研究背景：目前針對高危險結核感染群的篩檢方式包括：結核菌素皮膚試驗（Tuberculin Skin Test, TST試驗）、痰液抗酸性染色法（Acid-Fast Bacilli, AFB）、與全血丙型干擾素檢驗（Interferon-gamma release assays, IGRAs）三種；然TST試驗則較易受卡介苗（Bacille Calmette-Guérin, BCG）影響而產生偽陽性，不適用於政策上有推行施打BCG的國家；AFB檢驗則有非專一性之疑慮，而IGRAs檢驗檢驗經研究證實該檢驗方法中的特異性抗原在偵測結核菌感染上並不會因施打BCG而受到影響。

研究目的：本研究想了解IGRAs檢驗在檢測結核病患上之精確度指標，並探討該檢測丙型干擾素（Interferon-Gamma, IFN-γ或IFN-g）濃度值與服用結核病藥物後痰液抹片從陽性轉為陰性之間的改變情形。

研究材料與方法：本研究以篩檢（Screening）的方式探討精確度指標，並利用縱貫性研究（Longitudinal Study）探討結核病患藥物治療期間，痰液抹片檢查陽轉陰前後IFN-γ濃度之變化。研究對象為某署立胸腔病院內就診或住院並完成三次AFB檢驗之高度疑似結核菌感染患者。統計方法包括使用Student t-test及卡方檢定（Chi-Square test）來分別分析連續性變項及類別變項；並使用無母數Wilcoxon Sign Rank Test之配對樣本檢定分析受試者在服用結核病藥物後其IFN-γ濃度之間的變化。

研究結果：本研究結果顯示，以痰液培養結果為判讀標準下，QuantiFERON®-TB Gold In-Tube test（QFT-GIT）之敏感度為73.08 %、特異度為51.72 %；AFB之敏感度為42.86 %、特異度則為90.00 %。另外在QFT-GIT檢驗界定值改變之下，敏感度則會從73.08 %攀升至84.62 %，但在特異度方面則會從51.72 %下降至27.59 %。此外在痰液抹片從陽性轉為陰性之際，其IFN-γ濃度反應有統計上之顯著下降（P = 0.0480）。

結論與建議：QFT-GIT檢驗在未來或許可以作為結核病高危險群之診斷工具之一，提供醫護人員另一項檢測之參考；另亦有可能進一步做為結核病病患在服用藥物之後之評估工具。最後，礙於有限之研究對象，我們仍需大量之研究對象參與，期望能建立QFT-GIT檢驗方法在台灣地區之精確度，為台灣地區結核減半十年計劃略盡棉薄之力。

Background:
Currently, screening methods of high risk of tuberculosis include tuberculin skin test (TST), sputum acid-fast staining (AFB), and interferon-gamma release assays (IGRAs). However, TST may arise false-positive result by confounded in Bacille Calmette-Guérin (BCG) vaccine. Therefore, TST is unsuitable to use on implemented BCG vaccination country. Concern AFB assay is non-specificity, IGRAs used specific antigens not affected by BCG vaccine.

Objective:
The aim of this study was to evaluate the accuracy of IGRAs as indicators in tuberculosis diagnosis, and investigate the concentration of interferon-gamma (IFN-γ) after treatment.

Materials and Method:
In this study, we used screening method to investigate accuracy indicators, conducted a longitudinal study of examination during tuberculosis treatment which sputum smear positive change to negative. The subjects completed three times AFB assay were enrolled in the study. Continuous variables were using Student t-test category variables using Chi-Square test, respectively; Wilcoxon Sign Rank method was used to test difference of IFN-γ between before and after treatment when AFB test turned into negative.

Result:
Using sputum culture result as gold standard, the sensitivity of QFT-GIT assay was 73.08%, while specificity was 51.72%; the sensitivity of AFB assay was 42.86%, specificity was 90.00%. Besides, decreasing the cut-off value of QFT-GIT assay, the sensitivity increased from 73.08% to 84.62%, while the specificity from 51.72% to 27.59%, respectively. In addition, the concentration of IFN-γ decreased significantly (p=0.0480) when sputum smear result from positive change to negative.

Conclusion:
QFT-GIT assay is an effective diagnosed tool for high risk of tuberculosis. This assay is also a good assessment tool in the future.

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