Evaluation of the Bio-Rad syphilis IgG test performed on the CODA system for serologic diagnosis of syphilis.

The performance of the Bio-Rad Syphilis IgG EIA test as a "screen for syphilis" [testing first by EIA and then by the rapid plasma reagin (RPR) assay if the EIA was positive or equivocal] and as a confirmatory test was evaluated by comparing results to those obtained by CAPTIA Syphilis-G. Discrepancies were resolved by repeating both EIAs and/or the SeroDia TP-PA (a particle agglutination assay that replaced the microhemagglutination Treponema pallidum test). Both EIAs were totally automated, the Bio-Rad test using the AutoPrep instrument for pipetting and the CODA system to perform all of the steps required to complete the EIA and interpret results, and the CAPTIA test using the LabOTech(R) to accomplish both functions. Of 449 unselected sera submitted to "screen for syphilis," both EIAs agreed for 432 (96.2%) specimens: 395 negative, 36 positive, and one equivocal. Fifty-four specimens were positive or equivocal by one or both EIAs; 41 of these were RPR reactive. Three of these 41 were incorrectly called negative by Bio-Rad (sensitivity 92.7%), and there was 1 false-negative result by CAPTIA (sensitivity, 97.6%) (P, not significant). To further evaluate the Bio-Rad assay as a confirmatory test, 144 known RPR-reactive specimens were tested by both EIAs. Results agreed for 134 (93.1%): 123 positive, 11 negative. After resolving discrepancies, there were 3 false-negative and no false-positive results by Bio-Rad (sensitivity 97.8%, specificity 100%), and with CAPTIA there were no false-negative results and 1 false-positive (sensitivity 100%, specificity 91.7%) (P, not significant). The sensitivity of the Bio-Rad assay could be improved, without altering specificity, by lowering the cut-off value for equivocal results. In summary, the Bio-Rad Syphilis IgG EIA performed using the AutoPrep instrument and CODA system is a reliable, efficient method of syphilis testing.

Evaluation of the ESP Culture System II for recovery of mycobacteria from blood specimens collected in isolator tubes.

The reliability of the ESP Culture System II (ESP II; AccuMed International, Westlake, Ohio), a continuously monitoring, nonradiometric mycobacterial culture system, for recovery of mycobacteria from sediments of blood collected in an Isolator tube was evaluated by comparing its performance to inoculation of the sediment onto Middlebrook 7H11/7H11 selective biplates. Of 1,704 blood specimens, 73 (4.3%) were positive for mycobacteria (68 Mycobacterium avium complex and 5 M. tuberculosis). Fifty-three specimens were positive by both methods; 13 were positive by ESP II only, and 7 were positive by Middlebrook agar only (chi square = 1.8; P > 0.05). The mean times to positivity were 15.6 days for ESP II and 19.0 days for Middlebrook agar (P < 0.01). The time to detection was the same for 13 specimens; ESP II was positive first for 33, and agar plates were positive first for 7. ESP II allowed recovery of more mycobacteria (90.4% of all isolates versus 82.2% for Middlebrook agar) from sediments of blood specimens collected in Isolator tubes, and it provided significantly faster detection than did Middlebrook plates.

Use of the Treponema pallidum-specific captia syphilis IgG assay in conjunction with the rapid plasma reagin to test for syphilis.

The Captia Syphilis IgG enzyme immunoassay (EIA) was evaluated for use in conjunction with the rapid plasma reagin test (RPR) as a method to test for syphilis. A total of 1,288 serum specimens were tested by the routine laboratory protocol of the RPR followed by microhemagluttination assay for Treponema pallidum (MHA-TP) testing of RPR-reactive sera as well as the EIA-RPR protocol in which the automated EIA followed by a manual RPR test for EIA-positive specimens is used. When using the routine protocol, 131 specimens were initially reactive by the RPR, and 113 of these were reactive by MHA-TP. When using the EIA-RPR protocol, 170 specimens were initially positive by EIA, and of these, 112 were RPR reactive, indicating active disease. When compared to the routine protocol, the EIA-RPR protocol had sensitivity, specificity, and positive and negative predictive values of 96.5, 99.7, 97.3, and 99.7%, respectively. After resolution of discrepancies by additional testing, the adjusted sensitivity, specificity, and positive and negative predictive values were 100, 99.8, 98.3, and 100%, respectively. This evaluation demonstrates that when used in conjunction with the RPR, the Captia Syphilis EIA is a reliable method by which to test for syphilis.