Use of interferon gamma release assays in clinical practice: review of QuantiFERON-TB prescription in a French university hospital.

Background: In recent years, the clinical use of interferon gamma release assays (IGRAs) has increased exponentially, while their indications remain controversial given difficulties in interpretation. Four indications were recommended by the French National Authority for Health (HAS) in 2006. We evaluated the utilization of the QuantiFERON-TB Gold In-Tube (QFT-IT) test over a 1-y period in a French university hospital and the impact of IGRA results in particular.

Methods: The QFT-IT tests requested in 2009 were analysed retrospectively, excluding those from the Occupational Health Department, the Regional Tuberculosis Centre, and rheumatology consultations for which the indications were clearly defined.

Results: Three hundred and sixty QFT-IT tests were analysed. The interpretation was frequently problematic given the inclusion of a significant proportion of patients over 80 y of age (11%), immunocompromised patients (43%), and patients with a known history of tuberculosis (6%). The indications failed to comply with HAS recommendations in 42% of cases (151/360), i.e. 14% of all QFT-IT tests in 2009. Thirty-seven percent of request forms were related to suspected pulmonary tuberculosis. In the case of a positive QFT-IT test, the clinical decision-making was changed in 58% of cases when the indications met the HAS recommendations, compared with only 16% if they did not (p < 0.005).

Conclusion: When the indications do not meet the health authority recommendations, the diagnostic value of the IGRA remains limited.