Efficacy of individual nucleic acid amplification testing in reducing the risk of transfusion-transmitted hepatitis B virus infection in Switzerland, a low-endemic region.

BACKGROUND: The risk of transfusion-transmitted hepatitis B virus (HBV) in Switzerland by testing blood donors for hepatitis B surface antigen (HBsAg) alone has been historically estimated at 1:160,000 transfusions. The Swiss health authorities decided not to introduce mandatory antibody to hepatitis B core antigen (anti-HBc) testing but to evaluate the investigation of HBV nucleic acid testing (NAT). STUDY DESIGN AND METHODS: Between June 2007 and February 2009, a total of 306,000 donations were screened routinely for HBsAg and HBV DNA by triplex individual-donation (ID)-NAT (Ultrio assay on Tigris system, Gen-Probe/Novartis Diagnostics). ID-NAT repeatedly reactive donors were further characterized for HBV serologic markers and viral load by quantitative polymerase chain reaction. The relative sensitivity of screening for HBsAg, anti-HBc, and HBV DNA was assessed. The residual HBV transmission risk of NAT with or without anti-HBc and HBsAg was retrospectively estimated in a mathematical model. RESULTS: From the 306,000 blood donations, 31 were repeatedly Ultrio test reactive and confirmed HBV infected, of which 24 (77%) and 27 (87%) were HBsAg and anti-HBc positive, respectively. Seven HBV-NAT yields were identified (1:44,000), two pre-HBsAg window period (WP) donations (1:153,000) and five occult HBV infections (1:61,000). Introduction of ID-NAT reduced the risk of HBV WP transmission in repeat donors from 1:95,000 to 1:296,000. CONCLUSIONS: Triplex NAT screening reduced the HBV WP transmission risk approximately threefold. NAT alone was more efficacious than the combined use of HBsAg and anti-HBc. The data from this study led to the decision to introduce sensitive HBV-NAT screening in Switzerland. Our findings may be useful in designing more efficient and cost-effective HBV screening strategies in low-prevalence countries.

Assessment of recent HIV-1 infection by a line immunoassay for HIV-1/2 confirmation.

BACKGROUND: Knowledge of the number of recent HIV infections is important for epidemiologic surveillance. Over the past decade approaches have been developed to estimate this number by testing HIV-seropositive specimens with assays that discriminate the lower concentration and avidity of HIV antibodies in early infection. We have investigated whether this "recency" information can also be gained from an HIV confirmatory assay. METHODS AND FINDINGS: The ability of a line immunoassay (INNO-LIA HIV I/II Score, Innogenetics) to distinguish recent from older HIV-1 infection was evaluated in comparison with the Calypte HIV-1 BED Incidence enzyme immunoassay (BED-EIA). Both tests were conducted prospectively in all HIV infections newly diagnosed in Switzerland from July 2005 to June 2006. Clinical and laboratory information indicative of recent or older infection was obtained from physicians at the time of HIV diagnosis and used as the reference standard. BED-EIA and various recency algorithms utilizing the antibody reaction to INNO-LIA's five HIV-1 antigen bands were evaluated by logistic regression analysis. A total of 765 HIV-1 infections, 748 (97.8%) with complete test results, were newly diagnosed during the study. A negative or indeterminate HIV antibody assay at diagnosis, symptoms of primary HIV infection, or a negative HIV test during the past 12 mo classified 195 infections (26.1%) as recent (< or = 12 mo). Symptoms of CDC stages B or C classified 161 infections as older (21.5%), and 392 patients with no symptoms remained unclassified. BED-EIA ruled 65% of the 195 recent infections as recent and 80% of the 161 older infections as older. Two INNO-LIA algorithms showed 50% and 40% sensitivity combined with 95% and 99% specificity, respectively. Estimation of recent infection in the entire study population, based on actual results of the three tests and adjusted for a test's sensitivity and specificity, yielded 37% for BED-EIA compared to 35% and 33% for the two INNO-LIA algorithms. Window-based estimation with BED-EIA yielded 41% (95% confidence interval 36%-46%). CONCLUSIONS: Recency information can be extracted from INNO-LIA-based confirmatory testing at no additional costs. This method should improve epidemiologic surveillance in countries that routinely use INNO-LIA for HIV confirmation.