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Objective To evaluate the diagnostic value of interferon-gamma release assays (IGRAs) for detecting active tuberculosis (TB) in previously Bacillus Calmette-Guerin (BCG)-vaccinated patients.Methods 540 patients underwent the T-SPOT.TB test including 295 active pulmonary TB (PTB),52 active extrapulmonary TB (EPTB),11 inactive TB and 182 non-TB cases.At the same time,186 active tuberculosis (ATB) (including PTB and EPTB) patients and 125 non-TB patients underwent also tuberculin skin tests (TST).Correlations between the sensitivity of T-SPOT.TB assays and lung lesion severity,positive smear grade,disease site and the durations of anti-TB treatments were evaluated.Results The sensitivity and specificity of the T-SPOT.TB assay for active TB diagnosis were 76.66% and 76.37% and the positive rate in inactive TB test results was significantly lower (23.63%) (P =0.00).The sensitivity was higher in PTB cases than that in EPTB cases (P =0.01).The sensitivity in active TB cases during anti-TB treatment was significantly lower than without treatment (P =0.002) and the sensitivity gradually decreased with the treatment durations (P =0.01).In addition we found a statistically significant specificity difference between the T-SPOT.TB and TST results (76.37% vs.51.15%,P=0.000),whereas the sensitivities did not differ (76.66% vs.75.56%) Conclusion The T-SPOT.TB assay is a promising test for active PTB diagnosis in a BCG vaccinated population and should replace TST.As treatments lead to less sensitivity of the test,the T-SPOT.TB assay might also be suitable for treatment outcome estimations.