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.