Kidney and beyond - Review Article

Measurement Error in Estimated GFR Slopes across Transplant Chronic Kidney Disease Stages
Mohammad Akhtar Hossain, Ahmad Attia, Ahmed Shoker

Saskatchewan Transplant Program, St. Paul's Hospital, Saskatoon, Sask., Canada

Address of Corresponding Author

Am J Nephrol 2010;31:151-159 (DOI: 10.1159/000259902)

  Key Words

• Cockcroft-Gault
• Modified diet in renal disease
• Glomerular filtration rate

  Abstract

Background: This study examines if transplant glomerular filtration rate (GFR) slope prediction is affected by the degree of transplant chronic kidney disease (CKDT) stage. Methods: Serial changes in estimated GFR (eGFR) by Cockcroft-Gault (CG) and Modified Diet in Renal Disease-Isotope Dilution Mass Spectrometry (MDRD-IDMS) equations were compared to simultaneous changes in isotope GFR (iGFR) in renal transplant patients who had at least four scans. Results: Total number of patients (iGFR scans) was 99 (772) while the corresponding numbers in CKDT stages 1-4 were 33 (103), 69 (239), 75 (316) and 37 (96), respectively. Measurement error [(eGFR - iGFR) × 100/iGFR] (median ± IQR, interquartile range) estimated from CG and MDRD-IDMS slopes were -414.29 ± 276.16% and -342.86 ± 210.18% (stage 1); -350.00 ± 301.22% and -300.00 ± 525.00% (stage 2); -26.02 ± 404.38% and -26.58 ± 423.13% (stage 3); 10.26 ± 142.18% and -76.92 ± 145.64% (stage 4), respectively. The proportion of patients with CG measurement error 1-fold in stages 1 and 2 of 12 and 14.5% was significantly (p < 0.05) lower than that of 36.3 and 52.8% at stages 3 and 4, respectively. Similar measurement errors were observed for MDRD-IDMS. Conclusions: Transplant GFR slope prediction is affected by the degree of renal dysfunction. Errors in slope prediction are much higher in those with better function and thus add another limitation for eGFR use in longitudinal studies on progressive graft dysfunction.

Copyright © 2009 S. Karger AG, Basel

  Author Contacts

Dr. Ahmed Shoker, MD, FRCP (C)
Department of Medicine, Division of Nephrology, University of Saskatchewan
103 Hospital Drive
Saskatoon, SK S7N 0W8 (Canada)
Tel. +1 306 966 2630, Fax +1 306 966 7996, E-Mail ass787@mail.usask.ca

  Article Information

Received: July 9, 2009
Accepted: October 9, 2009
Published online: November 18, 2009
Number of Print Pages : 9
Number of Figures : 3, Number of Tables : 3, Number of References : 28