Erratum Regarding “Phosphate Removal With Several Thrice-Weekly Dialysis Methods in Overweight Hemodialysis Patients” [Am J Kidney Dis 2009; 54:1108-1115]

Erratum Regarding “Phosphate Removal With Several Thrice-Weekly Dialysis Methods in Overweight Hemodialysis Patients” [Am J Kidney Dis 2009; 54:1108-1115] The article entitled “Phosphate Removal With Several Thrice-Weekly Dialysis Methods in Overweight Hemodialysis Patients” (Tonelli et al, American Journal of Kidney Diseases 2009;54(6):1108-1115) underreported the calculated dialyzer phosphorus clearance due to an error in the adjustment of the average intradialysis serum phosphorus level to plasma water concentration. The error was due to a typographical error in a formula in Katopodis et al (reference 22 in the article in question), which was used to adjust plasma water correction based on the serum total protein concentration. Katopodis et al specified the adjustment factor as having units of grams per liter, whereas the units should have been grams per deciliter. This led to an overestimation of the mean intradialytic plasma water concentration when the formula was applied as written, which in turn caused an underestimation of clearance when this quantity was divided into the total amount of phosphorus recovered. The conclusions of the article remain unchanged; however, the calculated dialyzer clearance values need to be corrected as follows: 1. In the abstract, the sentence “The double-dialyzer strategy also was associated with greater phosphate clearance (113.4 mL/min; 95% confidence interval [CI], 101.4 to 125.3) than the other 3 strategies (83.9 mL/min; 95% CI, 71.6 to 96.2; 86.6 mL/min; 95% CI, 73.8 to 99.3; and 83.0 mL/min; 95% CI, 71.1 to 94.9), but not greater phosphate removal” should read “The double-dialyzer strategy also was associated with greater phosphate clearance (177.2 mL/min; 95% confidence interval [CI], 158.6 to 195.9) than the other 3 strategies (129.8 mL/min; 95% CI, 111.2 to 148.4; 135.4 mL/min; 95% CI, 115.4 to 155.3; and 131.2 mL/min; 95% CI, 112.0 to 150.4), but not greater phosphate removal.” 2. Figure 3, which shows dialyzer clearances, should be replaced by the version displayed in this correction. 3. Table 3, which lists dialyzer clearances, should be replaced by the version shown in this correction. The other data in the article (regarding dialysate phosphorus recovery and changes in serum phosphorus concentrations with the different schedules employed) were not affected by this error; as stated previously, the conclusions are not altered by these corrections. The authors thank Dr John Daugirdas for pointing out this error.

Figure 3. Effect of dialysis modality (Time [4.5-hour dialysis], Std [4-hour dialysis ⫹ 0.5-hour ultrafiltration], Flow [4-hour dialysis at increased dialysate flow], and DD [4-hour dialysis using double dialyzer]) on phosphate clearance and phosphate removal. Values expressed as mean ⫾ SE. All comparisons are adjusted for rolling baseline serum phosphate level. Conversion factor for serum phosphate in mg/dL to mmol/L, ⫻0.3229. Am J Kidney Dis. 2012;59(5):743-744

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Erratum Table 3. Phosphate Clearance and Phosphate Removal by Dialytic Regimen Characteristic

Phosphate Clearance (mL/min)

Phosphate Removal (mg)

Standard hemodialysis Increased dialysis time Increased dialysate flow 2 dialyzers in parallel

129.8 (111.2-148.4) 135.4 (115.4-155.3) 131.2 (112.0-150.4) 177.2 (158.6-195.9)

1,395.8 (1,163.6-1,628.1) 1,435.7 (1,179.9-1,691.5) 1,371.4 (1,132.0-1,610.7) 1,487.8 (1,248.6-1,727.1)

Note: N ⫽ 18. Values expressed as mean (95% confidence interval). Adjusted for rolling baseline serum phosphate level. Serum phosphate expressed in mg/dL; conversion factor for mmol/L, ⫻0.3229.

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Am J Kidney Dis. 2012;59(5):743-744