Poor efficacy of nucleic acid testing in identifying occult HBV infection and consequences for safety of blood supply in Italy.

BACKGROUND & AIMS: In Italy, DNA screening of blood donations for hepatitis B virus (HBV) was introduced to prevent the transmission of window period and occult HBV infection. Anti-HBc screening is not recommended in order to avoid shortage of the blood supply. To contain costs, donor samples are generally pooled before testing. We evaluated the safety of this national policy using a prospective repository of donors/recipient pairs. METHODS: We used highly sensitive nucleic acid testing (NAT) assays to test repository and follow-up samples from donors who were initially classified as negative by minipool NAT assays (6-MP), but were later found to carry occult HBV DNA. When available, we also analysed recipients' pre- and post-transfusion samples, collected in the context of a repository financed by the European Commission (the BOTIA project). RESULTS: Between 2008 and 2011 6-MP NAT assays identified 18 carriers of occult HBV infection among 12,695 donors; 28 samples from previous donations were available from 13 of these carriers. Highly sensitive HBV DNA detection methods showed that 6-MP HBV DNA screening failed to identify 14/28 (50%) viraemic donations, that were released for transfusion. HBV marker testing of such blood product recipients revealed two cases of transfusion transmitted HBV infection, documented by donor-recipient sequence identity. CONCLUSIONS: Viraemic blood donations from occult HBV infection carriers remain undetected by current minipool HBV DNA screening, and transfusion transmission of HBV continues to occur in susceptible patients. More effective individual HBV DNA screening and/or tests for antibodies to HBV core antigen should be considered to improve blood safety.

A cluster of human immunodeficiency virus Type 1 recombinant form escaping detection by commercial genomic amplification assays.

BACKGROUND: Nucleic acid testing (NAT)-based methods for the detection and quantification of human immunodeficiency virus Type 1 (HIV-1) RNA are used to increase transfusion safety and to diagnose and manage HIV-1-infected patients. We describe a novel HIV-1 recombinant form associated with lack of reactivity or substantial underestimation of viral load by commercial NAT assays. STUDY DESIGN AND METHODS: We observed a repeat blood donor seroconverting to anti-HIV in whom HIV RNA was initially undetectable with routine NAT was observed. During donor follow-up, HIV RNA became detectable, but the viral load was 2 to 3 log lower than measured with other NATs targeting different genome regions. Genome sequencing revealed a novel B/F recombinant with mutations affecting primers and probe annealing accounting for the poor performance of routine NAT. A total of 553 HIV-1-infected patients attending the hospital clinic were subsequently tested prospectively using the routine assay and an in-house assay specifically designed to detect the B/F strains. RESULTS: The routine assay substantially underestimated viremia (1-5 log) in 19 cases (3.5%), 11 (58%) of which were infected with the same B/F strain observed in the index donor samples. Two other non-B circulating recombinant forms of HIV-1 (A/G, B/G subtypes) were identified as poorly detected. Newly introduced NATs targeting two HIV-1 regions improved assay performance. CONCLUSION: HIV-1 increasing heterogeneity affects the efficiency of NATs and consequently the safety of the blood supply as well as diagnosis and patient management.