier.7 Furthermore, we could show that urea, creatinine, and cystatin C were substantially removed by intermittent high-flux HD using both Fx60 and Elisio19H membranes. Although cystatin C has been advocated to be useful for monitoring residual kidney function in critically ill patients receiving hemofiltration and HDF,16,17 in both studies as well as another study investigating hemofiltration and HDF18 a relevant elimination of cystatin C was detected. So it has to be questioned if this assumption really holds true for larger populations. For HD treatment, we know that cystatin C is substantially removed.6,19 Although no article on the usefulness of cystatin C in the setting of acute renal failure has been published, it might be suspected from the data published so far that cystatin C is not suitable for monitoring kidney function in acute renal failure. Concerning other new biomarkers for kidney function, it was demonstrated that NGAL is removed by HD treatment.20,21 Concerning low-flux HD, no significant reduction in serum cystatin C concentrations could be demonstrated.18,22 Because CAF has a substantially greater molecular mass than cystatin C it can be assumed that serum CAF concentrations are like cystatin C concentrations not influenced by low-flux HD, although this was not tested in our study. Thus, CAF should also be useful in monitoring residual renal function in patients receiving intermittent low-flux HD treatment. The cause why CAF was not removed in HD/Fx60 is not obvious. Because of the commercial technical information available both Fx60 and Elisio19H membranes have a similar sieving coefficient (0.28 vs. 0.223; Table IV, Supplementary material) for myoglobin (17 kDa). The material used for fiber production does not differ substantially. The higher surface area of Elisio19H (1.9 m2; see Table IV in Supplementary material) compared with Fx60 (1.4 m2; see Table IV in supplementary material) should not substantially
7
account for that finding but rather explains the difference of small solute clearance (creatinine and urea). The most plausible explanation for the difference is that the Elisio19H has a higher molecular weight cutoff and therefore provides better clearance for LMWPs with a molecular weight .20 kDa. Our investigation has following limitations: because of the study concept it was not performed as a crossover, randomized study and groups were neither matched nor adjusted for different parameters, so the results might be biased by different patient characteristics. Although no major differences were observed between groups, the 3 groups were not completely homogenous concerning, for example, ultrafiltration volume, treatment time, and predialytic parameter concentrations. Dialysate was not collected over the entire treatment period. However, the main focus of this study was to obtain a representative examination by collecting 4 samples. CONCLUSIONS
Q12
Serum CAF represents a biomarker that might be of additional value in the field of monitoring residual renal function of patients receiving extracorporeal treatment. This finding needs further investigation in larger patient populations; also, other HD membranes need to be evaluated. In the setting of AKI, it may serve as a biomarker to evaluate the recovery of kidney function during the phase of intermittent high-flux HD treatment, when Fx60 membrane is used. The same can be assumed for low-flux HD, although this was not tested in our study. Therefore, prospective studies addressing CAF as a biomarker for kidney function in AKI patients using reference methods such as iothalamate clearance need to be performed. Additionally, CAF might provide a promising representative LMWP to evaluate dialysis efficiency in the molecular weight range .20 kDa.
ACKNOWLEDGMENTS
The authors would thank Mrs Ursula Huber for excellent technical assistance and Mr Paul Albert, PhD, for revision of the manuscript. Stefan Hettwer and Pius Dahinden are currently employed by Neurotune AG, Schlieren, Switzerland. The authors further do not have any affiliations to the companies Fresenius Medical Care and Nipro Europe N.V. Conflict of interests: None. Supplementary Data
Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.trsl.2014.05.005.
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752
8
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806
Translational Research - 2014
Steubl et al
REFERENCES
Q13
1. Bellomo R, Kellum JA, Ronco C. Acute kidney injury. Lancet 2012;380:756–66. 2. do Nascimento GV, Gabriel DP, Abr~ao JM, Balbi AL. When is dialysis indicated in acute kidney injury? Ren Fail 2010;32: 396–400. 3. Palevsky PM. Renal replacement therapy in acute kidney injury. Adv Chronic Kidney Dis 2013;20:76–84. 4. De Smet R, Dhondt A, Eloot S, Galli F, Waterloos MA, Vanholder R. Effect of the super-flux cellulose triacetate dialyser membrane on the removal of non-protein-bound and proteinbound uraemic solutes. Nephrol Dial Transplant 2007;22:2006–12. 5. Basile C, Libutti P, Di Turo AL, et al. Removal of uraemic retention solutes in standard bicarbonate haemodialysis and long-hour slow-flow bicarbonate haemodialysis. Nephrol Dial Transplant 2011;26:1296–303. 6. Meert N, Eloot S, Schepers E, et al. Comparison of removal capacity of two consecutive generations of high-flux dialysers during different treatment modalities. Nephrol Dial Transplant 2011;26:2624–30. 7. Steubl D, Hettwer S, Vrijbloed W, et al. C-terminal agrin fragment (CAF)—a new fast biomarker for kidney function in renal transplant recipients. Am J Nephrol 2013;38:501–8. 8. Geddes CC, Traynor J, Walbaum D, Fox JG, Mactier RA. A new method of post-dialysis blood urea sampling: the ‘stop dialysate flow’method. Nephrol Dial Transplant 2000;15:517–23. 9. http://www.neurotune.com/downloads.html. 10. Finney H, Newman DJ, Gruber W, Merle P, Price CP. Initial evaluation of cystatin C measurement by particle enhanced immunonephelometry on the Behring nephelometer systems (BNA, BN II). Clin Chem 1997;43:1016–22. 11. Bergstr€ om J, Wehle B. No change in corrected beta 2-microglobulin concentration after cuprophane haemodialysis. Lancet 1987;1:628–9. 12. Troidle L, Finkelstein F, Hotchkiss M, Leypoldt JK. Enhanced solute removal with intermittent, in-center, 8-hour nocturnal hemodialysis. Hemodial Int 2009;13:487–91.
13. Leypoldt JK, Cheung AK, Deeter RB. Single compartment models for evaluating beta 2-microglobulin clearance during hemodialysis. ASAIO J 1997;43:904–9. 14. Cheung AK, Agodoa LY, Daugirdas JT, et al. Effects of hemodialyzer reuse on clearances of urea and beta2-microglobulin. The Hemodialysis (HEMO) Study Group. J Am Soc Nephrol 1999; 10:117–27. 15. Watson PE, Watson ID, Batt RD. Total body water volumes for adult males and females estimated from simple anthropometric measurements. Am J Clin Nutr 1980;33:27–39. 16. Balık M, Jabor A, Waldauf P, et al. Cystatin C as a marker of residual renal function during continuous hemodiafiltration. Kidney Blood Press Res 2005;28:14–9. 17. Baas MC, Bouman CS, Hoek FJ, Krediet RT, Schultz MJ. Cystatin C in critically ill patients treated with continuous venovenous hemofiltration. Hemodial Int 2006;10(Suppl 2):S33–7. 18. Lindstr€om V, Grubb A, Alquist Hegbrant M, Christensson A. Different elimination patterns of beta-trace protein, beta2microglobulin and cystatin C in haemodialysis, haemodiafiltration and haemofiltration. Scand J Clin Lab Invest 2008;68: 685–91. 19. Tian S, Kusano E, Ohara T, et al. Cystatin C measurement and its practical use in patients with various renal diseases. Clin Nephrol 1997;48:104–8. 20. Bolignano D, Coppolino G, Romeo A, Lacquaniti A, Buemi M. Neutrophil gelatinase-associated lipocalin levels in chronic haemodialysis patients. Nephrology (Carlton) 2010;15:23–6. 21. Malyszko J, Malyszko JS, Koc-Zorawska E, Kozminski P, Mysliwiec M. Neutrophil gelatinase-associated lipocalin in dialyzed patients is related to residual renal function, type of renal replacement therapy and inflammation. Kidney Blood Press Res 2009;32:464–9. 22. Krishnamurthy N, Arumugasamy K, Anand U, et al. Effect of hemodialysis on circulating cystatin c levels in patients with end stage renal disease. Indian J Clin Biochem 2010; 25:43–6.
FLA 5.2.0 DTD TRSL786_proof 4 June 2014 8:52 pm ce
807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860