Transport of digested decontaminated sputum specimens to a central laboratory for testing for M. tuberculosis by Amplicor MTB test.

Rapid diagnosis of tuberculosis may improve management of infected patients and facilitate infection control procedures. The relatively slow growth rate of M. tuberculosis and the limited sensitivity and specificity of microscopy make rapid diagnosis difficult. Nucleic acid amplification techniques have been extensively studied for the detection of M. tuberculosis DNA and a number of commercial products for detection of M. tuberculosis nucleic acid in clinical specimens are now available. As performance of diagnostic PCR at central reference laboratories may be desirable, the impact of specimen transport on the performance of the Amplicor MTB PCR assay is of practical importance. We have assessed the performance of the Amplicor MTB PCR on specimens submitted and initially processed in laboratories in 3 cities and then transported to a single laboratory for PCR assay. The overall sensitivity of the PCR test was 97 per cent and the corrected specificity was 100 per cent. All of 23 culture positive specimens collected locally were PCR positive compared with 10 of 11 culture positive specimens transported from elsewhere. In this study transportation of digested decontaminated specimens to a central laboratory either frozen at -20 degrees, or overnight at room temperature had no apparent effect on the performance characteristic of the Amplicor MTB PCR assay.