The Application Of T-SPOT.TB In The Diagnosis Of Active Tuberculosis

Background:China has a high incidence of tuberculosis. Tuberculosis is one of the most infectious disease threaten human health. Traditional diagnostic techniques, such as tuberculosis Sputum Smear and TST tests, lack sensitivity and specificity. In recent years, the T-SPOT.TB test, base on antigen-specific T cell response, has been developed as a new method for tuberculosis diagnosis. However,large-scale evaluation of this new method for diagnosing active tuberculosis has not been reported in TB high burden countries.Method and objective:This retrospective study was conducted at the Department of Respiratory Medicine and Infectious Diseases of the First Affiliated Hospital of Zhejiang University, and includes273patients with suspected active tuberculosis infection admitted to the hospital between January2012to June2012. We assessed the value of peripheral blood T-SPOT.TB assay for the diagnosis of active tuberculosis by comparing T-SPOT.TB test results and final clinical diagnosis in routine clinical practice, as well as, evaluate the clinical value of T-SPOT. TB, Sputum smear and TST for the diagnosis of tuberculosis. Result:116cases (42.49%) patients had a final diagnosis of active tuberculosis.101cases of active tuberculosis had a positive T-SPOT.TB result. Sensitivity of T-SPOT.TB for active tuberculosis was87.07%. Out of the144cases where active tuberculosis was excluded from diagnosis,115of these patients produced negative T-SPOT.TB results. Specificity was79.86%, positive predictive value was77.69%, negative predictive value was88.46%, positive likelihood ratio was4.32, and negative likelihood ratio was0.16. There were91cases of pulmonary tuberculosis patients, including78cases that had a positive T-SPOT.TB result.The sensitivity was85.71%. There were25cases of extra pulmonary tuberculosis, including23cases with positive T-SPOT.TB result. The sensitivity was92%. Extra pulmonary tuberculosis had a higher sensitivity than pulmonary tuberculosis in the T-SPOT.TB test, which was statistically significant. The sensitivity of acid-fast bacillus test of sputum smear was32.97%, specificity was99.04%, positive predictive value96.77%, negative predictive value of62.80%. The sensitivity of TST test was55.17%, specificity was72.22%, positive predictive value61.54%, negative predictive value of66.67%. Among the three methods, the sensitivity of T-SPOT.TB was the highest, and the sensitivity of Sputum Smear was the lowest. T-SPOT.TB can greatly reduce the rate of missing inspection of tuberculosis, therefore it can be used as an effective and assistant method for rapid diagnosis of tuberculosis.Conclusion:The study shows that T-SPOT.TB detection had a high sensitivity, provided a favorable evidence for clinical diagnosis. T-SPOT.TB detection had a higher negative predictive value, can help rule out the diagnosis of active tuberculosis. The T-SPOT.TB detection had a higher sensitivity in extrapulmonary tuberculosis, so the diagnosis in extrapulmonary tuberculosis became much easier. But T-SPOT.TB detection has the shortcoming of false positive and high cost, which limited the promotion in less developed regions.