Evaluation of three immunological tests for the diagnosis of pulmonary tuberculosis in a rural endemic area of Bangladesh

Abstract

Objective: Bangladesh is a high tuberculosis burden country. It is always challenging to diagnose active pulmonary tuberculosis (PTB) cases in rural areas where the setting up of conventional microscopic and cultural diagnostic tools is difficult. The objective of the present study is to find a feasible, reliable and easily accessible alternative diagnostic approach for PTB in the rural areas of Bangladesh. Methods: A total of 86 sputum samples were collected from clinically suspected PTB patients of Anantapur village, an underdeveloped remote area of Netrokona district, Bangladesh. Sputum samples were screened by Ziehl-Neelsen (Z-N) and fluorescence staining methods and were categorized as smear-positive active PTB cases (n= 50) and smear-negative controls (n= 36); then the performance of three popular immunological tests were evaluated, including ICT, ELISA and Mantoux tests (MT). Results: The sensitivity of ICT, ELISA, and MT (10. mm induration size) was 68%, 84% and 96%, respectively, and the specificity of these tests was 94.4%, 80.6% and 52.8%, respectively. When the cut-off size of induration in MT was changed from 10 to ≥15. mm, the sensitivity and specificity of MT became 92% and 83.3%, respectively. It was also found that the interpretation of MT was not significantly affected by BCG vaccination when ≥15. mm induration was taken as a cut-off value. Conclusion: Considering the resource-constraints of rural and remote areas, the Mantoux test could be an alternative tool for the diagnosis of active PTB.