Diagnostic accuracy of urine lipoarabinomannan in presumptive TB patients in South India - A cross-sectional study.

BACKGROUND

Tuberculosis (TB) remains a major global health challenge, particularly in developing countries. Non-sputum diagnostic tools are the need of the hour for effective TB diagnosis, especially in paucibacillary and extrapulmonary cases. This study evaluated the diagnostic accuracy of urine lipoarabinomannan (LAM) in presumptive TB patients in South India.

MATERIALS AND

METHODS

The cross-sectional study, with a sample size of 94, was conducted between May 2022 and November 2023 in a tertiary teaching institute. Urine LAM was detected using ELISA, and results were compared with MGIT liquid culture, GeneXpert, and AFB smear. Chest X-ray scores were assessed using the Timika system. Diagnostic accuracy (sensitivity, specificity, PPV, NPV) and associations with disease severity (AFB smear grades, CXR scores) were analyzed.

RESULTS

Urine LAM showed a sensitivity of 97.7 % and specificity of 38 % compared to MGIT liquid culture. In confirmed TB cases (microbiologically and clinically diagnosed), sensitivity and specificity were 94.5 % and 80 %, respectively. Urine LAM outperformed AFB smear (61.36 % sensitivity) and GeneXpert (88.6 % sensitivity). In extrapulmonary TB, urine LAM demonstrated 100 % sensitivity and NPV. Higher urine LAM levels correlated significantly with higher AFB smear grades (p < 0.05).

CONCLUSION

Urine LAM ELISA demonstrated high sensitivity and NPV, making it a valuable screening test for TB, particularly in paucibacillary and extrapulmonary cases. Its association with higher AFB smear grades and chest X-ray scores suggests potential for assessing disease severity and treatment response. Further research using next-generation assays is needed to validate its diagnostic performance and suitability for point-of-care use.