Figure 1.

 Algorithm to indicate the approach to prevention of tuberculosis (TB) in patients on immunosuppressants who need infliximab or other anti-tumour necrosis factor (TNF)-α therapy for Crohn’s disease. The high incidence of anergy in patients with Crohn’s disease who take immunosuppressants^14,15 makes tuberculin skin testing unreliable and unnecessary. The decision about TB chemoprophylaxis in individual patients with no history of TB and a normal chest x ray (CXR) is dependent on a comparison of their ethnicity related risk of acquiring TB during anti-TNF therapy and the risk of drug induced hepatitis during chemoprophylaxis (see text and British Thoracic Society¹). (For recommendations about the prevention of TB in the small minority of patients with Crohn’s disease not taking concomitant immunosuppressive therapy, and in those with ulcerative colitis in whom infliximab is being considered, see British Thoracic Society¹).