Department of Clinical Science, Infection, Faculty of Medicine and Dentistry, University of Bergen ; Department of Microbiology, Haukeland University Hospital, Bergen, Norway ; St. John's Research Institute, Bangalore, Karnataka, India.
PLoS One. 2013 Sep 6;8(9):e71470. doi: 10.1371/journal.pone.0071470. eCollection 2013.
The utility of two-step tuberculin skin testing among adolescents in high tuberculosis prevalence settings is not well established.
To determine the proportion and determinants of a 0-4 mm response to an initial standard tuberculin skin test (TST) and evaluating 'boosting' with repeat testing.
Adolescents between 11 and 18 years attending schools/colleges underwent a TST; those with a response of between 0-4 mm had a repeat TST 1-4 weeks later.
Initial TST was done for 6608/6643 participants; 1257 (19%) developed a 0-4 mm response to the initial TST. Younger age and under-nutrition were more likely to be associated with a 0-4 mm response, while the presence of BCG (Bacillus Calmette Guerin) scar and higher socio-economic class were less likely to be associated with a 0-4 mm response. On repeat testing boosting was seen in 13.2% (145/1098; ≥ 6 mm over the initial test) while 4.3% showed boosting using a more conservative cutoff of a repeat TST ≥ 10 mm with an increment of at least 6 mm (47/1098). History of exposure to a tuberculosis (TB) case was associated with enhanced response.
The proportion of adolescents who demonstrated boosting on two-step TST testing in our study was relatively low. As a result repeat testing did not greatly alter the prevalence of TST positivity. However, the two-step TST helps identify individuals who can potentially boost their immune response to a second test, and thus, prevents them from being misclassified as those with newly acquired infection, or tuberculin converters. While two-step tuberculin skin testing may have a limited role in population- level TST surveys, it may be useful where serial tuberculin testing needs to be performed to distinguish those who show an enhanced response or boosters from those who indeed have a new infection, or converters.
两步法结核菌素皮肤试验在高结核流行地区青少年中的应用价值尚未得到充分证实。
确定初始标准结核菌素皮肤试验（TST）反应为 0-4 毫米的比例和决定因素，并评估重复检测的“增强”作用。
11 至 18 岁的青少年在校/院接受 TST；对初始 TST 反应在 0-4 毫米之间的人，在 1-4 周后重复 TST。
对 6608/6643 名参与者进行了初始 TST；1257 人（19%）对初始 TST 出现 0-4 毫米的反应。年龄较小和营养不良更容易与 0-4 毫米的反应相关，而卡介苗（BCG）瘢痕和较高的社会经济阶层与 0-4 毫米的反应不太相关。在重复测试中，增强反应见于 13.2%（145/1098；与初始测试相比≥6 毫米），而 4.3%（47/1098）使用重复 TST≥10 毫米且增量至少 6 毫米的更保守截止值显示增强反应。接触结核病（TB）病例的病史与增强反应相关。
在我们的研究中，两步 TST 检测显示增强反应的青少年比例相对较低。因此，重复检测并未显著改变 TST 阳性率。然而，两步 TST 有助于识别那些可以增强对第二次测试免疫反应的个体，从而防止他们被错误地归类为新获得感染或结核菌素转化者。虽然两步结核菌素皮肤试验在人群水平 TST 调查中可能作用有限，但在需要进行连续结核菌素检测以区分那些表现出增强反应或增强剂的人与确实存在新感染或转化者的情况下，它可能有用。
