Comparison of Renal Function Between Tenofovir Disoproxil Fumarate and Other Nucleos(t)ide Reverse Transcriptase Inhibitors in Patients With Hepatitis B Virus Infection
Background: Nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs) have become a standard treatment for both HIV and hepatitis B virus (HBV) infections. Tenofovir disoproxil fumarate (TDF) has been associated with kidney injury and possible long-term damage in patients with HIV. Few studies have examined whether this holds true for patients treated for HBV.
Methods: Data were gathered from the Veterans Health Administration Corporate Data Warehouse between July 1, 2005 and July 31, 2015. Patients aged ≥ 18 years with HBV infection and prescribed a NRTI for > 1 month were included in the study and followed for 36 months. Patients with HIV infection were excluded, and patients treated with combination TDF/emtricitabine were analyzed separately from patients receiving only TDF. A linear mixed model was used to examine the effects of time and specific agent on renal function, which was measured with estimated glomerular filtration rate (eGFR) at various time intervals.
Results: There were 413 incidences of NRTI use in 308 subjects during the 10 years of the study with 39 cases of TDF use. There was a significant fixed effect of time, with eGFR reduction of 4.6 mL/min ( P < .001) over the course of the study for the full cohort, but the effects of each medication were not significant.
Conclusions: This multicenter, retrospective study did not demonstrate an association between TDF use and a greater degree of kidney injury compared with other NRTIs in patients with HBV, but further studies are warranted.
Discussion
This study demonstrated a decline in eGFR over time in a similar fashion for all NRTIs used in patients treated for HBV monoinfection, but no greater decline in renal function was found with use of TDF vs other NRTIs. A statistically significant decline in eGFR of −4.55 mL/min over the 36-month time frame of the study was demonstrated for the full cohort, but no statistically significant change in eGFR was found for any individual NRTI after accounting for the fixed effect of time. If TDF is not associated with additional risk of nephrotoxicity compared with other NRTIs, this could have important implications for treatment when considering the evidence that tenofovir-based treatment seems to be more effective than other medications for suppressing viral load.13
This result runs contrary to data in patients given NRTIs for HIV infection as well as a more recent cohort study in chronic HBV infectioin, which showed a statistically significant difference in kidney dysfunction between TDF and entecavir (-15.73 vs -5.96 mL/min/m2, P < .001).5-7,21 Possible mechanism for differences in response between HIV and HBV patients has not been elucidated, but the inherent risk of developing chronic kidney disease from HIV disease may play a role.22 The possibility remains that all NRTIs cause a degree of kidney impairment in patients treated for chronic HBV infection as evidenced by the statistically significant fixed effect for time in the present study. The cause of this effect is unknown but may be independently related to HBV infection or may be specific to NRTI therapy. No control group of patients not receiving NRTI therapy was included in this study, so conclusions cannot be drawn regarding whether all NRTIs are associated with decline in renal function in chronic HBV infection.
Limitations
Although this study did not detect a difference in change in eGFR between TDF and other NRTI treatments, it is possible that the length of data collection was not adequate to account for possible kidney injury from TDF. A study assessing renal tubular dysfunction in patients receiving adefovir or TDF showed a mean onset of dysfunction of 49 months.15 It is possible that participants in this study would go on to develop renal dysfunction in the future. This potential also was observed in a more recent retrospective cohort study in chronic HBV infection, which showed the greatest degree of decline in kidney function between 36 and 48 months (−11.87 to −15.73 mL/min/m2 for the TDF group).21
The retrospective design created additional limitations. We attempted to account for some by using a matched cohort for the entecavir group, and there was no statistically significant difference between the groups in baseline characteristics. In HIV patients, a 10-year follow-up study continued to show decline in eGFR throughout the study, though the greatest degree of reduction occurred in the first year of the study.10 The higher baseline eGFR of the TDF recipients, 77.7 mL/min for the TDF alone group and 89.7 mL/min for the TDF/emtricitabine group vs 72.2 to 76.3 mL/min in the other NRTI groups, suggests high potential for selection bias. Some health care providers were likely to avoid TDF in patients with lower eGFR due to the data suggesting nephrotoxicity in other populations. Another limitation is that the reason for the missing laboratory values could not be determined. The TDF group had the greatest disparity in SCr data availability at baseline vs 36 months, with 39.5% concurrence with TDF alone compared with 50.0 to 63.6% in the other groups. Other treatment received outside the VHA system also could have influenced results.
Conclusions
This retrospective, multicenter, cohort study did not find a difference between TDF and other NRTIs for changes in renal function over time in patients with HBV infection without HIV. There was a fixed effect for time, ie, all NRTI groups showed some decline in renal function over time (−4.6 mL/min), but the effects were similar across groups. The results appear contrary to studies with comorbid HIV showing a decline in renal function with TDF, but present studies in HBV monotherapy have mixed results.
Further studies are needed to validate these results, as this and previous studies have several limitations. If these results are confirmed, a possible mechanism for these differences between patients with and without HIV should be examined. In addition, a study looking specifically at incidence of acute kidney injury rather than overall decline in renal function would add important data. If the results of this study are confirmed, there could be clinical implications in choice of agent with treatment of HBV monoinfection. This would add to the overall armament of medications available for chronic HBV infection and could create cost savings in certain situations if providers feel more comfortable continuing to use TDF instead of switching to the more expensive TAF.
Acknowledgments
Funding for this study was provided by the Veterans Health Administration.
