Improved diagnostic potential of polymerase chain reaction by amplification of multiple gene targets in osteoarticular tuberculosis

Abstract

Purpose: Till date, a number of primers have been described for the diagnostic polymerase chain reaction (PCR) assays for tuberculosis (TB). However, most investigators have evaluated PCR's clinical utility using only one primer specific for Mycobacterium tuberculosis. The purpose of this study was to evaluate the efficacy of PCR tests targeting two different DNA sequences – insertion sequence 6110 (IS6110) and protein antigen b (Pab), in the same set of clinical samples from osteoarticular TB cases, and to evaluate if the sensitivity of the assay is improved. Materials and Methods: Twenty clinical samples obtained from osteoarticular TB cases were subjected to two different PCR assays - 123 base pair (bp) sequence coding for IS6110 and 419 bp sequence coding for Pab. Ten clinical samples from cases of proven septic arthritis were studied as controls. Results: The sensitivity of IS6110 PCR and Pab PCR were found to be 75% and 80%, respectively, and the specificity of both IS6110 PCR and Pab PCR was 100%. No significant difference was found between two PCR assays (P > 0.05). However, there were two cases which were negative by IS6110 PCR but were positive by Pab PCR. There was one case which was positive by IS6110 but was negative by Pab PCR. Seventeen out of 20 samples showed concordance between the results of two PCR tests, increasing the sensitivity to 85%. Conclusion: The diagnostic yield of the PCR test can be improved with the simultaneous amplification of two or more gene targets.