Newer rapid diagnostic methods for tuberculosis: A preliminary experience.

ABSTRACT

Background:Present scenario of tuberculosis (TB) demands a reliable method for rapid diagnosis of TB. Several newer methodologies have been introduced over last 2 decades. However, clinical evaluation of all these methods is essential before bringing them into routine diagnostic practice. Aim: In the present study, we have evaluated 3 most promising methodologies viz. BACTEC 460 TB system (TB BACTEC), Transcription Mediated Amplification (TMA) and Phage assay for rapid detection of M. tuberculosis complex directly from respiratory and non-respiratory specimens. Material and Methods: Total 139 AFB smear positive and 41 AFB smear negative respiratory and non-respiratory specimens were tested by these methods and results were compared with conventional LJ method. Results and Conclusions: TMA is found to be most rapid and reliable method for detection of M. Tuberculosis complex from respiratory specimens with 93.8% sensitivity. However, for non-respiratory samples, TB BACTEC can be the method of choice. An average detection time for TB BACTEC is found to be 13 days and 15 days, compared to 31 days 35 days by LJ method in cases of smear positive respiratory and non-respiratory specimens respectively. Phage assay is highly specific for detecting M. tuberculosis complex and can be used as a rapid screening method for TB in cases of respiratory specimens collected from patients not receiving anti-TB therapy. As only viable TB bacilli are detected by phage assay, it can be used as a sensitive tool to monitor treatment success.