Early Tuberculin Skin Test for the Diagnosis of Latent Tuberculosis Infection in Patients with Inflammatory Bowel Disease

Abstract

Background and aim: Sensitivity of tuberculin skin test [TST] during screening for latent tuberculosis infection [LTBI] is affected by steroid and/or immunosuppressant therapy. The aim of this study was to compare performance of the two-step TST in inflammatory bowel disease patients immediately before anti-tumour necrosis factor [TNF] therapy as part of routine screening for LTBI vs control patients when the TST was carried out at an early stage.

Methods: In this multicentre prospective controlled study, we evaluated the performance of two-step TST with 5-mm threshold. Factors associated with TST results were determined by logistic regression.

Results: We evaluated 243 candidates for anti-TNF therapy and 337 control patients. Overall, 105 patients [18.1%] had an induration ≥ 5 mm in the first TST or in TST retest. LTBI was diagnosed in 25% of patients by TST retest. Twenty-eight [11.5%] anti-TNF group patients vs 77 [22.8%] control patients had a positive TST (odds ratio [OR] 0.44, 95% confidence interval [CI] 0.28-0.70; P < 0.001]. In multivariate analysis, positive TST was associated with higher age [OR 2.63, 95% CI 1.21-5.72; P < 0.001] and 5-aminosalicylate therapy [OR 1.86, 95% CI 1.14-3.05; P = 0.013]. Negative TST was associated with steroid therapy [OR 0.36, 95% CI 0.16-0.83; P = 0.016], immunosuppressant therapy [OR 0.36, 95% CI 0.21-0.62; P < 0.001], or steroids + immunosuppressant therapy [OR 0.20, 95% CI 0.07-0.59; P = 0.004].

Conclusions: The sensitivity of routine TST performed just before starting anti-TNF therapy is low. TST performed at an early stage enables screening in the absence of immunosuppressive treatment and thus maximises the diagnostic yield of TST for detecting LTBI.

Keywords: Crohn′s disease; Tuberculosis; anti-TNF; immunosuppressant; inflammatory bowel disease; steroid; tuberculin skin test; ulcerative colitis.