Winje Brita Askeland, Oftung Fredrik, Korsvold Gro Ellen, Mannsåker Turid, Ly Ingvild Nesthus, Harstad Ingunn, Dyrhol-Riise Anne Margarita, Heldal Einar
Division of Infectious Disease Control, Norwegian Institute of Public Health, 0403 Oslo, Norway.
BMC Infect Dis. 2008 Oct 17;8:140. doi: 10.1186/1471-2334-8-140.
In Norway, screening for tuberculosis infection by tuberculin skin test (TST) has been offered for several decades to all children in 9th grade of school, prior to BCG-vaccination. The incidence of tuberculosis in Norway is low and infection with M. tuberculosis is considered rare. QuantiFERONTB Gold (QFT) is a new and specific blood test for tuberculosis infection. So far, there have been few reports of QFT used in screening of predominantly unexposed, healthy, TST-positive children, including first and second generation immigrants. In order to evaluate the current TST screening and BCG-vaccination programme we aimed to (1) measure the prevalence of QFT positivity among TST positive children identified in the school based screening, and (2) measure the association between demographic and clinical risk factors for tuberculosis infection and QFT positivity.
This cross-sectional multi-centre study was conducted during the school year 2005-6 and the TST positive children were recruited from seven public hospitals covering rural and urban areas in Norway. Participation included a QFT test and a questionnaire regarding demographic and clinical risk factors for latent infection. All positive QFT results were confirmed by re-analysis of the same plasma sample. If the confirmatory test was negative the result was reported as non-conclusive and the participant was offered a new test.
Among 511 TST positive children only 9% (44) had a confirmed positive QFT result. QFT positivity was associated with larger TST induration, origin outside Western countries and known exposure to tuberculosis. Most children (79%) had TST reactions in the range of 6-14 mm; 5% of these were QFT positive. Discrepant results between the tests were common even for TST reactions above 15 mm, as only 22 % had a positive QFT.
The results support the assumption that factors other than tuberculosis infection are widely contributing to positive TST results in this group and indicate the improved specificity of QFT for latent tuberculosis. Our study suggests a very low prevalence of latent tuberculosis infection among 9th grade school children in Norway. The result will inform the discussion in Norway of the usefulness of the current TST screening and BCG-policy.
在挪威，几十年来，在卡介苗接种之前，一直对所有九年级学生进行结核菌素皮肤试验（TST）以筛查结核感染。挪威的结核病发病率较低，结核分枝杆菌感染被认为很少见。QuantiFERON-TB Gold（QFT）是一种用于结核感染的新型特异性血液检测方法。到目前为止，关于QFT用于筛查主要未接触过结核、健康的TST阳性儿童（包括第一代和第二代移民）的报道很少。为了评估当前的TST筛查和卡介苗接种计划，我们旨在（1）测量在学校筛查中确定的TST阳性儿童中QFT阳性的患病率，以及（2）测量结核感染的人口统计学和临床风险因素与QFT阳性之间的关联。
这项横断面多中心研究在2005 - 2006学年进行，TST阳性儿童从挪威农村和城市地区的七家公立医院招募。参与包括进行一次QFT检测和一份关于潜伏感染的人口统计学和临床风险因素的问卷。所有QFT阳性结果均通过对同一血浆样本的重新分析进行确认。如果确认试验为阴性，则结果报告为不确定，并为参与者提供新的检测。
在511名TST阳性儿童中，只有9%（44名）的QFT结果经确认呈阳性。QFT阳性与TST硬结更大、来自西方国家以外的地区以及已知接触过结核病有关。大多数儿童（79%）的TST反应在6 - 14毫米范围内；其中5%的儿童QFT呈阳性。即使对于TST反应超过15毫米的情况，两种检测结果之间的差异也很常见，因为只有22%的儿童QFT呈阳性。
结果支持这样一种假设，即除结核感染外的其他因素在很大程度上导致了该组儿童TST结果呈阳性，并表明QFT对潜伏性结核具有更高的特异性。我们的研究表明挪威九年级学生中潜伏性结核感染的患病率非常低。该结果将为挪威关于当前TST筛查和卡介苗政策的有用性的讨论提供参考。
