Chest roentgenography is complementary to interferon-gamma release assay in latent tuberculosis infection screening of rheumatic patients

BACKGROUND: A study of latent tuberculosis infection (LTBI) burden by chest roentgenography (CXR) with reference to interferon-gamma release assay (IGRA) is still lacking in rheumatic patients of an intermediate tuberculosis burden area. METHODS: We retrospectively reviewed clinical data of patients with rheumatoid arthritis (RA), ankylosing spondylitis (AS), or psoriatic arthritis (PsA) receiving LTBI screening for biologics from Jan 2013 to April 2014. RESULTS: A total of 238 rheumatic patients who underwent LTBI screening were included in this study, of whom 46 (19.3%) had positive IGRA tests, 178 (74.8%) had negative results, and 14 (5.9%) had indeterminate results. Radiological findings suggesting healed tuberculosis (CXR-old-TB) were found in 18.1% of all patients, 23.9% in the IGRA -positive patients vs 16.9% in the IGRA-negative patients (OR 1.55 95% CI: 0.71–3.39, p = 0.27). Forty (40/46, 87.0%) IGRA-positive patients received isoniazid prophylaxis and 77.5% of them finished treatment. Six patients developed adverse effects of isoniazid treatment, resulting in an overall number needed to harm (NNH) of 6.7 (40/6). IGRA-non-positive patients with old TB-suggestive CXR comprised 13.4% (32/238) of all our rheumatic patients, and one of them developed pulmonary tuberculosis within one year after screening. CONCLUSIONS: LTBI disease burden in rheumatic patients is substantial according to the estimation of CXR and IGRA screening. Correlation between CXR and IGRA is not significant in rheumatic patients, which implies their complementary roles. IGRA-non-positive patients with old TB-suggestive CXR comprise a significant portion in rheumatic patients and merit cautious follow-up by rheumatologists, tuberculosis specialists, and pulmonologists.