Background: Tenofovir (TDF) can cause kidney injury through tubular dysfunction, with or without drop of estimated glomerular filtration rate (eGFR). Whether mild eGFR reductions during treatment should be considered a reason for prompt TDF discontinuation, however, remains unclear.
Methods: Patients with normal pre-TDF eGFR levels, who had developed mild renal impairment (i.e., two consecutive eGFR results between 89-60 ml/min) on TDF, were observed until onset of chronic kidney disease (CKD), defined as two eGFR<60 ml/min 3 to 6 months apart. Multivariable Poisson regression analysis was used to investigate whether outcome was associated with current and cumulative use of TDF (modeled as time-varying covariates).
Results: 2023 (29%) out of 6984 patients developed mild renal impairment on TDF. Among them, 191 progressed to CKD. The incidence of CKD did not significantly differ during TDF treatment (2.6 per 100 PYFU; 95%CI 2.2-3.2) or after its discontinuation (2.2 per 100 PYFU; 95%CI 1.8-2.6). However, the rate of CKD was significantly higher among patients continuing with TDF treatment compared to those who had discontinued it within 6 months of occurrence of mild renal impairment (aIRR 4, 95%CI 2.4-6.8). In contrast, among patients who had maintained TDF >6 months despite mild renal impairment, current TDF use was not associated with a significantly higher rate of CKD. Other significant predictors of CKD were older age, intravenous drug use, diabetes, hypertension, lower pre-TDF eGFR, higher eGFR drop since TDF introduction and longer exposure to TDF.
Conclusions: Prompt discontinuation of TDF among patients developing mild renal impairment may prevent further progression of renal damage.