Diagnostic yield of fast plaque TB test for rapid detection of Mycobacterium in tuberculosis suspects

To compare the diagnostic yield of FAST Plaque TB test with the conventional methods for detection of mycobacterium tuberculosis in sputum of Tuberculosis suspects at Jinnah Postgraduate Medical Center Karachi Pakistan.

A comparative study of diagnostic yield of FAST Plaque TB test with the culture and ZN staining, conducted from January to June 2004.

The study was completed on 48 samples, 31 (64.58%) male and 17 females (35.42%). Half of the cases were sputum positive. Culture positive was in 17 (35.41%) and negative in 28 (58.3%) wereas 3 (6.25%) were contaminated. FAST Plaque TB test was positive in 16 (33.33%) and negative in 32 (66.6%) specimens. Out of 17 culture positive, 2 (11.7%) were negative and in 28 culture negative, 1 (3.57%) specimen was positive for FAST Plaque TB test. Out of 24 smear positive, 11 (45.83%) were negative and in 24 smear negative, 3 (12.5%) were positive, for FAST Plaque TB test. Compared to culture it has sensitivity of 86.23% and specificity of 96.42%, positive predictive value of 93.75% and negative predictive value of 93.1%.

FAST Plaque TB test is a simple test that can detect viable mycobacterium in 2 days. It has a good sensitivity and specificity. The cost is three times less than the other available tests like PCR. Thus it can be useful in the diagnosis of tuberculosis as an adjunct to sputum microscopy in endemic countries.