Purpose: Estimated glomerular filtration rate (eGFR) decline in HIV-1-infected patients exposure to tenofovir disoproxil fumarate (TDF) has been widely assessed using linear models, but nonlinear assumption is not well validated. We constructed a retrospective cohort study to assess whether eGFR decline follows nonlinearity during antiviral therapy.
Patients and Methods: We examined 823 (299 of TDF users and 524 of non-TDF users) treatment-naïve HIV-1-infected participants (age ≥  17 years, initial eGFR ≥ 90 mL/min/1.73m²). Estimated GFR trajectories were compared by one-linear and piecewise-linear mixed effects models, before and after propensity score matching, respectively. Whether the incidence of renal dysfunction (reduced renal function [RRF], eGFR < 90 mL/min/1.73 m² and rapid kidney function decline [RKFD], eGFR > − 3 mL/min/1.73 m²/year) follows nonlinearity was assessed by logistic regression.
Results: The median follow-up time of this study was 10 (interquartile range, 2– 20) months, during which 178 (21.6%) experienced RRF, and 451 (54.8%) experienced RKFD. The slopes (mL/min/1.73 m²/year) of eGFR were − 5.31 (95% CI: − 6.57, − 4.06) before 1.40 years, 4.83 (95% CI: 1.38, 8.28) from years 1.40 to 2.30 and − 3.71 (95% CI: − 5.97, − 1.45) after 2.30 years among TDF users. Within years 1.40– 2.30, each year of TDF exposure was associated with a 78% decreased risk of RKFD (95% CI: − 91%, − 49%). In comparison, eGFR increased slightly at the initiation of antiviral therapy, declined after 2.15 years (− 4.96; 95% CI: − 5.76, − 4.17) among non-TDF users. Such a progression nonlinear trajectory was missed on the assumption of one-linearity, whether in TDF or non-TDF users.
Conclusion: Over the piecewise mixed-effects analyses with the advantage of revealing the true nature of the exposure outcome relationships, an interesting reverse S-shaped relationship was observed. A routine screen based on nonlinearity could be more helpful for patient management.
Keywords: nonlinear trajectory, renal function, human immunodeficiency virus-1