Letter: chronic kidney disease risk in patients with chronic hepatitis B

We read with interest the paper by Wong et al about the risk of chronic kidney disease (CKD) progression in patients with chronic hepatitis B.1 In that study, patients receiving tenofovir disoproxil fumarate (TDF) were at a slightly increased risk, while those treated with entecavir had a nearly equal risk as untreated patients.

However, we still have some concerns about the study. First, in addition to the chosen CKD Epidemiology Collaboration (CKD-EPI) equation, Cockroft-Gault formula and MDRD-4 (Modification of Diet in Renal Disease Study) formula were two others assessing estimated glomerular filtration rate (eGFR). However, choice of different formulas influenced the epidemiology of CKD, which might lead to different conclusions.2 Also, the CKD-EPI formula had greater bias in people with diabetes compared to those without diabetes, especially in those with normal renal function.3

Second, although hepatitis B virus (HBV) markers were sequentially collected in the study, only the baseline parameters were given in the article. Since patients’ response to different drugs could be evaluated by the change in HBV DNA burden, the prognosis of those who do not clear HBsAg with therapy is unsatisfactory.4 Progression of hepatitis B disease requires longitudinal measurement of HBV DNA. Could progressive CKD be related to higher levels of HBV DNA in a subgroup of patients who did not fully suppress HBV replication?

Wong's study answered some questions, but did not totally exclude the potential risk of reduced kidney function in some patients, which still requires more data from clinical studies enrolling more participants with longer follow-up.