Diagnosis of extrapulmonary tuberculosis by a commercial polymerase chain reaction kit

The Roche Amplicor Mycobacterium tuberculosis PCR test was compared with mycobacterial culture for direct detection of M. tuberculosis in extrapulmonary specimens. From January 1995 to October 1996, 124 clinical specimens from 112 patients were assessed, including 47 body fluids, 61 tissue specimens and 16 abscesses. The sensitivity and specificity of Amplicor PCR compared to culture were 63.6% and 93.1% respectively. Analysis of 7 PCR-positive, culture-negative specimens confirmed that all were from patients with recently diagnosed tuberculosis under treatment. Eight specimens were PCR negative-culture positive, including a pleural fluid containing inhibitory substances. On acid-fast bacilli (AFB) smear-negative specimens, sensitivity and specificity were 53 and 100% respectively. The best results for Amplicor PCR were obtained with abscesses and biopsies. It is concluded that this test, highly specific for the diagnosis of tuberculosis, is at least as sensitive on extrapulmonary specimens as on smear-negative respiratory specimens.