Chlamydia trachomatis screening in resource-limited countries - Comparison of diagnostic accuracy of 3 different...

Commercially available assays were evaluated in order to determine diagnostic accuracy of Chlamydia trachomatis specific tests for screening.

The study included 225 sexually active men and women, who were tested for genital chlamydial infection in Institute of Public Health Kragujevac. Three screening tests were used: direct immunofluorescence (DIF) and rapid lateral immunochromatographic test (RT) for qualitative detection of chlamydial antigens and immunoenzyme (ELISA) test for detection of serum levels of anti-chlamydial IgA and IgG antibodies. Diagnostic efficiency of these tests were determined in relation to results obtained by RT-PCR method.

Statistical significance between the results obtained by RT-PCR as a gold standard and DIF, RT and ELISA were analyzed using chi-square (χ2) test. Statistical analysis showed a significant difference between RT-PCR and analyzed screening tests: DIF (χ2 = 303; p < 0.001), RT (χ2 = 4.19; p = 0.041), serum IgA (χ2 = 4.19; p = 0.041) and serum IgG (χ2 = 67; p < 0.001) which indicates poor agreement between these tests. Large numbers of false positive (FP) and false negative (FN) results were observed for all tested assays. According to Youden's index, serum IgG and DIF testing demonstrated the most-balanced sensitivity-specificity rate. RT assay exhibits the highest expanded Youden's index, as well as the best overall diagnostic accuracy.

None of evaluated screening tests can be recommended as individual method for the diagnosis of acute infection. We suppose that RT-PCR is unlikely to be a cost-effective screening strategy within the Serbian health system.