Diagnostic efficacy of a real time-PCR assay for Chlamydia trachomatis infection in infertile women in north India

BACKGROUND & OBJECTIVES Little is known about the prevalence of Chlamydia trachomatis infection in Indian women with infertility. To improve the diagnosis of C. trachomatis infection in developing countries, there is an urgent need to establish cost-effective molecular test with high sensitivity and specificity. This study was conducted to determine the diagnostic utility of a real time-PCR assay for detention of C. trachomatis infection in infertile women attending an infertility clinic in north India. The in house real time-PCR assay was also compared with a commercial real-time PCR based detection system. METHOD Endocervical swabs, collected from 200 infertile women were tested for C. trachomatis by three different PCR assays viz. in-house real time-PCR targeting the cryptic plasmid using published primers, along with omp1 gene and cryptic plasmid based conventional PCR assays. Specimens were also subjected to direct fluorescence assay (DFA) and enzyme immunoassay (EIA) Performance of in-house real time-PCR was compared with that of COBAS Taqman C. trachomatis Test, version 2.0 on all in-house real time-PCR positive sample and 30 consecutive negative samples. RESULTS C. trachomatis infection was found in 13.5 per cent (27/200) infertile women by in-house real time-PCR, 11.5 per cent (23/200) by cryptic plasmid and/or omp1 gene based conventional PCR, 9 per cent (18/200) by DFA and 6.5 per cent (7/200) by EIA. The in-house real time-PCR exhibited a sensitivity and specificity of 100 per cent, considering COBAS Taqman CT Test as the gold standard. The negative and positive predictive values of the in-house real time-PCR were 100 per cent. The in-house real time-PCR could detect as low as 10 copies of C. trachomatis DNA per reaction. INTERPRETATION & CONCLUSIONS In-house real time-PCR targeting the cryptic plasmid of C. trachomatis exhibited an excellent sensitivity and specificity similar to that of COBAS Taqman CT Test, v2.0 for detection of C. trachomatis infection in women attending an infertility clinic. In an effort to prevent Chlamydia infection associated infertility, we recommend screening of women with infertility due to C. trachomatis infection by in-house molecular method as a cost-effective solution in resource limited settings.