Evaluation of polymerase chain reaction, tuberculostearic acid analysis, and direct microscopy for the detection of Mycobacterium tuberculosis in sputum

Tuberculosis remains a major global cause of morbidity and mortality. There is an urgent need for improved bacteriologic diagnosis of Mycobacterium tuberculosis infection. Three methods for rapid identification of M. tuberculosis in sputum samples (direct microscopy, gas chromatography-mass spectrometry [GC-MS], and polymerase chain reaction [PCR]), were compared with culture on Lowenstein-Jensen medium. Growth of M. tuberculosis was observed in 38 of 145 sputum samples. Detection of acid-fast bacilli by direct microscopy gave a sensitivity of 66% and a specificity of 100%. Detection of tuberculostearic acid by GC-MS gave a sensitivity of 55% and a specificity of 87%. Amplification by PCR of a fragment of the insertion sequence IS6110 gave a sensitivity of 95% and a specificity of 93% compared with culture and a corrected specificity of 99% compared with both culture and clinical data. This study indicates that PCR can be adapted for clinical use and is the method of choice for rapid diagnosis of pulmonary tuberculosis.