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-TNF therapy as part of routine screening for LTBI versus control patients when the TST was carried out at an early stage.
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.
We evaluated 243 candidates for anti-TNF therapy and 337 control patients. Overall, 105 patients (18.1%) had an induration ?5 mm in first TST or in TST retest. LTBI was diagnosed in 25% of patients by TST retest. Twenty-eight (11.5%) anti-TNF group patients versus 77 (22.8%) control patients had a positive TST (odds ratio [OR] 0.44, 95% 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).
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 maximizes the diagnostic yield of TST for detecting LTBI.