Comparison of glomerular filtration rate estimates vs. 24-h creatinine clearance in HIV-positive patients

Background: Guidelines for kidney function monitoring and antiretroviral drug dosing are available and respectively refer to glomerular filtration rate and creatinine clearance (CrCl). Objective: The aim of the study was to compare kidney function estimates vs. measured 24-h CrCl in HIV-infected subjects. Methods: A cross-sectional design was used, with comparison of Cockcroft-Gault (CG), original and simplified modification of diet in renal disease (MDRD) equations vs. measured 24-h CrCl. Subjects were HIV-infected, 18-70 years old, without pre-existing kidney disease. Results: Results are presented as mean (± standard deviation), unless otherwise stated. The study population consisted of 90 patients, of whom 71% were male, with a mean age of 45 years (± 6.5 years). At the time of evaluation, the mean body mass index was 23 (± 3.3); mean serum creatinine was 0.91 mg/dL (± 0.2 mg/dL); and mean blood urea nitrogen (BUN) was 34.7 mg/dL (± 10.6 mg/dL). Differences between paired methods were all significant (P <0.00001), except between CG and simplified MDRD (P = 0.21; Pearson r = 0.81). In univariate analysis, male gender, CD4 nadir, hepatitis B virus coinfection, BUN and current CD4 cell count showed a significant positive correlation (P <0.2) with the difference between measured 24-h CrCl and either CG or simplified MDRD estimates. In multivariate analysis, only BUN showed a significant positive correlation (P <0.05). Conclusions: Estimates were lower than the measurements of 24-h CrCl. Original MDRD estimates were lower than those with other equations. CG and simplified MDRD estimates showed a satisfactory correlation.