Comparison of polymerase chain reaction for IS6110 and Amplicor in the diagnosis of tuberculosis.

BACKGROUND: Polymerase chain reaction (PCR) amplification of Mycobacterium tuberculosis DNA offers the potential of a sensitive and specific diagnostic test for tuberculosis. To evaluate this technique from the clinician's perspective, samples were collected from patients with chronic respiratory disease and the sensitivity and specificity of a newly introduced commercially available PCR kit (Amplicor) was compared with that of an established method to detect the target sequence IS6110. METHODS: Sputum or bronchial washings from patients with active tuberculosis, previously treated tuberculosis or other selected respiratory illnesses were analysed by both techniques and their sensitivity and specificity determined. RESULTS: Amplicor was more specific than IS6110 in the diagnosis of active infection (98% versus 79%). Both techniques were equally sensitive (92%). CONCLUSION: These results suggest that analysis of respiratory samples by Amplicor PCR in inner city populations of patients has greater specificity for a diagnosis of active tuberculosis than PCR for IS6110, and thus Amplicor PCR may aid the clinician in making a diagnosis of active tuberculosis.