Abstract
Background
Broad use of tenofovir and an ageing HIV-infected population have created an interest in renal function in HIV patients. Serum cystatin C is a newer marker of renal function and might be more sensitive than creatinine.
Methods
Patients were enrolled consecutively in an observational study. HIV-seropositive patients naive to antiretroviral therapy (n=261) were compared with healthy volunteers undergoing check-up procedures (n=193). Estimated glomerular filtration rate (eGFR) was derived using creatinine-based Modification of Diet in Renal Disease (MDRD) and Cockcroft–Gault formulas or cystatin C-based calculations. HIV-seropositive patients starting antiretroviral therapy (n=92) were followed prospectively after enrolment.
Results
MDRD showed a higher median eGFR in antiretroviral- naive HIV-seropositive patients compared with controls (104 versus 93 ml/min; P<0.001). Cockcroft–Gault gave similar results (118 versus 106 ml/min; P<0.001). By contrast, cystatin C levels in HIV-seropositive individuals were higher, resulting in a lower median eGFR compared with controls (99 versus 120 ml/min; P<0.001). Cystatin C was positively correlated with HIV RNA (r=0.33, P<0.01) and inversely correlated with CD4+ T-cell count (r=-0.29, P<0.01). Initiating antiretroviral therapy (n=92) decreased cystatin C levels and led to an increased cystatin C-based eGFR from median 84 to 103 ml/min at week 24 (P<0.001). Serum creatinine was not substantially altered.
Conclusions
Correlation of cystatin C with HIV RNA and CD4+ T–cell count, plus decrease of cystatin C after suppression of HIV replication, suggest an increase of cystatin C levels by active HIV infection. This might result in overestimation of renal impairment, particularly in treatment-naive patients. Therefore, use of cystatin C to calculate GFR in HIV-seropositive individuals should not be recommended without further validation.