Value of direct antigen detection methods in diagnosing women with suspected genital Chlamydia trachomatis infection

Establishing a method that would allow the quick and cost- effective diagnosis ofChlamydia trachomatis (C. trachomatis) is of highest interest. We aimed to evaluate the diagnostic efficacy of direct antigen detection methods [direct fluorescent antigen detection (DFA), Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR)] in comparison to culture method, to establish the most reliable and easy technique for diagnosing of C. trachomatis in females with suspected infection. Seventy patients were selected from females attending Outpatient Gynecology Clinic, Mansoura University Hospital, who were consulting for symptoms suggestive of genital infection. Two cervical swabs were taken from each patient and examined for C. trachomatis by direct detection methods. McCoy cell culture detected by immunofluorescence was positive in 16 cases (gold standard). Direct fluorescent antigen detection (DFA), ELISA and PCR were compared to McCoy cell culture in terms of sensitivity, specificity, accuracy, positive and negative predictive values. Sensitivity of DFA was lower than its specificity. Antigen detection by ELISA was positive in 28 (40%) cases. NPV (83.33%) and PPV (32.14%). Sensitivity of PCR compared to culture was 81.25% and specificity was 90.74%. In conclusion, McCoy cell culture assay is the most reliable test but tedious. Combination of PCR and DFA tests could optimize diagnosis of female genital C. trachomatis infection. Reevaluation of ELISA depending upon multiple tests as gold standard may increase its sensitivity and specificity. Key words: Chalmydia trachomatis, direct antigen detection, polymerase chain reaction(PCR), enzyme-linked immunosorbent assay (ELISA).