Diagnostic accuracy of Truenat in extrapulmonary tuberculosis

Diagnosing extrapulmonary tuberculosis (EPTB) remains a challenge even in today's era. Truenat, an indigenously developed nucleic acid amplification test (NAAT), has reported high sensitivity and specificity in sputum samples. However, its role in EPTB is still debatable.

To compare the efficacy of Truenat with other diagnostic modalities, like acid-fast bacilli (AFB) smear, mycobacterial culture, and a composite reference standard.

All patients suspected of EPTB were included in the study. The patients were evaluated based on a detailed clinical history, physical examination, and routine blood investigations. Specific samples from appropriate sites were collected and sent for Truenat, AFB smear, and liquid culture, and the results were compared. Statistical analysis was performed using SPSS Strata 19.0.

We included a total of 235 patients with a male:female ratio 1.9:1. Pleural effusion was the most common form of EPTB. The smear positivity was 16.6%. The Truenat positivity was 45.1%, with the highest in pus (56.5%), followed by lymphnode (67.80%) and pleural fluid (41.5%). The culture positivity was 34.9%. In comparison to AFB smear, the overall sensitivity and specificity of Truenat were 100% and 65.82%, respectively; the positive predictive value was 36.79%, while the negative predictive value was 100%. Comparing Truenat with culture revealed a sensitivity, specificity, positive predictive value, and negative predictive value of 79.27%, 73.2%, 61.32%, and 86.82%, respectively.

Truenat carries a high sensitivity and specificity for most EPTB samples in our study. A larger-scale study with a larger and uniform number of samples is recommended for more appropriate results.