Assessment and Monitoring of Renal Proximal Tubular Tolerance of Nucleoside and Nucleotide Analogues Using Early Screening Tools in Patients Chronically Mono-infected With Hepatitis B Virus

Nucleotide analogues are associated in the long term with a risk of proximal tubular nephropathy (PT) with loss of phosphate, and, when compensatory mechanisms are overwhelmed, with osteopenia or osteoporosis. This toxicity has been particularly documented for tenofovir (TDF) in HIV disease, but its prevalence varies widely in the literature and is mainly associated with comorbidities: on average this prevalence is 0.39% after 48 weeks with exceptional cases of Fanconi syndrome described. In HBV monoinfection after 60 months of treatment with TDF, an 11% decrease of creatinine clearance (CreatCl) is observed. A single study showed a significant increase in creatinine level with entecavir (ETV) therapy, a second-generation nucleoside, hitherto not described as nephrotoxic. Furthermore, if the direct renal toxic effect characteristic of HIV in the kidney is well known, the role of HBV is less clear. Thus, HBV treatment appears to have a renal protective effect. The monitoring tools recommended by the SPC, CreatCl and plasma phosphorus level are late markers of tubular damage. The threshold of phosphate tubular reabsorption (TmPi/GFR) and the fractional excretion of uric acid (FEUA) are unexpensive early screening tools. However, the long-term evolution of this subclinical tubular involvement in HBV monoinfection is not known.