Natural history of chronic hepatitis B in untreated adults without cirrhosis according to baseline hepatitis B virus DNA and alanine aminotransferase concentrations: a systematic review and meta-analysis.

[BACKGROUND] Chronic hepatitis B (CHB) affects an estimated 254 million people globally. Historically, WHO and professional society guidelines have recommended treatment for individuals at high risk of disease progression, including those with hepatitis B virus (HBV) DNA concentrations >20 000 IU/mL. Whether individuals at lower risk, including those with HBV DNA <20 000 IU/mL and normal alanine aminotransferase concentrations, benefit from treatment remains uncertain. To inform 2024 WHO guidelines and the potential expansion of treatment threshold recommendations, we conducted two linked systematic reviews and meta-analyses; this analysis examines the incidence of clinical outcomes in untreated adults with non-cirrhotic CHB stratified by baseline HBV DNA and ALT concentrations.

[METHODS] In this systematic review and meta-analysis, we searched PubMed, Embase, Web of Science, and the Cochrane Library for longitudinal prospective and retrospective cohort studies, randomised controlled trials, and non-randomised studies of interventions, published in any language, from Jan 1, 2000, to Feb 6, 2023. We also reviewed the reference lists of included studies and systematic reviews and consulted networks of experts to identify other data sources. Included studies followed up adults (≥18 years) with non-cirrhotic CHB who had no history of antiviral therapy at enrolment, had baseline HBV DNA quantification and ALT measurement, had a follow-up period of at least 48 weeks, and assessed one or more of six key clinical outcomes (hepatocellular carcinoma, cirrhosis, liver-related mortality, all-cause mortality, liver decompensation, and indication for liver transplantation) or six additional outcomes (advanced liver fibrosis, progression of liver fibrosis, becoming eligible for antiviral treatment, hepatitis flare, and HBsAg and HBeAg seroclearance). Outcomes were required to be stratified by HBV DNA concentrations (<200 IU/mL, <2000 IU/mL, 2000-19 999 IU/mL, 20 000-199 999 IU/mL, and ≥200 000 IU/mL) or ALT concentrations (less than the upper limit of normal [ULN], 1·0-1·9 × ULN, and ≥2·0 × ULN). We excluded studies that focused solely on individuals who were pregnant; were co-infected with HIV, hepatitis C virus, or hepatitis D virus; or had another underlying condition other than CHB. We extracted aggregate data and used random-effects meta-analysis to pool incidence rates per 100 person-years. This study was registered with PROSPERO (CRD42023431652).

[FINDINGS] Of 13 231 studies screened, 71 met the inclusion criteria. A concentration-response relationship was observed between single baseline HBV DNA measurements and hepatocellular carcinoma incidence rates per 100 person-years: 0·131 (95% CI 0·097 to 0·177, I=0%) for HBV DNA concentrations <200 IU/mL, 0·176 (0·117-0·266, I=88%) for <2000 IU/mL, 0·311 (0·245-0·393, I=13%) for 2000-19 999 IU/mL, 0·862 (0·725-1·026, I=0%) for 20 000-199 999 IU/mL, and 0·941 (0·668-1·324, I=58%) for ≥200 000 IU/mL (p<0·0001 for between-group difference). Similar concentration-response patterns were observed for development of cirrhosis (0·298 [95% CI 0·214-0·415], two studies, for <200 IU/mL; 0·300 [0·146-0·616], I=88%, for <2000 IU/mL; 0·712 [0·624-0·814], I=46%, for 2000-19 999 IU/mL; 1·436 [0·991-2·082], I=76%, for 20 000-199 999 IU/mL; and 2·193 [1·690-2·846], I=82%, for ≥200 000 IU/mL) and liver-related mortality (0·086 [95% CI 0·054-0·136], one study; 0·083 [0·015-0·451], I=0%; 0·303 [0·228-0·402], I=0%; 0·766 [0·591-0·993], one study; and 1·118 [0·951-1·314], two studies), but no concentration-response relationship was observed between a single baseline HBV DNA assessment and all-cause mortality or liver decompensation. Compared with ALT below the ULN, incidence rates of hepatocellular carcinoma, cirrhosis, and liver-related mortality were higher in individuals with baseline ALT concentrations 1·0-1·9 × ULN or ≥2·0 × ULN. A similar pattern was not found for all-cause mortality, and other outcomes were not meta-analysed due to small numbers. Within the HBV DNA strata of <2000 IU/mL, 2000-19 999 IU/mL, and ≥200 000 IU/mL, hepatocellular carcinoma incidence rates were 2-3 times higher in individuals with ALT 1·0-1·9 × ULN than in those with ALT concentrations less than the ULN. Individuals with persistently low HBV DNA concentrations (<2000 IU/mL) or persistently normal ALT concentrations across multiple assessments had slightly lower hepatocellular carcinoma incidence rates compared with those assessed by a single measurement. Our risk of bias assessment found 15 (21%) of 71 studies to be rated as good quality, 40 (56%) as fair quality, and 16 (23%) as poor quality.

[INTERPRETATION] These findings, alongside the linked systematic review and meta-analysis of antiviral treatment efficacy, supported the 2024 WHO guidelines expansion of treatment criteria to include individuals with HBV DNA concentrations >2000 IU/mL and ALT concentrations above the ULN. For those with HBV DNA concentrations <2000 IU/mL and persistently normal ALT concentrations, treatment can be deferred.

[FUNDING] WHO.