The potential effect of using the Cockcroft-Gault method on tenofovir-associated renal impairment reports and on clinical decisions regarding tenofovir use in individual patients: implications for the future

Introduction: In Namibia, the Cockcroft-Gault (C-G) method is recommended for monitoring renal function in HIV patients receiving tenofovir disoproxil fumarate (TDF)-containing combination antiretroviral therapy (cART). However, there are concerns with the potential over-reporting of TDF-associated renal impairment. Methods: Retrospective study comparing the renal function of patients receiving 2nd line cART with either C-G or Chronic Kidney Disease-Epidemiology (CKD-EPI) methods. Results: 71 patients were included. The majority (62%) received TDF-containing 1st line ART. All received 2nd-line cART containing TDF/ lamivudine (3TC)/ zidovudine (AZT) and LPV/r. Before switching to 2nd-line cART, 40.8% and 8.5% had abnormal eGFR according to C-G and CKD-EPI methods respectively. During 2nd-line cART, 47.9% and 7% of patients had abnormal eGFR by C-G and CKD-EPI methods, respectively, and 4.1% and 2.8% respectively experienced a decline in eGFR. There was a significant lack of agreement between the two methods. Conclusion: The C-G method has the potential to report more cases of TDF-associated renal impairment. Consequently, national guidelines in Namibia and other pertinent countries should be reviewed if this is the recommended method for monitoring renal function.