Comparative study of diagnostic accuracy of established PCR assays and in-house developed sdaA PCR method for detection of Mycobacterium tuberculosis in symptomatic patients with pulmonary tuberculosis.

OBJECTIVES: Indian contribution to global burden of tuberculosis is about 26%. In the present study we have developed an in-house PCR assay using primers for sdaA gene of Mycobacterium tuberculosis and evaluated against already established primers devR, IS6110, MPB64, rpoB primers for diagnosis of pulmonary tuberculosis.
METHODS: Using universal sample preparation (USP) method, DNA was extracted from sputum specimens of 412 symptomatic patients from Delhi, India. The DNA so extracted was used as template for PCR amplification using primers targeting sdaA, devR, IS6110, MPB64 and rpoB genes.
RESULTS: Out of 412, 149 specimens were considered positive based on composite reference standard (CRS) criteria. The in-house designed sdaA PCR showed high specificity (96.5%), the high positive likelihood ratio (28), the high sensitivity (95.9%), and the very low negative likelihood ratio (0.04) in comparison to CRS.
CONCLUSION: Based on our results, the sdaA PCR assay can be considered as one of the most reliable diagnostic tests in comparison to other PCR based detection methods.