Screening for Mycobacterium tuberculosis prior to anti-TNF therapy--an audit of impact of the British Thoracic Society guidelines on rheumatology practice in an area of low Mycobacterium tuberculosis prevalence

Abstract

SIR, Anti-TNF drugs have revolutionized rheumatology practice. However, a major concern is the propensity for patients taking these drugs to develop reactivation of latent Mycobacterium tuberculosis (MTB) infection. The British Thoracic Society (BTS) has provided guidelines [1] on risk assessment for TB prior to commencing anti-TNF treatment, but how relevant is it in areas of low MTB incidence? We examined the pre-treatment screening methods adopted at two UK hospitals situated in the East Anglia region, an area of low MTB prevalence, from August 2000 to August 2005 and applied the BTS guidelines retrospectively to patients otherwise screened in order to evaluate whether it would have had an impact on our clinical practice. Patients with RA prescribed an anti-TNF drug at the Norfolk and Norwich and Ipswich Hospitals NHS Trust were identified from a pre-existing database and case notes reviewed with regards to pre-treatment screening methods employed. This included a detailed clinical history and physical examination, tuberculin skin testing (Heaf test was done at Ipswich only) and a chest radiograph. We also examined in detail the records of patients diagnosed as having latent MTB at the time of screening to see if there were any subsequent cases of active MTB. Three hundred and thirty-nine patients were screened and 326 were started on anti-TNF therapy (121 etanercept, 46 adalimumab and 159 infliximab), 329 were Caucasian, 1 Asian British, 1 Chinese and 8 did not have their ethnicity recorded. Three hundred and nine patients (91%) were taking additional immunosuppressive medication. Eighty-one (24%) had tuberculin testing done (Ipswich ¼ 78, Norwich ¼ 3), 7 out of 81 tests (8.64%) were found to be Heaf Grade 3–4, 41 of 81 tests (51%) were negative. Six patients (1.7%) had a previous history of MTB or treatment for it, 238 of 339 (92%) had a chest radiograph done prior to treatment and 4 (1.2%) had an abnormal chest radiograph consistent with old MTB. Fifteen patients out of 339 (4.4%) were referred to a local TB specialist of which 10 (66%) were diagnosed as having latent TB. Six of 10 (60%) patients suspected as having latent TB started isoniazid chemoprophylaxis. Four chose not to have anti-TNF treatment. None of the patients were found to have active MTB at the time of screening and after a median follow-up time of 4.35 yrs no patients have had reactivation of MTB.