Value of Cystatin C-Based e-GFR Measurements to Predict Long-Term Tenofovir Nephrotoxicity in Patients With Hepatitis B.

Background: Cystatin C is a genuine marker for detecting minor reductions in estimated glomerular filtration rate (e-GFR).

Study Question: We aimed to investigate the efficiency of cystatin C levels in predicting nephrotoxicity due to antiviral therapy in patients with chronic hepatitis B virus infection.

Study Design: Seventy-six naive hepatitis B virus patients and 44 controls were enrolled in this prospective cohort study.

Measures And Outcomes: Serum cystatin C, phosphate and creatinine levels, and urinary albumin/creatinine ratios of all patients were measured at baseline, 3rd, 12th, and 24th months. Nephrotoxicity was determined according to the amount of change in creatinine level at the fourth year of treatment compared with baseline ([INCREMENT]Cr0-4).

Results: Mean age was 36.1 ± 9.2 years and 40 (52.2%) of patients were women. There was no significant difference between baseline values of tenofovir disoproxil fumarate and entecavir groups. Although the creatinine level at the fourth year of treatment was statistically nonsignificant compared with baseline in the entecavir group, it was significantly higher in the fourth year of tenofovir treatment compared with baseline (0.95 ± 0.27 mg/dL vs. 0.76 ± 0.16 mg/dL, P = 0.002). While the increase in [INCREMENT]Cr0-4 was ≥0.2 mg/dL in 43.2% of patients in the tenofovir group, this rate was 18.8% in the entecavir group. Diagnostic accuracy in identifying decreased renal function as area under the curve (AUC) was high for baseline serum cystatin C level; furthermore, the highest AUC was calculated for cystatin C plus creatinine-based e-GFR equation (AUC: 0.81, P < 0.001).

Conclusions: Long-term tenofovir disoproxil fumarate nephrotoxicity can be predicted by serum cystatin C plus creatinine-based e-GFR measured before treatment.