Diagnosis of latent Mycobacterium tuberculosis infection: tuberculin test versus interferon-gamma release

Abstract: INTRODUCTION: The treatment of individuals with active tuberculosis (TB) and the identification and treatment of latent tuberculosis infection (LTBI) contacts are the two most important strategies for the control of TB. The objective of this study was compare the performance of tuberculin skin testing (TST) with QuantiFERON-TB Gold In TUBE(r) in the diagnosis of LTBI in contacts of patients with active TB. METHODS: Cross-sectional analytical study with 60 contacts of patients with active pulmonary TB. A blood sample of each contact was taken for interferon-gamma release assay (IGRA) and subsequently performed the TST. A receiver operating characteristic curve was generated to assess the cutoff points and the sensitivity, predictive values, and accuracy were calculated. The agreement between IGRA and TST results was evaluated by Kappa coefficient. RESULTS: Here, 67.9% sensitivity, 84.4% specificity, 79.1% PPV, 75% NPV, and 76.7% accuracy were observed for the 5mm cutoff point. The prevalence of LTBI determined by TST and IGRA was 40% and 46.7%, respectively. CONCLUSIONS: Both QuantiFERON-TB Gold In TUBE(r) and TST showed good performance in LTBI diagnosis. The creation of specific diagnostic methods is necessary for the diagnosis of LTBI with higher sensitivity and specificity, preferably with low cost and not require a return visit for reading because with early treatment of latent forms can prevent active TB.

摘要：
引言：活动性结核病（TB，Tuberculosis）患者的治疗，以及潜伏性结核感染（LTBI，Latent Tuberculosis Infection）接触者的筛查与治疗，是结核病防控的两大核心策略。本研究旨在比较结核菌素皮肤试验（TST，Tuberculin Skin Testing）与QuantiFERON-TB Gold In TUBE(r)在活动性肺结核患者接触者LTBI诊断中的应用性能。
方法：本研究为横断面分析研究，纳入60名活动性肺结核患者的接触者。采集每位接触者的血液样本进行干扰素γ释放试验（IGRA，Interferon-Gamma Release Assay），随后实施结核菌素皮肤试验。绘制受试者工作特征曲线（ROC曲线，Receiver Operating Characteristic Curve）以评估截断值，并计算灵敏度、预测值及诊断准确率。采用Kappa系数评估IGRA与TST结果的一致性。
结果：以5mm作为截断值时，结核菌素皮肤试验的灵敏度为67.9%、特异度为84.4%、阳性预测值（PPV，Positive Predictive Value）为79.1%、阴性预测值（NPV，Negative Predictive Value）为75%，诊断准确率为76.7%。经TST与IGRA检测的LTBI患病率分别为40%与46.7%。
结论：QuantiFERON-TB Gold In TUBE(r)与TST在LTBI诊断中均展现出良好的应用性能。开发兼具高灵敏度与高特异度的专用LTBI诊断方法十分必要，此类方法最好具备低成本且无需复诊判读结果的优势，因为对潜伏性结核感染者的早期治疗可有效预防活动性结核病的发生。