关键词: 接触者追踪, 危险因素, 实验室技术和方法, 潜伏性结核病, 多相筛查

Abstract:

Objective Evaluate the value of tuberculin skin test (TST) and interferon-gamma release assay test (IGRA) in screening latent tuberculosis infection (LTBI) among children with different risk levels.Methods Collection of information on 965 children with a history of contact with active tuberculosis (ATB) patients enrolled at Beijing Children’s Hospital from 2013 to 2015, excluding 451 children diagnosed by etiology or clinically as ATB and 31 children diagnosed as inactive tuberculosis based on medical history and imaging examination, 483 children were finally included for the study and analysis of LTBI screening by TST and IGRA. Close contact history, children aged <5 years and no BCG scar were defined as risk factors, and the risk level was classified according to the number of risk factors. Those without the above risk factors were grouped as Grade Ⅰ (218 cases), those with 1, 2 and 3 risk factors were grouped as Ⅱ (210 cases), Ⅲ (54 cases) and Ⅳ (1 case, incorporate Ⅲ), respectively. Chi-square test was used to analyze the positive rates of TST and IGRA, and the univariate analysis related to positive results was conducted, P<0.05 was considered to be statistically significant. Kappa test was used for consistency analysis of the two laboratory techniques.Results All of the 483 children were tested by IGRA, the positive rate was 2.48% (12/483). The positive rates of IGRA in the Ⅰ-Ⅲ group were 2.29% (5/218), 2.38% (5/210), and 3.64% (2/55), respectively, and the difference was not statistically significant (χ ²=0.459, P=0.795). TST was performed in 369 children, the positive rate was 11.38% (42/369), and the positive rates of TST in the Ⅰ-Ⅲ group were 9.36% (16/171), 12.74% (20/157) and 14.63% (6/41), the difference was not statistically significant (χ ²=1.412,P=0.494). The combined detection of the two methods (TST+IGRA) means that the positive rate of either method was 9.11% (44/483), and the positive rates of TST+IGRA in the Ⅰ-Ⅲ group were 7.34% (16/218), 9.52% (20/210), 14.55% (8/55), and the difference was not statistically significant (χ ²=2.832,P=0.243). The positive rates of the three screening methods were statistically significant in the risk grades Ⅰ and Ⅱ (χ ²=7.861,P=0.020;χ ²=13.318,P=0.001). The close contact history with tuberculosis patients had the most significant correlation with the positive results of TST and IGRA. The positive rate of TST (25.26%, 24/95) or IGRA (5.00%, 6/120) in children with close contact with ATB patients was higher than that in non-intimate patients (6.57% (18/274), 1.65% (6/363)), the difference was statistically significant (χ ²=21.131,P=0.000, OR (95%CI)=4.329(2.232-8.396); χ ²=4.291,P=0.038,OR (95%CI)=3.186(1.006-10.096)).The consistency of the two tests was poor and the Kappa value was 0.346.Conclusion Among children with history of exposure to tuberculosis, those at the higher risk levels have the higher risk to develop LTBI, which is a high risk factor for LTBI in children. Due to the poor consistency of the two tests, in order to avoid missed diagnosis, combination use of TST and IGRA for screening LTBI in high-risk children is recommended.

Key words: Contact tracing, Risk factors, Laboratory techniques and procedures, Latent tuberculosis, Multiphasic screening