Molecular Diagnostics for Tuberculosis
Molecular technology is now available to provide detection, identification, and antimicrobial sensitivity testing of mycobacteria. Ideally, a molecular probe would provide these functions directly in a clinical sample, with the sensitivity of a culture, but in a matter of hours rather than weeks. Such rapid results will be essential to provide optimal care for patients infected with M. tuberculosis or other mycobacterium species and to limit the spread of tuberculosis.
The FDA approved the Amplified Mycobacterium Tuberculosis Direct (AMTD) test (Gen-Probe, San Diego, California) in 1996. In various studies where the AFB (acid-fast bacilli) smears were cultured, the sensitivity of AMTD was 85.5% and its specificity was 100%. This test, which combines Gen-Probe’s transcription- mediated amplification and HPA technologies, yields results in 4-5 h. It can be used on patients who do not have cultivable M. tuberculosis but continue to shed these microorganisms. In addition, AMTD can aid in monitoring patients who have been treated with antitubercular drugs.