The importance of polymerase chain reaction amplification for the diagnosis of Mycobacterium tuberculosis

Abstract

Polymerase chain reaction (PCR) technique, has recently been applied in the rapid amplification and identification of Mycobacterium tuberculosis. In the present study PCR method was used to test 106 clinical specimens from 36 patients in whom tuberculosis was suspected. The results were correlated with the results of clinical examination, radiological findings, skin test results, biochemical, pathologic and bactériologie findings (Ziehl-Neelson acid fast stain method and culture method). The sensibility, specificity, positive predictive value and negative predictive value of PCR results were 85.0 %, 89.5 %, 65.3 %, and 96.2 % respectively in our series if we accept culture results as the 'Gold Standart'. The sensibility and specificity were similar as reported in previous reports. Of 36 cases, 5 were found to be positive for Mycobacterium tuberculosis by both bactériologie and PCR techniques. Additional 5 cases were positive in either bactériologie or PCR techniques. In 4 out of 5 patients, only DNA amplification method was positive. Further clinical examination, laboratory findings and clinical follow up of the cases with PCR positive results supported tuberculosis in 3 out of 4 cases. In 1 out of 4 cases, further clinical examination and laboratory findings revealed mycoplasma infection and treated with nontuberculosis drugs. The PCR positive results in this case may be explained by bacilli contamination in laboratory condition. The only case who had negative PCRfindings with positive culture results treated as tuberculosis successfully. In this case negative PCR results with positive culture results may be the result of the existence of no or fewer bacilli in reaction mixture. The application of PCR in the diagnosis of tuberculosis in clinical specimens with high sensibility and specificity represent us the usefulness of PCR in clinical diagnosis of tuberculosis.