Long-Term Treatment with Tenofovir in Asian-American Chronic Hepatitis B Patients Is Associated with Abnormal Renal Phosphate Handling

Background Increased risk of defective urinary phosphate reabsorption and osteoporosis has been reported in HIV and chronic hepatitis B (CHB) patients treated with tenofovir disoproxil fumarate (TDF). Aims Goals of this study were to evaluate the prevalence of renal phosphate wasting and abnormal bone mineral density in CHB patients taking TDF compared to CHB patients treated with entecavir (ETV) and untreated CHB patients. Methods This is a cross-sectional study of 146 consecutive Asian-American CHB patients who were treatment naïve ( n = 60) or treated with either TDF ( n = 42) or ETV ( n = 44). Proximal tubular handling of phosphate was assessed by the maximal rate of tubular reabsorption of phosphate (TmPO 4 ) divided by glomerular filtration rate (GFR) (TmPO 4/ GFR). Bone mineral density (BMD) was measured using dual X-ray absorptiometry. Results TmPO 4/ GFR was similar among CHB patients treated with TDF compared to untreated patients and patients taking ETV. However, among patients treated with ≥18 months of TDF or ETV, prevalence of abnormal TmPO 4/ GFR was higher among patients treated with TDF compared to ETV (48.5 % (16/33) vs. 12.5 % (3/24), p = 0.005). Overall prevalence of osteoporosis in this cohort of CHB patients was 14 %, with no significant difference between the three groups. Renal phosphate handling did not correlate with osteoporosis. Conclusions Chronic hepatitis B patients treated with ≥18 months of TDF experienced an increased risk of proximal tubular dysfunction. TDF did not increase the risk of osteoporosis. Longitudinal studies are needed to confirm these findings.