Verification of specimens positive for Chlamydia trachomatis by enzyme immunoassay (EIA) has been recommended when testing low prevalence populations. This study compared direct fluorescent antibody (DFA) and blocking antibody (BLA) verification assays in specimens presumptively positive for C. trachomatis by the Syva Microtrak II EIA. Of 1785 specimens originally tested by EIA, 96 were presumptively positive for C. trachomatis. Verification assays were concordant in 86 specimens (69 positive, 17 negative); nine of the remaining samples gave positive results in a second EIA and one was unresolved. Both verification assays gave some false-negative results. When initial EIA absorbance values were correlated with verified results, all EIA false positive results had absorbances in the low range (less than a three-fold increase over assay cutoff values). Verification of EIA results by both DFA and BLA was effective in detecting false positive results, but confining verification to low-value positive specimens could be considered for cost-effective C. trachomatis testing.
Centers for Disease Control and Prevention Recommendations for the prevention and management of Chlamydia trachomatis infections, 1993. MMWR1993; 42: (No. RR-12)
MoncadaJ.,
SchachterJ.,
BolanG. Confirmatory assay increases specificity of the Chlamydiazyme test for Chlamydia trachomatis infection of the cervix. J Clin Microbiol1990; 28:1770–1773
KelloggJ. A.,
SeipleJ. W.,
MurrayC. L.,
LeviskyJ. S. Effect of endocervical specimen quality on detection of Chlamydia trachomatis and on the incidence of false-positive results with the Chlamydiazyme method. J Clin Microbiol1990; 28:1105–1113
SchwebkeJ. R.,
StammW. E.,
HandsfieldH. Use of sequential enzyme immunoassay and direct fluorescent antibody tests for detection of Chlamydia trachomatis infections in women. J Clin Microbiol1990; 28:2473–2476
LeonardiG. P.,
SeitzM.,
EdstromR.,
CruzJ.,
CostelloP.,
SzaboK. Evaluation of three immunoassays for detection of Chlamydia trachomatis in urine specimens from asymptomatic males. J Clin Microbiol1992; 30:2793–2796
ChanE. L.,
BrandtK.,
HorsmanG. B. A. 1-year evaluation of Syva MicroTrak chlamydia enzyme immunoassay with selective confirmation by direct fluorescent antibody assay in a high-volume laboratory. J Clin Microbiol1994; 32:2208–2211