title: Fine-tuning the fluorescent antibody test for chlamydial infections in pregnancy.
abstract: Endocervical specimens from 168 asymptomatic women in the second trimester of pregnancy were screened for Chlamydia trachomatis infection with both standard tissue culture methods and a direct fluorescein-conjugated monoclonal antibody assay (MicroTrak). Based on tissue culture results, the prevalence of Chlamydia trachomatis was 26.2% in this population. Compared with tissue culture, the monoclonal antibody assay's sensitivity, specificity, and positive predictive value varied depending upon how many elementary bodies were used to define a positive test. Specifically, if a cutoff of ten elementary bodies was used (as per the manufacturer's instructions), the sensitivity, specificity, and positive predictive value of this test were 86.3, 98.4, and 95.0%, respectively. At the other extreme, a cutoff of one elementary body produced a more sensitive but less specific test, with parameters of 93.2, 89.5, and 75.9%, respectively. Based on these data and operating characteristic analysis, the cutoff value defining a positive test was appropriately set at two or more elementary bodies, at least for this study population. This resulted in a sensitivity, specificity, and positive predictive value of 93.2, 95.2, and 87.2%, respectively. This monoclonal antibody assay appears to be a reasonable substitute for cell culture for Chlamydia trachomatis. However, because of varying magnitudes and implications of false-positive and false-negative tests, clinicians are urged to determine the appropriate breakpoint for their individual laboratories and patient populations before substituting the direct fluorescent antibody test for tissue culture.
authors.affiliation: Department of Obstetrics and Gynecology, Louisiana State University Medical Center, New Orleans.
authors.forename: J G
authors.initials: JG
authors.lastname: Pastorek
authors.forename: T F
authors.initials: TF
authors.lastname: Mroczkowski
authors.forename: D H
authors.initials: DH
authors.lastname: Martin
mesh_terms: D000911:Antibodies, Monoclonal; D002584:Cervix Uteri / Q000382:microbiology; D002690:Chlamydia Infections / Q000175:diagnosis* / Q000382:microbiology; D002692:Chlamydia trachomatis / Q000302:isolation & purification; D005260:Female; D005455:Fluorescent Antibody Technique; D005831:Genital Diseases, Female / Q000175:diagnosis*; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis* / Q000382:microbiology; D012680:Sensitivity and Specificity
chemical_list: D000911:Antibodies, Monoclonal