[Routine direct detection of Mycobacterium tuberculosis with a rapid test of polymerase chain reaction applied to a...

The results of the present study, based on 1869 examined clinical specimens of 543 patients, represent the Hungarian parameters of a PCR test. By using the final and resolved results, the clinical sensitivity, specificity, positive and negative predictive values were 83.8%, 99.2%, 95.4% and 97%, respectively for PCR, 63.5%, 100%, 100% and 93.5%, respectively for culture, and 16.2%, 100%, 100% and 86.3%, respectively for Ziehl-Neelsen (ZN) staining. These results are essential to allow Hungarian clinicians to interpret PCR results in accordance with local conditions. The present study has demonstrated a high sensitivity (PCR vs. culture and smear, p < 0.01) and an excellent specificity of PCR. Our results indicate that the majority of M. tuberculosis-positive specimens can be identified rapidly with the test and, because of the high negative predictive value, the PCR test can help to exclude tuberculosis from the differential diagnosis in 24 hours. Moreover, the PCR can detect the presence of M. tuberculosis in 66.6% of ZN-negative and subsequently culture-positive specimens at the time of admission. The results of PCR must be interpreted with extreme caution, and the procedure is recommended only for laboratories, which simultaneously perform culture and microscopy for control of the performance of PCR tests.