[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.