Cross-reaction of clinical isolates of bacteria and yeasts with the chlamydiazyme test for chlamydial antigen, before and after use of a blocking reagent.

More than 1,000 clinical isolates of bacteria and yeasts were identified, subcultured, and tested at 10(8) colony-forming units per milliliter with the Chlamydiazyme assay to determine the variety of microorganisms which could cause false-positive results for Chlamydial antigen. False-positive Chlamydiazyme results were obtained from 27 of 465 (5.8%) gram-negative, aerobic, or facultatively anaerobic bacterial isolates (including 8 of 39 [20.5%] Neisseria gonorrhoeae and 8 of 149 [5.4%] Escherichia coli isolates) and also from 2 of 46 (4.3%) Bacteroides species isolates. No false-positive results were obtained either from 373 gram-positive bacterial isolates or from 153 yeasts. Results from 21 of 29 (72.4%) isolates that cross-reacted with Chlamydiazyme antibodies were repeatedly positive, but all 21 were confirmed as false-positive results using a blocking antibody. When an initial Chlamydiazyme result is positive, repeating the test, with and without use of the blocking antibody, appears to be effective in identifying those results (more likely from poorly collected endocervical specimens) that are falsely positive, even in the presence of high concentrations of cross-reacting bacteria. Microscopic determination of endocervical specimen adequacy also may help to minimize false-positive (and false-negative) Chlamydiazyme results.

Comparison of first-voided urine specimens with endocervical swab specimens for enzyme-linked immunosorbent assay detection of Chlamydia trachomatis in women.

OBJECTIVE: To compare first-voided urine specimens with paired endocervical swab specimens from women to determine the role of urine in complementing or replacing swab specimens for the detection of the chlamydial antigen. DESIGN: For 18 months, both endocervical swab specimens (the criterion standard) and urine specimens were tested for the chlamydial antigen, using an enzyme-linked immunosorbent assay (Chlamydiazyme, Abbott Laboratories, North Chicago, Ill). Positive results were confirmed using a blocking reagent (Abbott Laboratories) and/or a direct fluorescent antibody test (Micro-Trak, Syva, Palo Alto, Calif). A low level of chlamydial antigen (below the enzyme-linked immunosorbent assay threshold recommended by the manufacturer) was also looked for and, when found, was confirmed by the direct fluorescent antibody test. SETTING: Prenatal and family practice clinics in a 500-bed community hospital. PATIENTS: Specimens were collected from 489 random asymptomatic or symptomatic women. MAIN OUTCOME MEASURE: The detection of the chlamydial antigen from endocervical swab specimens was compared with the detection from first-voided urine specimens. RESULTS: Acceptable swab and urine specimens were obtained from 300 (61.3%) of the patients. The antigen of Chlamydia trachomatis was confirmed in 20 (6.7%) of the 300 women. Of the infected patients, the antigen was detected in both swab and urine specimens for nine patients (45%), only in the swab specimens for eight (40%), and only in the urine specimens for three (15%). Testing urine in addition to endocervical swab specimens allowed for the detection of 18% more chlamydial infections, whereas confirming the presence of the antigen below the enzyme-linked immunosorbent assay cutoff resulted in the detection of 54% more infections. CONCLUSIONS: Collecting multiple specimens and testing for low levels of chlamydial antigen may significantly improve the detection of chlamydial infections in women. First-voided urine may be an appropriate complementary specimen to endocervical swab specimens, but urine by itself does not allow for the adequate detection of the chlamydial antigen in women.