DIAGNOSIS OF MYCOBACTERIAL INFECTIONS BY NUCLEIC-ACID AMPLIFICATION -18-MONTH PROSPECTIVE-STUDY

We have investigated the use of DNA amplification by PCR for the detec tion of mycobacteria in clinical specimens, with the gene encoding the 16S rRNA as a target. Following generic amplification of mycobacteria l nucleic acids, screening was done with genus-specific probe; this wa s followed by species differentiation by use of highly discriminating probes or nucleic acid sequencing. In a prospective 18-month evaluatio n, criteria to select specimens for PCR analysis were defined. Of a to tal of 8,272 specimens received, 729 samples satisfied the criteria an d were subjected to DNA amplification. Clinical specimens included mat erial from the respiratory tract (sputa and bronchial washings), aspir ates, biopsies, and various body fluids (cerebrospinal, pleural, perit oneal, and gastric fluids). After resolution of discrepant results, th e sensitivity of the PCR assay was 84.5%, the specificity was 99.5%, t he positive predictive value was 97.6%, and the negative predictive va lue was 96.4%. The sensitivity and negative predictive value of cultur e (with a combination of broth and solid media) were 77.5 and 94.8%, r espectively. In conclusion, this PCR assay provides an efficient strat egy to detect and identify multiple mycobacterial species and performs well in comparison with culture.