[Detection of Mycobacterium tuberculosis in sputum by polymerase chain reaction]

A method based on DNA amplification (PCR) and hybridization for the detection of M. tuberculosis was used to test 86 sputum specimens from 52 patients in whom tuberculosis was suspected. M. tuberculosis was detected in 35 specimens, with 1 false positive. The finding was negative in 51 specimens, of which 4 were false negative. Thirty-two specimens were positive by standard microbiological criteria (acid-fast stain and culture), and 54 specimens were negative (including 6 false negative). Of 38 specimens with definite diagnosis of tuberculosis, 89.5% (34/38) were positive by DNA amplification and 84.2% (32/38) by acid-fast stain and/or culture. The difference is not statistically significant (P > 0.05). The specificity was 97.9% (47/48) and 100% (48/48) by DNA amplification and acid-fast stain and/or culture, specificity was 97.9% (47/48) and 100% (48/48) by DNA amplification and acid-fast stain and/or culture, individually, and difference is also not statistically significant (P > 0.05). However, PCR combined with specific DNA probe is more sensitive than the acid-fast stain method and faster than the culture method. Therefore it is useful for early detection of pulmonary mycobacterial infection.