Screening of occult HBV infection in blood donors in Hong Kong using nucleic acid testing

Abstract

BACKGROUND AND AIMS: Post-transfusion hepatitis B infection can still occur with HBsAg-negative blood donors. This is believed to be caused by occult HBV infection, defined by detectable HBV DNA in HBsAg-negative subjects. We aimed to determine the prevalence of occult HBV infection in blood donors in Hong Kong with high endemicity for chronic hepatitis B. PATIENTS AND METHODS: From January 2006 to September 2007, we prospectively collected serum samples from 10,000 blood donors at the Hong Kong Red Cross Transfusion Service. Sera were screened by the Cobas TaqScreen MPX Test in the s201 system (Roche diagnostics). In subjects with initial positive results, occult HBV status was confirmed by the Artus HBV PCR [lower limit of detection (LLOD): 6.4 copies/mL] (Qiagen), Cobas TaqMan (LLOD: 69.8 copies/mL) (Roche diagnostics), and an in-house real-time PCR tests (LLOD: 26 copies/mL). Genuine HBV DNA positive result was defined as having 2 out of 3 positive HBV DNA signals by the Artus test. RESULTS: We identified 61 HBsAg-negative, s201-positive cases. Artus HBV test revealed that 43 cases had 2 consecutive negative PCR signal, while 7 cases had only 1 positive PCR result out of 3 tests. Eleven cases had 2 positive HBV DNA results out of 3 tests (range: 0.7−53.9 copies/mL). Thus 11 out of 10,000 donors (0.11%) had confirmed occult HBV infection. Six samples were tested with Cobas TaqMan test and in-house real-time PCR. HBV DNA was undetectable in all 6 samples by the Cobas TaqMan test and detectable in 1 sample by the in-house real-time PCR test. At the time of writing, 5 subjects (3 male, 2 female) underwent liver biopsies. One female subject had normal histology and the other female had mild necroinflammation. Two male subjects had mild to moderate fibrosis, and one male subject had moderate steatosis. CONCLUSIONS: The prevalence of occult HBV infection was 0.11% among blood donors in Hong Kong. Due to the extremely low HBV DNA levels in these subjects, it is difficult to accurately diagnose occult HBV infection. Liver histology however showed that some subjects had developed fibrosis and other mild hepatic changes.