Factors Contributing to False-Negative Enzyme-Linked Immunospot Assay for Interferon-Gamma Results in Active Tuberculosis

Background: The enzyme-linked immunospot assay test (T-SPOT.TB) is effective for detecting TB, but there are still some persons with tuberculosis (TB) who have negative results. The aim of this study was to analyze the factors that contribute to false negative results in active TB patients. Methods: We investigated the clinical trial and laboratory data of the active TB patients hospitalized in the First Affiliated Hospital of Xi'an Jiaotong University from May 2013 to November 2014. Results: In 556 active TB patients, 198 infected sites were pulmonary, 358 infected sites were extra pulmonary, and 13.85% (77/556) had false negative T SPOT.TB results. The univariate and multivariate analysis showed that age and bone/joint TB were the factors contributing to the T-SPOT. TB false negative results and pleural TB were related to true positive results. Conclusions: The site of TB may significantly affect the sensitivity of T-SPOT.TB. False negative results of TSPOT.TB are associated with older age and bone/joint TB, so in older adult patients or those with bone/joint TB, the exclusion of TB should be regarded with caution when T-SPOT.TB results are negative.