Polymerase chain reaction in the diagnosis of tuberculosis

A rapid, sensitive, specific and yet economical method for the diagnosis ofM. tuberculosis and other mycobacteria in clinical specimen is a desperate and urgent requirement of the day in the laboratory diagnosis and hence management of tuberculosis. This need is further accentuated by emerging diseases like multi drug resistant tuberculosis, tuberculosis in AIDS patients and opportunistic mycobacterial infections, which do not respond to conventional anti TB therapy. Molecular methods, particularly PCR based detection ofM. tuberculosis, has come a long way since it was first described about fifteen years ago. Several probes have been developed and some of them, particularly the IS6110 and TB400 have been validated on several clinical samples. The latter has been validated on a variety of clinical specimens along with a simple sample processing method. Polymerase chain reaction based diagnosis ofM. tuberculosis has been introduced as one of the routine/confirmatory tests in clinical microbiology laboratory in some countries like Canada, the United States and the United Kingdom several years ago. The possibility of introducing PCR based direct diagnosis of drug resistance is being explored in some laboratories, particularly for drugs like rifampicin. The evolution and application of PCR for diagnosis ofM. tuberculosis is being analysed and discussed in this review.