Comparison of culture and microscopic methods by PCR for detection of Mycobacterium tuberculosis in sputum
Background: It is difficult to diagnose Mycobacterium tuberculosis infection due to a lack of rapid, sensitive, and specific tests. Newer methods, which are easy and reliable, are required to diagnose TB at an early stage. Our aim is to evaluate the polymerase chain reaction (PCR) technique, using primers directed against the IS6110 gene, for the detection of M. tuberculosis in the sputum samples, and calculate the sensitivity and specificity of PCR.
Patients and methods: A total of 248 sputum samples from patients suspected of mycobacterial diseases were studied. DNA was extracted by boiling method. IS6110 PCR method by a specific pair of primers designed to amplify 123bp and 245bp sequences of the insertion sequence, 6110, in the M. tuberculosis genome was used to analyze sputum samples.
Results: Totally, 32 (12.9%) samples had positive culture. PCR yielded a sensitivity of 93.8% and specificity of 99.1% for the diagnosis of TB, when diagnosis was confirmed by culture. There were 2 out of 32(6.3%) PCR-positive cases among the patients with non-TB disease.
Conclusion: We concluded that the performance of an IS6110 PCR assay is valuable in the rapid diagnosis of tuberculosis.