A recent study (J Pediatrics 2014; 165: 773-8) highlighted the clinical problem of discrepant hepatitis B virus (HBV) testing in pregnant women.
Design: The Centers for Disease Control and Prevention analyzed a nonrandom sample of discordant cases of HBV reported by US Perinatal Hepatitis B Prevention Program. Discordant cases indicated that there were differences between an initial HBsAg result and a subsequent test. Among 142 cases, 89 had sufficient information to determine accuracy of the initial test.
Key finding: 14 (15.7%) of these cases were true positives, the remainders were false-positives.
How did authors sort out cases?
Negative testing for “total anti-HBc or no detectable HBV DNA result indicating no HBV infection…A positive total anti-HBc indicates current or past HBV infection, is not elicited by vaccination, and usually persists for life.”
Pointers regarding serology:
- IgM anti-HBc -acute or recent infection and can persist for more than 6 months.
- HBV DNA confirms active infection and can detect infection at levels below those of HBsAg assays. This can occur either due to “occult HBV infection” or due to a mutant HBV strain that results in non-reactive test for HBsAg.
- There were at least 11 HBsAg assays that have been FDA-approved –most but not all of them will confirm results before reporting.
It is important to sort out patients with discrepant HBV serology. In infants who are not identified with HBV testing (false-negatives), this results in suboptimal post exposure prophylaxis and increased likelihood of chronic HBV. Whereas, infants with false-positive results, incur unnecessary prophylaxis and costs. The authors note that “total anti-HBc was the most useful single test to resolve HBsAg discrepancies.
Also noted: J Pediatr 2014; 165: 767-72. “Factors Affecting the Natural Decay of Hepatitis B Surface Antigen in Children with Chronic Hepatitis B Virus Infection during Long-Term Followup” This study followed 349 Taiwanese children over 20 years and noted annual HBsAg clearance of 0.58% (42 cleared HBsAg). Spontaneous clearance was more common in HBeAg-seroconverters, infants with low initial HBsAg level <1000 IU/mL, and to those born to non-HBsAg-carrier mothers.