DETECTION AND IDENTIFICATION OF MYCOBACTERIUM-TUBERCULOSIS DIRECTLY FROM SPUTUM SEDIMENTS BY AMPLICOR PCR

Sputum specimens received for the diagnosis of tuberculosis or other m ycobacterial infections were tested by a PCR-based assay and culture t echniques, Results of the PCR assay (Amplicor Mycobacterium tuberculos is Test) were compared with results of standard culture techniques wit h cultures held for 6 weeks. One thousand nine specimens were included : 301 retrospective specimens (frozen at -70 degrees C and later teste d by PCR) and 708 prospective specimens (tested within 1 day of proces sing). One hundred sixty-two (16%) of the specimens were culture posit ive for M, tuberculosis; 83 (51%) of these were also fluorochrome stai n positive. The sensitivity and specificity of the Amplicor PCR compar ed with those of culture were 83% (134 of 162 specimens) and 97% (800 of 827 specimens), respectively. The sensitivity for fluorochrome stai n-positive specimens was 99%, and that for fluorochrome stain-negative specimens was 66%. The great majority of the 28 PCR-negative, culture -positive specimens were low positives; 27 were smear negative and 19 contained <100 CFU of M. tuberculosis per ml. The 27 PCR-positive; cul ture-negative specimens included 24 that were positive by repeat testi ng by alternate primer PCR and were from patients with tuberculosis On antimicrobial therapy. With these considered culture misses, the fina l sensitivities of PCR and culture were 85, and 87%, respectively, Whi le the specificities were 99.6 and 100%, respectively. After normal la boratory processing of sputum specimens, the Amplicor PCR assay can be completed in 8 h, Thus, it is possible to have results available with in 10 h of specimen submission.