[Selection of the cutoff value on tuberculin skin test in diagnosing tuberculosis infection: a population-based cross-sectional study in Eastern China].

Objective: To confirm the cutoff induration diameter of tuberculin skin test (TST) so as to decrease the false positive of the TST. Methods: Fasting blood glucose test, TST and Quanti FERON-TB (QFT) Gold In-Tube test were administered to recruit participants at the baseline stage. QFT was used as the gold standard to determine the cutoff of the TST test. Results: Overall, 5 405 participants were enrolled in this study, of whom 1 104 (20.4%) were QFT positive. Among all the 5 405 participants that without stratification, diagnostic value reached the highest when the induration diameter was 10.25 mm with sensitivity and specificity as 0.731 and 0.727, respectively. When the participants were divided into groups as nondiabetics, confirmed diabetics, undiagnosed diabetics, the sensitivities and specificities appeared as 0.701, 0.837, 0.824 and 0.805, 0.821, 0.778 with induration diameters as 11.25 mm, 10.25 mm and 11.25 mm, respectively. Conclusions: Findings of this study confirmed that the specificity of tuberculin test could be significantly improved by using 10-12 mm as the cutoff value for diagnosing the latent tuberculosis infection.目的： 确定结核菌素试验的临界值来降低其诊断结核病潜伏性感染的假阳性。 方法： 测量受试者的FPG值，同时对受试者做结核菌素试验和QuantiFERON-TB（QFT）Gold In-Tube检测。以QFT为金标准，确定结核菌素试验（TST）试验的临界值。 结果： 共有5 405名参与者，其中1 104名（20.4%）QFT阳性。在5 405例患者中，PPD硬结直径为10.25 mm时诊断价值最高，其灵敏度为0.731，特异度为0.727。将受试者分为正常人、有糖尿病史患者、新确诊糖尿病患者，硬结直径分别在11.25 mm、10.25 mm和11.25 mm时诊断价值最高，其灵敏度和特异度分别为0.701、0.837、0.824和0.805、0.821、0.778。 结论： 本研究证实，以10~12 mm作为结核病潜伏性感染诊断的临界值可以大大提高结核菌素试验的特异性。.