Identification of low HBV-DNA levels by nucleic acid amplification test (NAT) in blood donors.

Objective: To evaluate the presence of HBV-DNA in 22,765 consecutive blood donors, who donated blood in the period from January 2006 to August 2007 at a transfusion centre in Lazio, a region in central Italy with low HBV endemicity.

Methods: Each donation was individually tested using immunoenzymatic assays and nucleic acid amplification technologies (NAT). Samples that were reactive to generic NAT, Procleix Ultrio Assay were tested for HBV-DNA, HCV-RNA and HIV1-RNA by Discriminatory Procleix Ultrio NAT Assay. In samples that were reactive to generic NAT and negative for HBsAg, HCV-RNA and HIV1-RNA, HBV-DNA was further tested using Cobas TaqMan and an in-house nested PCR following an ultracentrifugation step. Sequence analysis confirmed HBV-DNA positivity.

Results: Generic NAT identified 31 (0.13%) reactive sera. HBV-DNA discriminatory NAT identified 15 positive sera; HBsAg was positive in 12 sera. Of the 5 generic NAT-reactive/discriminatory NAT-negative/HBsAg-negative sera and of the 3 HBsAg-negative/HBV-DNA discriminatory NAT-positive sera, 7 were positive to Cobas TaqMan or the in-house PCR after ultracentrifugation. The overall HBV-DNA positivity was 0.083% [19 of 22,765 donors: 12 HBsAg-positive (HBV-DNA range 10(2)-10(4) IU/mL), 7 HBsAg-negative/anti-HBc positive (HBV-DNA< 6 IU/mL)].

Conclusions: For blood transfusion safety, the significance of the finding of very low HBV-DNA levels should be further investigated. Our data indicate that in areas with a low HBV endemicity, single NAT assays may not always identify blood donations with very low HBV-DNA levels.