結核分枝桿菌聚合酶鏈鎖反應檢測、抗酸抹片、胸部X 光檢查與分枝桿菌培養結果的比較分析

Comparative Analysis of Mycobacterium Tuberculosis-polymerase Chain Reaction Testing, Acid-fast Smears, and Chest X Ray Examination Against Mycobacterial Culture Results

肺結核的早期診斷對於適當的抗結核藥物治療和進行必要的感染管制措施非常重要。在台灣，大多數醫院仍依賴抗酸桿菌鏡檢、胸部X光檢查、以及結核菌培養來診斷肺結核。本回顧性研究旨在評估結核分枝桿菌聚合酶鏈鎖反應(Mycobacterium tuberculosis-polymerase chain reaction,TB-PCR)對於診斷肺結核的貢獻。在南台灣一個600床的地區醫院，所有在2012年6月和2014年12月間痰液培養得到結核分枝桿菌複合體(Mycobacterium tuberculosis complex, MTBC)和非結核分枝桿菌(nontuberculous mycobacteria, NTM)的陽性結果均進行分析。去除來自同一個病人的重複結果後，共有249陽性結果（152個MTBC與97個NTM）被納入分析。經過病歷審閱，有30例(30.9％)被確認為NTM肺部感染。抗酸桿菌鏡檢對肺結核(29.6％)和NTM肺部感染(30.0％)個案的檢出率類似。有19.1％的肺結核個案和36.7％的NTM肺部感染個案，在胸部X光檢查的結果為“疑似肺結核”(P < 0.05)。在研究期間，共有40痰液檢體進行TB-PCR檢測。其中11例為陽性，而且，它們的結核菌培養結果也都有MTBC的陽性生長。在剩餘的29例TB-PCR陰性個案中，有5例因為結核菌培養羊幸而被診斷為結核感染個案。因此，TB-PCR檢測的特異性和陽性預測值均可達到100％。雖然整體靈敏度(68.8％)較低，但若只分析抗酸桿菌鏡檢陽性個案，或是胸部X光檢查為疑似肺結核的個案，則TB-PCR的靈敏度會增加為100％。TB-PCR顯然是一種有效的工具，可以對於肺部分枝桿菌感染作正確的鑑別診斷。關於NTM感染的全球性增長仍然持續被報告中，將TB-PCR檢測納入常規的肺結核感染實驗室診斷方法中，顯然有其必要性。

Early diagnosis of tuberculosis (TB) is essential for appropriate anti-TB treatment and necessary for infection control measures. Diagnosis of pulmonary TB relies on microscopic examination of acid-fast bacilli (AFB), chest X-ray (CXR) examination, and mycobacterial cultures in most hospitals in Taiwan. The present study was conducted retrospectively to evaluate the contribution of a Mycobacterium tuberculosis-polymerase chain reaction (TB-PCR) method in the diagnosis of pulmonary TB. At a 600-bed regional hospital in southern Taiwan, records of all sputum cultures with positive findings of M. tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM) between June 2012 and December 2014 were analyzed. After removal of duplicate results from the same patients, 249 positive results (MTBC, n = 152; NTM, n = 97) were identified. Review of medical records revealed 30 (30.9%) cases of pulmonary NTM infection. The detection rates of TB (29.6%) and pulmonary NTM (30.0%) cases by AFB smears were similar. By CXR examination, the report of “suspected pulmonary TB” was noted in 19.1% of TB and 36.7% of pulmonary NTM cases (P < 0.05). During the study period, 40 sputum specimens were examined by TB-PCR. Positive results were found in 11 cases, all of which were also culture-positive for MTBC organisms. Five of the 29 TB-PCR-negative cases were diagnosed as TB infection by mycobacterial culture. Hence, the specificity and positive predictive value of TB-PCR were both high at 100%. Although the overall sensitivity (68.8%) was lower, an increase to 100% was observed in AFB smear positive cases or suspected TB cases by CXR examination. TB-PCR is apparently an efficient tool for the correct differential diagnosis of pulmonary mycobacterial infections. As global increase of NTM infections is continuously reported, the incorporation of TB-PCR examination as a part of routine laboratory diagnosis methods for TB infection appears necessary.