Objective: To evaluate the T-SPOT. TB assay for the diagnosis of tuberculosis in a large clinical samples.
Methods: We analyzed the T-SPOT. TB results of 1 084 tuberculosis (TB) suspects who were admitted to the First Affiliated Hospital of Zhengzhou University from February 2011 to October 2011. The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio of T-SPOT. TB were analyzed according to the final diagnosis. Among these patients, 60 were retested by T-SPOT. TB after 2-4 week anti-tuberculosis treatment, and spot forming cells (SFCs) were compared before and after treatment. Paired t-test was used for comparison between groups.
Results: Three hundred and eighty-four patients were eventually diagnosed to have TB. Among 54 patients with laboratory diagnosis of TB, 42 were T-SPOT. TB positive, and the sensitivity was 77.8% (42/54). In 330 cases clinically diagnosed as tuberculosis, 289 were T-SPOT. TB positive, and the sensitivity was 87.6% (289/330). The total sensitivity of T-SPOT. TB was 86.2% (331/384). In 700 non-TB patients, 638 cases were T-SPOT. TB negative, and the specificity was 91.1% (638/700). The positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio were 84.2% (331/393), 92.3% (638/691), 9.69 and 0.15, respectively. Sixty patients were retested by the T-SPOT. TB after anti-TB treatment (2-4 weeks), and the results showed that both ESAT-6 and CFP-10 specific SFCs (47 and 18, respectively) decreased significantly compared with those before anti-TB treatment (99 and 49, respectively).
Conclusion: in this large scale study indicate that T-SPOT. TB is a promising test for the diagnosis of tuberculosis due to its high sensitivity and specificity.