Prevalence of LTBI in patients with autoimmune diseases and accuracy of IGRA in predicting TB relapse.

Objectives: The current study evaluated latent tuberculosis infection (LTBI) positivity in a cohort of Indian subjects and the accuracy of IFN-gamma release assay (IGRA) in predicting tuberculosis (TB) reactivation.

Methods: This cross-sectional, retrospective chart-based study considered patients diagnosed with autoimmune rheumatic diseases (AIRDs), especially those who received treatment with biologics or targeted synthetic (ts)DMARDs. The patients had undergone LTBI screening and IGRA test. The study excluded patients with inadequate information and those who had undergone test exclusively for diagnostic purpose. Statistical analyses were carried out for descriptive, demographic and clinical variables. Accuracy and error rate in predicting the absence of TB reactivation were calculated for IGRA test.

Results: The study selected 943 patients who had undergone IGRA pre-screening prior to the initiation of biologics or tsDMARDs with a mean age of 42.93 ± 14.01 years and male-to-female ratio of 1:2.08. RA was the most common primary diagnosis (43.16%). The proportion of subjects who received single, double and triple or more DMARDs or immune suppressants were 54.35%, 33.33% and 7.69%, respectively. Among the selected subjects, 125 patients were LTBI positive and 816 were negative. All patients, except one who tested positive at baseline, received antitubercular prophylaxis. Accuracy of IGRA in predicting the absence of TB reactivation was 99.6%, with an error rate of 0.46.

Conclusion: LTBI screening is beneficial in AIRDs patients prior to the prescription of biologics or tsDMARDs. IGRA is ideal for identifying patients with increased likelihood of developing TB upon receiving biologics or tsDMARDs with reasonable accuracy.