Reduced sensitivity of the QuantiFERON(®) test in diabetic patients with smear-negative tuberculosis.

SETTING:Immunosuppressive conditions have been associated with low sensitivity of interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST) for the diagnosis of tuberculosis (TB). However, no systematic analysis of patient and bacterial characteristics has been performed before. OBJECTIVE:To determine the sensitivity and the risk factors for false-negative QuantiFERON(®)-TB (QFT) assay and TST in TB patients. DESIGN:We performed a retrospective analysis of data collected in a community-based study of TB in San Francisco, CA, USA. We included 300 TB patients who underwent QFT and TST. RESULTS:The risk factors for false-negative QFT were human immunodeficiency virus infection and the use of QuantiFERON(®)-TB Gold. In patients with sputum smear-negative TB, diabetes mellitus (DM) was associated with false-negative QFT (OR 2.85, 95%CI 1.02-7.97, P = 0.045). TST sensitivity was higher than QFT sensitivity in DM patients (OR 9.46, 95%CI 2.53-35.3). CONCLUSIONS:In San Francisco, QFT sensitivity was lower than that of TST, especially in patients with DM. Stratified analysis by sputum smear results showed that this association was specific to smear-negative TB. In contrast, TST was not affected by the presence of DM.