Background: Cystatin C has been proposed as an alternative marker of kidney function among HIV-infected persons in whom serum creatinine is affected by extrarenal factors.
Methods: In this cross-sectional study, we compared estimated glomerular filtration rates (eGFR) using serum creatinine versus cystatin C between 150 HIV-uninfected and 783 HIV-infected men. We evaluated the prevalence of chronic kidney disease (CKD; eGFR less than 60 mL/min/1.73 m2) and examined the influence of extrarenal factors on GFR estimates among HIV-infected men.
Results: Estimated GFRSCR was similar by HIV serostatus, but eGFRCYSC was lower in HIV-infected men. A higher proportion of HIV-infected men were classified as having CKD when using eGFRCYSC versus eGFRSCR (7% vs 5%, P < 0.01). In HIV-infected individuals without CKD, eGFRSCR was higher than eGFRCYSC, whereas it was lower than eGFRCYSC in persons with CKD. In HIV-infected men, older age, proteinuria, and prior clinical AIDS were inversely associated with both GFR estimates. Higher serum albumin levels and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker use were associated with lower eGFRSCR. HIV viral load, hepatitis C coinfection, and serum alkaline phosphatase were inversely associated with eGFRCYSC.
Conclusion: Among HIV-uninfected and HIV-infected men of similar social risk behaviors, GFR estimates differed by biomarker and kidney function level. Estimated GFRCYSC classified a larger proportion of HIV-infected men with CKD compared with eGFRSCR. Differences between these GFR-estimating methods may be the result of the effects of extrarenal factors on serum creatinine and cystatin C. Until GFR-estimating equations are validated among HIV-infected individuals, current GFR estimates based on these biomarkers should be interpreted with care in this patient population.