[Efficacy of Human Immunodeficiency Virus (HIV) Antigen-Antibody Combination Assay as a Screening Test and Factors Causing False-Positivity].

Purpose: We aimed to evaluate the performance of an HIV antigen-antibody combination assay (fourth-generation) by comparing it with second generation assays that detect anti-HIV. Methods: A total of 105,439 HIV screening tests were performed from January 2004 to March 2015; the second - and fourth generation assays were used for 75,302 and 30,137 samples, respectively. Samples positive on a screening test were confirmed by anti-HIV-1 western blotting (WB) and nucleic acid amplification. By the results of confirmation tests, the efficacies of the second and fourth generation assays were estimated. The clinical backgrounds with false-positive samples were examined. Results: Of 75,302 samples, 136(0.18%) were positive by the second-generation assay; 14 were confirmed positives, and 122 were false positives. Of 30,137 samples, 18(0.06%) were positive by the fourth-generation assay; 6 were confirmed positives, and 12 were false positives. The reliability of the positives by fourth-generation assay was significantly improved (p=0.006) Samples form individuals with malignant neoplasms were frequently false positive by both the second and fourth-generation assays. Of 67 samples performed by WB, 10 samples, including 6 from patients with a malignancy, showed indeterminate results. All indeterminate samples were found to have antibodies responding to HIV core protein. Conclusion: The fourth-generation assay had satisfactory reliability of the positives for HIV screening. Antibodies responding to HIV core protein may result in false positive HIV screening tests. [Original]

[Comparative Study for Anti-Hepatitis B Surface Antigen Titers Based on Two Measurement Methods: Using Monoclonal Antibodies Isolated from Hepatitis B Vaccinated Recipients].

BACKGROUND: As anti-hepatitis B surface antigen (anti-HBs) titers vary depending on the measurement methods, we compared two different methods to measure anti-HBs titers in sera and HBs monoclonal antibodies. METHODS: The sera from 182 HB virus-resolved patients who were negative for HBsAg but positive for antiHB core protein (HBc) and/or anti-HBs were obtained. The measurement of anti-HBs was compared using either Lumipulse G1200 or Architect i2000SR. Six different monoclonal antibody (mAbs) clones isolated from healthy individuals inoculated with hepatitis B vaccine Bimmugen (genotype C) were used. RESULTS: A statistically significant correlation in anti-HBs titers was found between the two methods tested (Y = 0.951X + 100.7, R = 0.813, p < 0.001), although anti-HBs titers in 72 samples (39.6%) measured by Architect were less than 50% of that by Lumipulse and 12 (6.6%) were opposite results. Measuring 2 mAbs with HBV neutralizing activity, the titers of the 116 antibody (1.0 µg/mL) were comparable (689.3 mIU/mL by Lumipulse and 440.7 mIU/mL by Architect), whereas those of the 478 antibody (1.0 µg/mL) were much lower by Architect than by Lumipulse (42.6 vs. 818.6 mIU/mL, respectively). Of four other mAbs without HBV neutralizing activity, equal titers were observed for one; two mAbs had less anti-HB titers by Architect; and one was below the cut-off index (< 5 mIU/mL). CONCLUSIONS: Anti-HBs titers measured by Architect are likely to be lower than by Lumipulse, and the potential ability to detect the 478 antibody with neutralizing activity is low, indicating that Architect might underestimate anti-HBs titers. Future studies should standardize the anti-HBs titer measurement system.