For a study, researchers wanted to determine chronic HBV phenotypes in a large cohort of children from the United States and Canada by comparing recently published population-based upper limit of normal alanine aminotransferase levels (ULN ALT) with local laboratory ULN; and to identify relationships with host and viral factors. Chronic hepatitis B virus (HBV) infection has been classified into stages or phenotypes, which may be related to prognosis and treatment indications. The Hepatitis B Research Network’s baseline enrollment statistics for children were analyzed. The following phenotype definitions were used: inactive carrier: Immune-tolerant: HBeAg-positive with high HBV DNA but normal ALT levels; or chronic hepatitis B: HBeAg-positive or -negative with high HBV DNA and abnormal ALT levels.

A total of 371 people were examined, 274 of them were HBeAg-positive (74%). Younger individuals were more likely to have HBeAg and higher HBV DNA levels. When local laboratory ULN ALT levels were utilized, 35% were assigned the immune tolerant phenotype; however, when updated ULN values were used, only 12% could be characterized as immune tolerant, and the remaining 82% were judged to have chronic hepatitis B. Only 21 (22%) of HBeAg-negative patients were identified as inactive carriers, and 14 (14%) as HBeAg-negative chronic hepatitis B; the majority (61%) had abnormal ALT and low levels of HBV DNA, indicating an indeterminate phenotype. Age was related to a lower frequency of HBeAg-positive infection. The immunological tolerant phenotype is unusual in children with chronic HBV infection in North America, and HBeAg positivity declines with age.