Use of Polymerase Chain Reaction for Primary Diagnosis of Pulmonary Tuberculosis in the Clinical Laboratory

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Abstract
A nested polymerase chain reaction (PCR) has been used for the rapid detection of tubercule bacilli in respiratory specimens from 287 patients suspected of tuberculosis. The results of PCR testing were compared with isolation methods (conventional culture and Bactec system) in 110 smear-positive and 177 smear-negative patients. There were only 4 false negative results by PCR in the 171 specimens that were M. tuberculosis complex culture-positive. Of 92 PCR-positive samples prepared from the smear-positive specimens 90 (97.8%) were confirmed by culture. However, a poor correlation was obtained between initial 122 PCR-positive results and combined 81 culture recovered organisms in smear-negative patients. After verification of the efficacy of isolation method, retesting PCR-positive culture-negative samples, and studies of patients' clinical histories, only 18 of the cases were found to be associated with the disease. The other 29 results out of the original 47 discrepants were considered PCR false positives, possibly due to contamination. In conclusion, the PCR assay described is suitable for implementation in daily routine work with respiratory specimens, however it should be validated with culture, especially for the smear-negative patients.