Hepatitis B Core Related Antigen - Does it meet our expectations? Evidence from Cohorts in the United Kingdom and South Africa

IntroductionBetter understanding of hepatitis B virus (HBV) biomarkers is needed. We evaluated Hepatitis B core related antigen (HBcrAg), in the United Kingdom (UK) and South Africa (SA). MethodsWe undertook a cross-sectional retrospective observational study of adults with chronic HBV infection from the UK (n=142) and SA (n=211). We recorded clinical and laboratory parameters and quantified HBcrAg. We report HBcrAg distribution, relationship with other biomarkers, and performance in risk stratification based on point of care test (POCT) thresholds. ResultsSA and UK cohorts were similar in sex and age (p>0.05), but significantly different in ethnicity, HIV coinfection, HBeAg-positivity and proportion with HBV viral load (VL) >200,000 IU/ml (all p<0.001). More of the untreated SA population had HBcrAg >5.3 log10U/ml compared to the UK (33% vs 9% respectively, p<0.0001). HBcrAg [&ge;]4.3 log10U/ml (corresponding to a positive POCT) was 100% sensitive and 92% specific for predicting VL >200,000 IU/ml in the UK, but not SA. HBcrAg positively correlated with alanine transferase (ALT) (p<0.001 in UK, p<0.01 in SA), and fibrosis/cirrhosis by APRI score (p = 0.03 in UK and p=0.008 in SA), but not by elastography or FIB-4 scores. DiscussionHBcrAg distribution and relationship with other biomarkers differs between settings. HBcrAg (including POCT) may be a useful proxy for VL, but less so as a marker of disease progression, Its use needs tailoring to represent diverse populations.