Patients with rheumatic diseases are at higher risk of developing tuberculosis (TB). The objective of this prospective study was to evaluate the T-SPOT.TB assay (T cell enzyme-linked immuno-spot assay), for the diagnosis of tuberculosis infection in rheumatic disease patients in China.
Prospectively enrolled patients came from the Department of Rheumatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine between July 2008 and Aug 2012 for TB screening. Subjects' histories of TB infection, previous TB contact or bacille Calmette-Guérin vaccination and concurrent immunosuppressive therapy, were reviewed carefully and recorded in detail. TST (tuberculin skin test) and TSPOT.TB assay were performed on the subjects. A prospective evaluation by Chi-square test was used for sensitivity and specificity of both TST and T-SPOT assay.
A total of 311 subjects included 114 (36.66%) male and 197 (63.34%) female subjects, with a median age of 37.7 ± 12.6 years (range 17-72). Thirty-two patients (10.29%) had a history of TB infection or previous TB contact; 256 patients (82.32%) were using glucocorticoids or immunosuppressants; 28 patients (9.0%) were clinically diagnosed as having TB infection. The sensitivity and specificity of TST for TB screening in rheumatic disease patients was 81.82% (9/11) and 67% (67/100), respectively. However, the sensitivity and specificity of T-SPOT assay was statistically higher at 92.86% (26/28) and 93.64% (265/283), respectively (P < 0.05).
As a new immunoassay for TB diagnosis, the sensitivity and specificity of T-SPOT is higher than TST. It is of great importance in the diagnosis of active or latent TB infection in rheumatic disease patients.