CLINICAL UTILITY OF THE POLYMERASE-CHAIN-REACTION IN THE DIAGNOSIS OFEXTRAPULMONARY TUBERCULOSIS

This study examines the diagnostic utility of the polymerase chain rea ction (PCR) in 156 patients (five human immunodeficiency virus (HIV) s eropositive) suspected of extrapulmonary tuberculosis. The results of PCR in 226 samples from II different sites were compared with the resu lts of microscopy and culture. Positive culture results were predicted in 86% of samples by PCR but in only 31% by miaoscopy. Specificity of PCR was 92%. In cases with culture-proven tuberculosis, PCR identifie d all 11 microscopy positive cases and 19 of 24 (79%) of the microscop y-negative cases. In four patients, PCR excluded the diagnosis of tube rculosis in microscopy-positive samples, which mere later shown to con tain mycobacteria other than Mycobacterium tuberculosis or laboratory contaminants, In 20 patients (microscopy, PCR and culture negative) a trial of antituberculous drugs was given, hut patients showed no impro vement and treatment was stopped. In 17 patients, all culture negative (in nine PCR was positive, three of whom also had positive microscopy ) the diagnosis was probable tuberculosis based on clinical findings a nd response to treatment, This polymerase chain reaction has a much hi gher sensitivity than microscopy and can facilitate therapeutic decisi ons for those with suspected extrapulmonary tuberculosis.