Establishment of an assay for pharmacodynamic monitoring of mycophenolic acid

39TH ANNUAL

41

CONFERENCE

OF THE CANADIAN

LEAD TOXICrrY - DISCOURAGING USE OF ZPP (ZINC PROTOPORPHYRIN) FOR DETECTION

43

SOCIETY OF CLINICAL CHEMISTS

ESTABLISHMENT OF PHARMACODYNAMIC

AN ASSAY FOR MONITORING OF

Scott~ ~E.. and Morrell, J., Metro Health Services Trace Element Laboratory, Department of Laboratory Medicine, Division of Clinical Biochemistry, Saint John Regional Hospital, Saint John, New Brunswick E2L 4L2, Canada

MYCOPHENOLIC ACID Lanmnan. L.J.. LeOatt, D.F., and Yatscoff, R.W., Dept of Labomtory Medicine and Pathology, University of Alberta, Edmonton, Alberta, T60 2B7, Canada

Objeetiv~ Cum~tiy both blood lead and ZPP values are re.qu~t~ when evaluating patients for lead toxicity. To challenge this the utilityof ZPP to detect lead intoxication in our own city population was evaluated, retrospectively, using available test data for blood lead and ZPP from 1,255 residents. Methods Whole blood lead analysis was performed using flsmelessatomic absorption spectroscopy (AAS) usin 8 a model Z8200 Zeeman AAS (Hitachi, N i m i Sangyo, Rexdale, Ont., Canada.) ZPP analyms was performed usin8 a Protofluor-Z hematofluorumeter (Helena Laboratories, Beaumont, "IX, USA.) In accordan~ with the Working Group on Lead Intervention Levels and Strategies, Health and Welfare Canada (September 1994), our referenoe value for blood lead is <0.48 I~mol/L (< 10 tts/dL.) For ZPP our reference value is <70 panol/mol hacm. The diagnostic utilityof ZPP was evaluated using these values. Results Data were separated into 3 8roupa; children 0 - 16y, females > 16y, and males > 16y. Sensitivity and specificity data were:

Objective The pharmacodynamic monitoring of the biological effect of immunosuppressive drugs provides an alternative to traditional therapentic drug monitoring. We chose to inveslisate this using Mymphemlie Acid (M/A), an immunesuppressive drug which mediates its effect by inhibition of inosine monophosphate dehydrogonase (IMPDI-I), a key enzyme in the de novo hiosynthesis of pminea. Methods & Results Using an assay developed for m¢=unmm~nt of IMPDH activity in whole blood (WB), the enncenttation of MPA required for 50% inhibition of enzyme a~ivity was in the range of 2.0-5.0 n~/L for both human and rabbit blood, while that for the major mctabolite MPA 81ucuronide was > I00 mg/L. The levelof enzyme activity in WB was found to be dependent on the concentration of the white blood cells end was not affected by the typo of anticmsuhmt used and was stable in WB specimens stored for up to 72 hours at 4°C. Conclusion The assay described here provides the bern for the evalualion of a pharmacodynamic approach for monitoring MPA in both sninud and clinical studies.

0-16 y

Males >16 y

Females > 16 y

Total

185

489

581

Sensitivity

0.50

0.12

0.30

Specificity

0.93

0.95

0.92

Conclusions ZIP is unsuitable as diasnostic tool for lead toxicity, defined as a blood lead level >I-OA8 p,mollL. These findings are consistent with Leun8 et al. (Clin Biochem 1993;26:491 - 6), the Centers for DL_~_~ Control (CDC), and othen. These data will be used in an education program for physi~ms, enoouraging relianoe on blood lead results and discouraging requests for ZIP except, perhaps, for occupational exposure.

42

METHANOL: EXPERIENCE IN ]PREDICTING LENGTHS OF H E M O D I A L Y S I S T H E R A P Y LeGatt. D.F. Dept Lab Medicine and Pathology, U of A Hospitsi, Edmonton, Alberta, T60 2137, Canada

Objective To evaluate the clinical utility of a treatment table formulated to predict lengths of hemudialysis (HI)) therapy required to decrease [MeOH] to 6 mmol/L by assessing its applicability in 36 subsequent eases of lvieOH poisonin8. Method~ For each patient undc~goin8 HI), a serum MeOH level was determined <0.5 h prior to or early during HD and a HD time was sule~ed from the treatment table. At the end of this period, another MeOH was determined and the actual decrease in [MeOH] was compared to the

expected decrease. Rl~u/ts The expoetod and actual deeresses in [MeOH] ranged from 2 to 119 mmol/L with 89% of the actual decreases deviatin8 by 5 mmol/L. Conch~>n A HI) treatment table for MeOH has been clinically useful in Imuing such poisonings.

334

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E V A L U A T I O N OF THE DADE I N T E R N A T I O N A L P A R A M A X T H E O P H Y L L I N E ASSAY Wesenbem. J.C. and Creuey, L., Clinical Laboratory, Red Deer Resional Hospital, P.O. Bag 5030, Red Deer, Alberta, T4N 6R2, Canada

The Paramax theophylline (THEO) assay, based on the Syva EMIT tnothodelogy, uses a single reagent tablet for quantitative serum or plasma T H E O determination. Objecliws To evaluate the assay:, switchin8 from Abbott T D X to Pemmax would enhance woAflow. Methods After calibration, to assess impracimon, 3 Dada T D M and IAC controls were run in triplicate twice per day on 20 days. For eonelation, 108 patient sera with THEO Sl~Umingthe assay range (14 - 27.21~mol/L) were mn in duplicate on the Parsmax and TDx. To sss~s in~'mence, 9 lipemic, 8 ieteric and 8 bemoly2~ sent were included. Also, 14 sera with no T H E O were rua Calibra~ were run pe~zlicellyto asseu the 30-dey calibrationstabilityclaim. Results Imprecision results were satisfactory: TDM1 ' r D l ~ Mean

TDM3 IACI IAC2 IAC3

26.2

75.9

151.1

26.1

79.1

142

3.4

2.4

3.3

3.2

2.6

3.2

(cv~)

3.5

3.4

4.3

3.2

3.2

4.5

Total (CV%)

4.9

4.2

5.4

4.5

4.1

5.5

(umol/L) Within-run

(cv~) Betweon=ron

Correlation was excellent (Paramax - 0.97 TDx + 0.64; r - 0.994) and not significantly affected by lipomla, ieterus or hemolysis. All results

CLINICAL BIOCHEMISTRY, VOLUME 28, J U N E 1995

P O S T E R ABSTRACTS were zero for theophylline-nesItive sere. Some decline in the racovery of the mid and hish calibraton ¢54 and 222 nunol/L) was seen. 1 ~ (%) at 21, 31 and 40 days post-calibrationwas 95, 93, 96 and 90, 86, 84, respceevely. The zero e,alibratof'wes uncaanlted. Condu~ona Paramax T H E O aumy offers satisfactoryperformance and will enhance laboratory wmktlow.

45

MECONIUM TESTING: A RELIABLE WAY TO DETECT INTRAUTERINE COCAINE OR OPIATE EXPOSURE Halstead. A.C.. Kennedy, K., Williams, K.P., Ling, E., and Albemheim, S.G., Depts. of Pathology, Obstetrics and Pediatrics, University of British Columbia, Vancouver, B.C., Canada.

Detection of drug use durin8 prestmney is important for care of mother and newborn. Meconium testing may be better than matenud history and urine drug screening for identi~..~ingintrauterine drug expoeure, but not all methoda perform well. Objective To evaluate mdioimmunoasesy (RIA) screening for morphine and benzoyle~onine (BE) in mceonium. MethodJ Meoonium was enllcetcd daily from newborns of 58 consentin8 mothers. Durin8 pregnancy 12 m,ed cocaine, 2 heroin, 10 be(h, and 34 neither drug. An acetonitrile e ~ t c t of meconinm was tested by RIA (Coat-A.Connt Cocaine Metabofite and Senun Morphine kits, Diasnestie Products Corp) using spiked meeonium (BE or morphine) for stsndards.Resultswere eompan:d to zeporteddrug use and urinedrag sereens (enzyme immunoassay (Syva EMIT I~ and thin layer chromatography (Toxilab)) documented in patient records. Re.ml~ BE measured <35 tts/L and morphine <1 p~/L in drug-frac meennium. In the 22 cocaine-expmed neonates, BE was pesitlve in 18 meenniums, compared to 2/7 neonatsJ and 4/7 matenud urines. One case reporting heroin use only had BE in memninm. The 4 false negatives were due to cocaine use before 19 weeks gestation. Murphine was positive in meconimn from 8/12 heroin-exposed newborna Negatives were due to first trimester heroin tug. Use at 16-18 weeks gave a borderline result (2 ttg/L). Heroin was nut confu~cd in urine. Conclmton This RIA me~od is an effcefive screen for cocaine or heroin exposure in the last half of pregnancy and is clearly better than traditional urine drug screening in this population. 46

MECONIUM PREPARATION FOR SCREENING FOR COCAINE, OPIATES AND CANNABINOIDS BY RIA Kennedv. K.. and Halstead, A.C., Dept. of Pathology, Univer~ty of British Columbia and B.C.'s Children's Hospital, Vancouver, B.C., V6H 3V4, Canada

Mcconium is said to be better ghan urine drug screening and maternal history for detecting intrauterine exposure to illicit drugs, but methods vary in sample preparation, immuncassay screens used and cut-off cow centrations. O b j ~ w To compare various es~racfion techniques for preparing mceonium for cocaine metabolite (BE), opiate and cannabinoid screening by radioimmunoassay. Method8 Drus-frue meconium ssmples (0.5 g) mixed with 0.2-0.5 mL iodinated tracer (benzoylecgonine, morphine or tetra-hydrocaunabinoie acid) were extracted with 2-3 mL acetone, methanol or acetonitrile. Extracts were counted directly and after drying and reconstituting with phosphate buffer. Ease of extraction and tracer recovery (eonceted for dilution) were compared. Maximum bindin8 of meconium extracts in the

CLINICAL BIOCHEMISTRY, "VOLUME 28, JUNE 1995

RIA (Coat-A-Connt, Dingnmtle PmdueU Cow.) w u ,do m m ~ L Rein/t, Methanel mixed well with maconinm but the extractwas elcody. Acetonittileand acetone extractswere elcarand ~Ixtrated ready from a solid phase. Extraea in solvent gave lower counts than throe in buffer. Reeoveries (in buffery. methanol

xeetone

CH3CN

BE

95%

98%

109%

MoEphine

85%

96%

94%

Cmmabinoid

63%

70%

61%

Maximum binding of maconium extracts was poor (4-8%) in the eanmbinoid assay, similar to urine (40%) in the BE amay, and about 75% of urine values in the opiate assay (45%). Conclusion ~ or acetone extractions are preferred because of eme o f ~ None of the ex~c~iom wac mitsble f o r ~ in this RIA.

47

CLINICAL EVALUATION O F T H E i-STAT ANALYTZR Meek. T.. Cmilla, L., ~ B. and Yatacoff,R.W., Dept of Laboratmy Medicine & Pathology and Dept of Emergency Medicine, Univeraity of Alberta Hospital& Edmonton, Alberta, T6O 2B7, Canada.

Object/w To asseu the effects of the uac of the i~TAT analyz~ un setect pati~t outcont~ in tbe emc~ency ¢l¢~Jtn~nt Me~ods Two i-STATmdyzen with e s m l d ~ eapeble of mcaant~ acd i m , potsuium, chloride, urea, glucose and hemataedt were placed in the Emetseney Depertment OH)) at the Univenity of Alberta Hoq~tsla Selection of patients was based on axe testing required. All tracking of events was performed by an experienced ED nurse. Control dats'were eollacted from l~ients with simihr trot profiles but who~ t e ~ were ena. lyzed by the central laboratory. Resul~r In our ongoing study we have found that the use of the i-STAT significantly reduced (245 rain for control vs 140 rain for i-STAT) the time to dischurga from the initial assessment by the physician (p
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