M .TUBERCULOSIS در مقايسه با نتايج كشت در تشخيص عفونت با PCR تعيين ميزان حساسيت و ويژگي تست

Determination of Sensitivity and Specificity of PCR in Comparison with Culture in Diagnosis of Infection with M. Tuberculosis

Introduction: Tuberculosis is one of the oldest diseases of human. Before application of the molecular methods, because of the long duration of diagnostic- microbiologic procedures (culture and biochemical tests), the diagnosis and beginning of the therapy required experience and clinical intelligence. The diagnostic microscopic assessment methods of the smear and culture of the specimens have their own limitations, one of which is the slow growth of mycobacteria (4-8 weeks) in the culture media. Nevertheless, achievement to the more rapid diagnostic procedures is the main aim in this regard. From the beginning of the last decade, PCR and other more rapid diagnostic assays for the diagnosis of the infections due to Mycobacterium tuberculosis have been used. Objective: Since no laboratory diagnostic procedure has been known as the alternative to the culture, this study has been done for determination of sensitivity, specificity, positive and negative predictive values of the PCR test in comparison to the culture in this center. Materials and Methods: In this study, 169 specimens from the patients with positive smears were cultured on the Lowenstein- Jensen media and after subculturing and related biochemical tests, the results obtained were compared with PCR test results (with IS 6110 target and Dra, Drb primers). Results: Obtained data showed that from 169 smear positive cases, there were 150 positive cultures and after doing biochemical tests, 86 cases were detected as Mycobacterium tuberculosis. According to these results, sensitivity, specificity, positive and negative predictive values of the PCR test in this center were 91.86%, 96.87%, 97.53% and 89.85% respectively. Conclusion: Concomitant use of PCR with culture and biochemical tests is recommended.