Epidemiology of Latent Tuberculosis in Rheumatic Immune-Mediated Inflammatory Diseases—Study of 1117 Patients and Descriptive Literature Review

<b>Background/Objectives:</b> Patients with rheumatic immune-mediated diseases (rheumatic-IMID) and latent tuberculosis (LTBI) are at an increased risk of developing active tuberculosis (TB); therefore, screening is recommended before starting biological treatment. The aims of this study were as follows: (i) to assess the prevalence of LTBI, (ii) to determine the importance of using a booster test in TST-negative patients, (iii) to compare the tuberculin skin test (TST) with the interferon-gamma release assay (IGRA), (iv) to perform a review of the prevalence of LTBI. <b>Methods:</b> A cross-sectional hospital study was performed, including patients diagnosed with rheumatic-IMID who underwent a TST and/or IGRA during the period 2016-2020. If the first TST was negative, a new TST (booster) was performed. <b>Results:</b> A total of 1117 patients were included. The overall prevalence of LTBI was estimated to be 31.7% (95% confidence interval, 29.74-33.66). The LTBI prevalence ranged from 38.5% for vasculitis to 14% for sarcoidosis. The booster test was positive in 22.9% of 817 patients with a negative or indeterminate IGRA. The IGRA was positive in 3.8% of 793 patients with a negative booster.The adjusted Cohen's kappa coefficient between TST (+booster) and IGRA was 0.62. <b>Conclusions:</b> LTBI is frequent in patients with rheumatic-IMID. IGRA and TST (+booster) show a moderate, fair grade of agreement. Therefore, performing both tests before biological therapy should be highly recommended.