Targeted Screening for Latent TB Infection prior to Biologic Therapy to Improve Patient Safety and Reduce Costs: A Prospective Observational Study

Objective. Our current practice of screening for latent TB infection (LTBI) using universal T-SPOT assays is not in line with British Thoracic Society (BTS) recommendations. We set out to determine the clinical benefit and cost effectiveness of blanket TSPOT.TB (T-SPOT) testing as a screening tool for patients awaiting anti-TNF-α therapy. Methods. 130 consecutive rheumatology patients were investigated for LTBI before commencing anti-TNFα therapy at Gartnavel General Hospital, Glasgow, an area of low TB prevalence and high BCG vaccination. Chest radiograph and clinical interview were used to identify risk factors for LTBI. The annual risk of TB was calculated using tables from BTS recommendations and then compared to the risk of drug-induced hepatitis. All patients were given a T-SPOT according to current local policy. Indeterminate T-SPOTs were recorded and repeated. Results. For 130 patients, a total of 160 tests were required resulting in a cost of £24,000. 99 (76%) patients had no TB risk factors and a total of 22 repeat tests were required before returning negative results. This equates 121 T-SPOTs and potential cost savings of £18,150. Conclusion. In the absence of risk factors for TB and an abnormal chest radiograph, the use of T-SPOT as a first line test for LTBI may result in unnecessary risk of TB chemoprophylaxis-induced hepatitis, increased costs, and a delay in early anti-TNFα therapy.