A retrospective study of the indications for the use of interferon gamma release assays (IGRA) in a United Kingdom (UK) district general hospital (DGH) tuberculosis (TB) clinic

Background: Interferon gamma release assay (IGRA) is a relatively new investigation for the diagnosis of latent TB. After initial interest in this test for diagnosis of active TB, NICE recommends the use of IGRA in the diagnosis of latent TB only, as set out by guidance in 2010. Aim: This study was to audit the number of tests done since the introduction of IGRAs to the DGH in 2011 and whether they were being used in accordance with NICE guidance. Method: Retrospective review of the electronic hospital records for patients who had IGRA tested between April 2011 and December 2011. The reason for the test was categorised into: diagnosing active TB, contact tracing, pre biological therapy, new entrant screening or other. The result of the test; tuberculin skin test (TST) prior to IGRA and result; and any treatment given for TB was recorded. Results: 260 tests were done, 13 were excluded. Conclusion: Our study found that IGRAs were being used for diagnosing active TB in spite of national guidelines not recommending it. The indication for the additional use of TST in those having IGRA was inconsistent. Algorithmic guidelines for the use of IGRA, as well as TST prior to IGRA need to be adopted in local hospitals to ensure proper use of resources.