Renal function change after switching tenofovir disoproxil fumarate for tenofovir alafenamide in the HIV-positive patients of a metropolitan sexual health service

Background: Tenofovir disoproxil fumarate (TDF) is widely used in the management of HIV-infection, but has been associated with renal impairment in a small proportion of patients. Tenofovir alafenamide (TAF), a novel prodrug of tenofovir, causes less renal impairment and can improve renal function in patients switched from TDF. The factors which predict improved renal function in patients switching from TDF to TAF have yet to be described. Aim: To determine which patient factors are associated with an improvement in renal function following the switch from a TDF- to a TAF-based HIV antiretroviral regimen. Methods: A retrospective analysis was performed of a cohort from a publicly funded sexual health clinic in Sydney, Australia. All HIV-positive clinic patients switched from a TDF- to TAF-containing regimen between January 2016 and August 2018 were eligible for inclusion. Laboratory results were obtained from patients' electronic medical records. The statistical significance of differences between pre- and post-switch means was determined by paired t-tests, adjusted for baseline values, and associations between continuous variables by univariate linear regression. Results: 79 patients met inclusion criteria. The majority were male (89%), with a median age of 44 years (IQR: 34.5 to 53). Patients had a mean pre-switch estimated glomerular filtration rate (eGFR) of 952 mL/min/1.73 m(2), and there was no significant change post-switch (p=0.062). Pre-switch eGFR was a significant predictor of the magnitude of eGFR change after the switch (p<0.001), but there was no significant association with age (p=0.189), cumulative TDF exposure (p=0.454) or baseline urinary protein to creatinine ratio (p=0.814). Conclusion: While there was no significant difference in mean eGFR, in patients switched from TDF to TAF, baseline eGFR was a significant predictor of the change in eGFR. This suggests that patients on TDF with poorer baseline renal function would benefit more from switching to TAF. Further study to explore this association is warranted.