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Background: In Japan, an immunochromatographic HIV-1/2 assay has been used for local Health Care Centers to prevent HIV spread in early stages and for hospitals at night or on holidays, where automated instruments are not available. In 2009, a new immunochromatographic HIV-1/2 assay became available which detects both antigen (Ag) and antibody (Ab) simultaneously and on separate bars. This study was conducted to evaluate the clinical performance of this new assay against three HIV-1/2 assays., Methods: One immunochromatographic assay (ICA) for HIV Ab detection, one chemiluminescent enzyme immunoassay (CLEIA) for Ab detection and one ELISA for Ag/Ab combination assay were evaluated with the ICA for Ag/Ab detection. Serum samples from 955 patients were used at Osaka University Hospital, who had been tested initially for HIV infection status. The 900 were negative and 55 were positive. In addition, the samples in 10 commercially available panels [2 containing relatively rare HIV subtypes/genotypes and 8 containing seroconversion samples] were tested using all HIV assays., Results: The HIV Ag/Ab ICA showed 100% (900/900, 95% confidence interval (95 CI) 99.59 - 100%) clinical specificity and was better than 99.8% (898/900, 95 CI 99.20 - 99.97%) of the existing ICA. The CLEIA and ELISA showed 100% (600/600, 95 CI 99.39 - 100%) and 99.8% (598/600, 95 CI 98.80 - 99.96%) specificity, respectively. The HIV Ag/Ab ICA showed 100% (55/55, 95 CI 93.51 - 100%) clinical sensitivity and detected all the relatively rare HIV subtypes/genotype panels; these results were the same as the other three assays. The HIV Ag/Ab ICA detected 5 seroconversion panels earlier than antibody-only-detection assays but detected later with 2 panels than ELISA for Ag/Ab combination assay., Conclusions: The HIV Ag/Ab ICA demonstrated good performances in clinical specificity and sensitivity as a rapid assay and is a suitable assay for qualitative judgement of HIV Ag and Ab simultaneously in human serum and plasma.

Nine anti-HCV antibody screening reagents currently used in Japan were investigated for diagnostic utility. The results using sera from 500 subjects and two series of anti-HCV seroconversion panels were compared. The positive detection rates of the 9 screening tests in 500 specimens ranged from 9.6% to 12.2% and the agreements between combinations ranged from 97.0-99.4%. In the 7 two-step assays, which employ recombinant antigen solid phase and anti-human antibody detection, i.e. excluding Quick Chaser and PA, agreement ranged from 97.6-99.4%. No relationship was seen between similarities of the antigen used and agreements between the 7 reagents. For the 72 specimens that showed positive with at least one screening reagent, agreements between the 9 reagents and the confirmatory tests (RIBA III) were compared. In specimens that showed positive with multiple reagents, the positive rate of RIBA III was high, thus the possibility of the existence of the anti-HCV antibody was high. In specimens that showed positive in only a single screening reagent, the RIBA III did not test positive, suggesting that the incidence of false positives may be high. The accuracy of each screening reagent was compared to RIBA III as an accuracy standard. It was found that ARCHITECT was the best in accuracy. The distance from mean to cut-off in the anti-HCV antibody negative specimens reflected the incidence of false positives in each reagent. The anti-HCV antibody seroconversion sensitivities in the initial stage of HCV infection were also compared. The earlier detection was seen with Centaur, ELISA and ARCHITECT. Each anti-HCV antibody screening reagent in use has unique features, and it is suggested that caution be used when diagnosing HCV infection on the basis of the results of a single antibody test.

Evaluation of a Chemiluminescent Microparticle Immunoassay (CMIA) for determination of anti-Treponema pallidum (TP) antibodies, "ARCHITECT TPAb", was performed. This assay was confirmed to be a reliable anti-TP assay as it showed very good fundamental performance on reproducibility (intra-assay CV: less than 4%), assay specificity (100%, 500/500) and assay sensitivity (100%, 121/121). Since this assay showed very good dilution linearity for samples within the range of 0.59-8.38 S/CO, quantification of the immunoreactivity of anti-TP was attempted. The correction formula for quantification was successfully validated with 8 specimens. The quantified anti-TP, CMIA-QT, calculated by multiplying together the assay's corrected S/CO within the range of 0.59 - 8.38 and the sample dilution factors, showed a strong correlation with the titer of TP particle agglutination (TPPA). The clinical utility of CMIA-QT was evaluated with stored specimens from 5 primary, 5 secondary, and 5 neural syphilis patients. The clinical utility of CMIA-QT was confirmed in the same manner as that of TPPA.