Diel R, Nienhaus A, Lange C, Meywald-Walter K, Forssbohm M, Schaberg T
School of Public Health, University of Düsseldorf, Germany.
Respir Res. 2006 May 17;7(1):77. doi: 10.1186/1465-9921-7-77.
BCG-vaccination can confound tuberculin skin test (TST) reactions in the diagnosis of latent tuberculosis infection.
We compared the TST with a Mycobacterium tuberculosis specific whole blood interferon-gamma assay (QuantiFERON-TB-Gold In Tube; QFT-G) during ongoing investigations among close contacts of sputum smear positive source cases in Hamburg, Germany.
During a 6-month period, 309 contacts (mean age 28.5 +/- 10.5 years) from a total of 15 source cases underwent both TST and QFT-G testing. Of those, 157 (50.8%) had received BCG vaccination and 84 (27.2%) had migrated to Germany from a total of 25 different high prevalence countries (i.e. >20 cases/100,000). For the TST, the positive response rate was 44.3% (137/309), whilst only 31 (10%) showed a positive QFT-G result. The overall agreement between the TST and the QFT-G was low (kappa = 0.2, with 95% CI 0.14.-0.23), and positive TST reactions were closely associated with prior BCG vaccination (OR 24.7; 95% CI 11.7-52.5). In contrast, there was good agreement between TST and QFT-G in non-vaccinated persons (kappa = 0.58, with 95% CI 0.4-0.68), increasing to 0.68 (95% CI 0.46-0.81), if a 10-mm cut off for the TST was used instead of the standard 5 mm recommended in Germany.
The QFT-G assay was unaffected by BCG vaccination status, unlike the TST. In close contacts who were BCG-vaccinated, the QFT-G assay appeared to be a more specific indicator of latent tuberculosis infection than the TST, and similarly sensitive in unvaccinated contacts. In BCG-vaccinated close contacts, measurement of IFN-gamma responses of lymphocytes stimulated with M. tuberculosis-specific antigen should be recommended as a basis for the decision on whether to perform subsequent chest X-ray examinations or to start treatment for latent tuberculosis infection.
卡介苗接种可能会干扰结核菌素皮肤试验（TST）在潜伏性结核感染诊断中的反应。
在德国汉堡对痰涂片阳性源病例的密切接触者进行的调查中，我们将TST与结核分枝杆菌特异性全血干扰素-γ检测（全血γ-干扰素释放试验；QFT-G）进行了比较。
在6个月期间，来自15例源病例的309名接触者（平均年龄28.5±10.5岁）接受了TST和QFT-G检测。其中，157人（50.8%）接种过卡介苗，84人（27.2%）从总共25个不同的高流行国家（即>20例/10万）移民到德国。对于TST，阳性反应率为44.3%（137/309），而只有31人（10%）QFT-G检测结果呈阳性。TST和QFT-G之间的总体一致性较低（kappa = 0.2，95%可信区间0.14 - 0.23），TST阳性反应与既往卡介苗接种密切相关（比值比24.7；95%可信区间11.7 - 52.5）。相比之下，未接种疫苗者中TST和QFT-G之间的一致性较好（kappa = 0.58，95%可信区间0.4 - 0.68），如果将TST的截断值设为10 mm而不是德国推荐的标准5 mm，则一致性提高到0.68（95%可信区间0.46 - 0.81）。
与TST不同，QFT-G检测不受卡介苗接种状态的影响。在接种过卡介苗的密切接触者中，QFT-G检测似乎是潜伏性结核感染比TST更具特异性的指标，在未接种疫苗的接触者中敏感性相似。对于接种过卡介苗的密切接触者，建议检测结核分枝杆菌特异性抗原刺激的淋巴细胞的干扰素-γ反应，作为决定是否进行后续胸部X线检查或开始潜伏性结核感染治疗的依据。
