Accuracy of a new rapid antigen detection test for pulmonary tuberculosis

Tuberculosis (TB) is a major problem in the world. Treatment and control of TB needs detection of the Mycobacterium tuberculosis (MT) in the proper samples. While smear doesn't have enough sensitivity, culture and PCR are expensive, time consuming and unavailable in many centers. Recent development of a rapid TB antigen detection test (PrTBK) at Pasteur Institute of Iran could give a simple way for diagnosis of TB in about two hours. In this test the antigen-antibody complex will change color when gold conjugated mouse anti-rabbit antibody detects specific MT cell wall antigen in suspected samples.

We evaluated the diagnostic accuracy of PrTBK for diagnosis of pulmonary TB in comparison with smear, culture and PCR techniques in 56 consecutive samples (47 BAL and 13 sputum samples) obtained from patients with clinical suspicion of active TB.

Twentynine patients (52%) were female and seven patients were HIV positive. PrTBK was positive in 17 culture positive and 4 culture negative samples (100% sensitivity, 89% specificity and 92% accuracy in comparison with culture method). In two out of four patients with negative culture who were positive for PrTBK, PCR and anti-tuberculosis drugs trial therapy responses were in favor of tuberculosis. If we take this finding into account, the accuracy of PrTBK will rise.

High sensitivity and accuracy of PrTBK test enable us to initiate treatment on the basis of this convenient and rapid test.