ROUTINE APPLICATION OF THE POLYMERASE CHAIN-REACTION FOR DETECTION OFMYCOBACTERIUM-TUBERCULOSIS IN CLINICAL-SAMPLES

Aim-To investigate the use of the polymerase chain reaction (PCR) in t he routine laboratory for the detection of Mycobacterium tuberculosis in clinical samples. Methods-Samples were divided and processed separa tely for the detection of M tuberculosis by microscopy, culture and PC R. After DNA extraction, PCR was performed with primers specific for t he insertion element IS6110 and the product was analysed by agarose ge l electrophoresis, Southern blotting or dot blotting and hybridisation with a digoxigenin labelled internal probe. Each sample was tested fo r inhibitors of Tag polymerase with the aid of an internal control. Mu ltiple negative and positive controls were used to monitor each step o f the procedure. Results-The data from two laboratories, using the sam e operating procedures, were combined. Of 1957 specimens, 79 (4%) were culture and PCR positive, while 1839 (93.9%) were negative in both te sts. Thirty specimens (1.5%) were PCR positive only and nine (0.5%) we re culture positive but PCR negative. Conclusion-Using culture and cli nical history as the gold standard, sensitivity and specificity for PC R were 92.1% and 99.8%, respectively. With elaborate precautions, PCR is a suitable and reliable method for the detection of M tuberculosis in clinical samples in a routine microbiology laboratory.