Supplementary Diagnostic Value Of T-SPOT.TB For Active Tuberculosis And Clinical Characteristics

Objectives:The aim of this study is to explore the supplementary value of T-SPOT.TB in the diagnosis of active tuberculosis and its clinical characteristics,analyze risk factors of false-positive and false-negative for T-SPOT.TB,and to figure out the relationship between T-SPOT.TB and chest CT.Methods:This is a retrospective analysis of 1193 inpatients selected from the department of Pulmonary and Critical Care Medicine,Ruijin hospital Shanghai Jiao Tong University School of Medicine from April 2015 to March 2018.All of the included patients had been detected by peripheral blood T-SPOT.TB and are divided into two groups:active tuberculosis group and non-active tuberculosis group.Their demographic information,underlying diseases,personal history and laboratory tests were collected.Symptoms and imaging characteristics of active TB patients were recorded simultaneously.We calculated the different diagnostic efficiency at different cutoffs,and analyzed the factors relevant to the level of T-SPOT.TB.Results:A total of 114 ATB patients and 1079 non-ATB patients were included in this study,and ATB patients had higher level of T-SPOT.TB than non-ATB group.Sensitivity and specificity of T-SPOT.TB for diagnosing active TB are 78.95%and 68.58%,with PPV of 20.98%and NPV of 96.86%.With the increase of the cutoff point,both the specificity and PPV were significantly increased.In the diagnostic accordance rate curves,ESAT-6,CFP-10,and max(ESAT-6 or CFP-10)achieved stationary phase at 40 sfu,while min(ESAT-6 and CFP-10)achieved stationary phase at 20 sfu,sum(ESAT-6 and CFP-10)achieved stationary phase at 70 sfu,reaching 90.28%,90.28%,90.36%,89.44%and 90.78%respectively.Multiple logistic regression analysis show that TB history(p=0.001),tobacco use(p=0.005),diabetes(p=0.035)and old age(p=0.031),are risk factors leading to false-positive result for T-SPOT.TB.Among ATB patients,the number of T-SPOT.TB in symptomatic patients was relatively higher than that in asymptomatic patients(p=0.060).On chest CT of pulmonary tuberculosis,T-SPOT.TB had no significant relationship with the number of pulmonary lobes involved(p=0.965)and the maximum measurable lesion size(p=0.742).Regression analysis suggested that with thin-wall cavity or not was the only character related to the level of T-SPOT.TB(OR 0.153,95%CI 0.030-0.786,p=0.025).Conclusion:T-SPOT.TB is not only a diagnostic tool for LTBI,but also play an auxiliary role in diagnosing ATB.ATB and non-ATB can be better differentiated when defining cutoff point at 40 sfu of EAST-6/CFP-10 or at 20 sfu of ESAT-6 and CFP-10 or at 70 sfu of ESAT-6+CFP-10.TB history,tobacco use,DM and old age,are the five risk factors leading to false-positive result for T-SPOT.TB.On chest CT scan,the level of T-SPOT.TB is relevant to if thin-walled cavity is existed.