Department of Medicine, Section of Infectious diseases, Haukeland University Hospital, Bergen, N-5021, Norway.
BMC Infect Dis. 2010 Mar 8;10:57. doi: 10.1186/1471-2334-10-57.
Interferon-gamma (IFN-gamma) Release Assays (IGRA) are more specific than the tuberculosis skin test (TST) in the diagnosis of latent tuberculosis (TB) infection (LTBI). We present the performance of the QuantiFERON-TB Gold In-tube (QFT-TB) assay as diagnostic test and during follow-up of preventive TB therapy in outpatients from a TB low-endemic country.
481 persons with suspected TB infection were tested with QFT-TB. Thoracic X-ray and sputum samples were performed and a questionnaire concerning risk factors for TB was filled. Three months of isoniazid and rifampicin were given to patients with LTBI and QFT-TB tests were performed after three and 15 months.
The QFT-TB test was positive in 30.8% (148/481) of the total, in 66.9% (111/166) of persons with origin from a TB endemic country, in 71.4% (20/28) previously treated for TB and in 100% (15/15) of those diagnosed with active TB with no inconclusive results. The QFT-TB test was more frequently positive in those with TST > or = 15 mm (47.5%) compared to TST 11-14 mm (21.3%) and TST 6-10 mm (10.5%), (p < 0.001). Origin from a TB endemic country (OR 6.82, 95% CI 1.73-26.82), recent stay in a TB endemic country (OR 1.32, 95% CI 1.09-1.59), duration of TB exposure (OR 1.59, 95% CI 1.14-2.22) and previous TB disease (OR 11.60, 95% CI 2.02-66.73) were all independently associated with a positive QFT-TB test. After preventive therapy, 35/40 (87.5%) and 22/26 (84.6%) were still QFT-TB positive after three and 15 months, respectively. IFN-gamma responses were comparable at start (mean 6.13 IU/ml +/- SD 3.99) and after three months (mean 5.65 IU/ml +/- SD 3.66) and 15 months (mean 5.65 IU/ml +/- SD 4.14), (p > 0.05).
Only one third of those with suspected TB infection had a positive QFT-TB test. Recent immigration from TB endemic countries and long duration of exposure are risk factors for a positive QFT-TB test and these groups should be targeted through screening. Since most patients remained QFT-TB positive after therapy, the test should not be used to monitor the effect of preventive therapy. Prospective studies are needed in order to determine the usefulness of IGRA tests during therapy.
与结核菌素皮肤试验（TST）相比，γ干扰素释放试验（IGRA）在诊断潜伏性结核感染（LTBI）方面更为特异。我们介绍了 QuantiFERON-TB Gold In-tube（QFT-TB）检测在结核病低流行国家门诊患者中作为诊断试验和预防性抗结核治疗随访中的表现。
481 例疑似结核感染者接受 QFT-TB 检测。进行了胸部 X 射线和痰样本检查，并填写了一份关于结核危险因素的问卷。对 LTBI 患者给予 3 个月的异烟肼和利福平治疗，并在治疗后 3 个月和 15 个月进行 QFT-TB 检测。
QFT-TB 检测在 30.8%（481 例）的患者中呈阳性，在来自结核流行国家的患者中阳性率为 66.9%（111/166），在既往治疗过结核的患者中阳性率为 71.4%（20/28），在诊断为活动性结核的患者中阳性率为 100%（15/15），无不确定结果。与 TST 11-14 mm（21.3%）和 TST 6-10 mm（10.5%）相比，TST≥15 mm 的患者 QFT-TB 检测阳性率更高（47.5%）（p<0.001）。来自结核流行国家（OR 6.82，95%CI 1.73-26.82）、近期在结核流行国家逗留（OR 1.32，95%CI 1.09-1.59）、结核暴露时间（OR 1.59，95%CI 1.14-2.22）和既往结核病史（OR 11.60，95%CI 2.02-66.73）均与 QFT-TB 检测阳性相关。在预防性治疗后，35/40（87.5%）和 22/26（84.6%）在治疗后 3 个月和 15 个月时仍 QFT-TB 阳性。在开始治疗时（平均 6.13IU/ml ± 3.99SD）和治疗 3 个月（平均 5.65IU/ml ± 3.66SD）和 15 个月（平均 5.65IU/ml ± 4.14SD）时 IFN-γ 反应均相似（p>0.05）。
只有三分之一的疑似结核感染者 QFT-TB 检测阳性。近期移民来自结核流行国家和暴露时间长是 QFT-TB 检测阳性的危险因素，应通过筛查针对这些人群。由于大多数患者在治疗后仍 QFT-TB 阳性，因此不应使用该检测来监测预防性治疗的效果。需要前瞻性研究以确定 IGRA 检测在治疗期间的实用性。
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