Objectives: To investigate the risk factors for false-negative T-SPOT.TB results in patients with pulmonary TB (PTB) and extra-pulmonary TB (EPTB).
Methods: Patients with suspected TB who underwent valid T-SPOT.TB tests were prospectively enrolled at Beijing Chest Hospital between November 2012 and November 2013. Basic characters and clinical laboratory findings were compared between true-positive and false-negative T-SPOT.TB groups.
Results: Of 1928 suspected TB patients, 774 (530 PTB and 244 EPTB) microbiologically/histopathogenically-confirmed patients (636 culture-confirmed) were analyzed. Forty-six PTB patients (8.7%) and 32 EPTB patients (13.1%) had negative T-SPOT.TB results. Multivariate analysis showed that increased age [odds radio (OR) 2.26, 95% confidence interval (CI) 1.11-4.58], over-weight (BMI ≥ 25 kg/m(2), OR 2.43, 95% CI 1.05-5.63), and a longer period of illness before hospitalization (>6 months, OR 2.46, 95% CI 1.24-4.92) were independent risk factors for false-negative T-SPOT.TB results in PTB patients. In EPTB patients, increased age (OR 2.42, 95% CI 1.09-5.35) also showed an independent association with false-negative T-SPOT.TB results.
Conclusion: Careful interpretation of negative T-SPOT.TB results is necessary in older patients with suspected PTB or EPTB, and in PTB patients who are over-weight or have had longer periods of illness before hospitalization.
Keywords: Extra-pulmonary TB; False-negative; Pulmonary TB; Risk factor; T-SPOT.TB.
Copyright © 2015 The British Infection Association. Published by Elsevier Ltd. All rights reserved.