Evaluation of (SD) MPT64 antigen rapid test, for fast and accurate identification of Mycobacterium tuberculosis...

To evaluate the SD MPT64 assay for rapid, preliminary identification of Mycobacterium tuberculosis complex (MTBC).

All specimens were processed using a standard methodology and inoculated into an automated liquid culture system (BD MGIT960). All signal positive cultures had a smear prepared and tested using a commercial molecular assay. From a carefully mixed MGIT960 vial, 100  μL of broth was loaded into the sample well, and the result recorded after 15 min. Repeat isolates from patients were excluded as were positive cultures contaminated with non-mycobacteria.

Fifty MTBC and 150 non-tuberculous mycobacteria were isolated during the study period. Test sensitivity was 98.04%, specificity (98.68%), positive predictive value (96.15%), and a negative predictive value (99.34%). There were two false positive results: Mycobacterium gastri and Mycobacterium fortuitum which were both identified by 16S rDNA and rpoB sequence analysis.

The SD MPT64 assay showed excellent performance. The major advantages are: (1) simplicity of test procedure, (2) rapid turnaround time, and (3) relatively inexpensive. When used in conjunction with the presence of serpentine cording in a stained smear from culture, a preliminary identification of MTBC may be made with high confidence.