RESUMO
BACKGROUND: The polymerase chain reaction (PCR) assay, introduced as a fast and sensitive diagnostic method, has been known to be useful in detecting Mycobacterium tuberculosis. Therefore the purpose of this study was to evaluate the usefulness of an in-house PCR assay in the detection of Mycobacterium tuberculosis by comparing PCR results with those of conventional diagnostic techniques. METHODS: We assessed the diagnostic yield of the in-house PCR assay retrospectively based on the patient's medical records using data from previously evaluated specimens submitted for PCR amplification IS6110 sequences by GeneAmp PCR system 9600 (Perkin Elmer, CT, USA). All samples had been examined for detection of M. tuberculosis by acid-fast stain and culture assay and the results from the 3 methods were analyzed. RESULTS: The majority of cases (1,727 cases, 96.6%) showed concordant results between in-house PCR, AFB stain, and culture methods; only 60 cases (3.4%) displayed discordant results. The sensitivities, specificities and positive and negative predictive values of each method were as follows: 81.0%, 99.6%, 95.0% and 98.4%, respectively for the in-house PCR; 63.4%, 100%, 100% and 96.9%, respectively for AFB staining method; and 83.8%, 100%, 100% and 98.6%, respectively for culture assays. CONCLUSIONS: The PCR assay shows a high sensitivity and specificity and is a reliable test for an early diagnosis of tuberculosis.