Anti–tumor necrosis factor α drugs are known to reactivate latent tuberculosis (TB). Current guidelines recommend screening for latent tuberculosis infection, with either tuberculin skin test (TST) or interferon gamma release assays such as QuantiFERON-TB Gold (QFT-G). Given the high rates of anergy to TST among immunosuppressed inflammatory bowel disease (IBD) patients, there is considerable interest in evaluating the superiority of interferon gamma release assays over TST in this patient population to diagnose latent tuberculosis infection. We compared the performance of TST and QFT-G for screening latent TB among immunosuppressed IBD patients based on prevalence, mortality risk from reactivation TB, and costs.
A decision analytical model was constructed to compare 1-year outcomes and costs of using TST or interferon gamma release assay in an immunosuppressed IBD population.
Under the base case scenario, for every 1000 patients screened, the QFT-G strategy resulted in 0.53 deaths from reactivation TB compared with 1.92 deaths using TST. The QFT-G strategy results in 1.85 reactivation TB versus 6.7 reactivation TB using TST. The model was not sensitive to background prevalence of latent TB. The cost of QFT-G would have to be more than double for the TST strategy to become more cost effective. QFT-G also remains the cost-effective option unless the sensitivity of the TST improves by 400%.
Under a broad range of parameter values, the QFT-G strategy dominates the TST strategy in cost-effectiveness. Consideration should be given to QFT-G as the preferred method of identifying latent TB in all immunosuppressed IBD patients.