Evaluation of positive MGIT cultures with MeDiPro M. tuberculosis Ag Rapid Test for rapid identification of Mycobacterium tuberculosis Jenn-fuh Leu, Pen-Tsai Weng, I-Shan Wu, Yi-Tien Chen, Yun-Wen Sun Rui-Fu-Shi Medical Laboratory, Taichung40715, Taiwan 評估使用台塑之結核分枝桿菌快速菌種鑑定試劑快速鑑定MGIT陽性培養之結核分枝桿菌  呂振富、翁本才、吳宜珊、陳儀恬、孫韻雯 芮弗士醫事檢驗所,台中市 Background: Rapid differentiating Mycobacterium tuberculosis (MTB).from Non-tuberculous Mycobacterium (NTM) is not only important for early clinical treatment of TB but also for prevention of TB spreading. Species identification of mycobacterium requires the use of time-consuming conventional biochemical methods, or more rapid molecular techniques that are expensive and require special instrument. We evaluated the usefulness of the MeDiPro M. tuberculosis Ag Rapid Test (MeDiPro MTB)(Formosa Biomedical Technology Corp., Taiwan), a new immunochromatography method for detecting MTB specific ESAT-6 and CFP-10 antigens from culture fluid or colony re-suspension. Method: A total 522 acid fast positive smears of BACTEC MGIT (Becton Dickinson Diagnostic Systems, Sparks, MD) cultures were collected on October 2007. Each of smears was examined the microscopic morphology, including cord, pseudo-cord, needle, dot, short, ladder. All acid-fast bacilli positive MGIT cultures were incubated two more days at 37℃ incubator for bacterial enrichment¸ and than tested by MeDiPro MTB. All mycobacterium isolates were identified to species by conventional biochemical techniques. The sensitivity and the specificity of MeDiPro MTB for differentiating MTB from NTM were calculated by using conventional biochemical techniques as standard. The BDProbeTec ET system using the CTB probe (ProTec-CTB) (Becton Dichson and Co. Cockeyville, MD, USA) was applied as the third confirmation technique if the results of MeDiPro MTB and conventional biochemical techniques were discrepant. Result: Of 522 MGIT-positive cultures, 250 were identified as MTB and one mixed with MTB and M. avian complex (MAC) by conventional method. The remaining 271 cultures were NTM, including 112 MAC, 21 M. kansasii, 39 M. abscessus, 18 M. fortuitum group, 7 M. gordonae, 6 M. scrofulaceum, 2 M. mucogenicum, 3 M. marinum, 58 unidentified NTM, 3 mixed with two NTM species, 2 mixed with MAC and unidentified NTM. Of 251 MTB isolates, 250 were positive by MeDiPro MTB , including the MTB and MAC mixed culture. Of 271 NTM cultures, 8 was also positive by MeDiPro MTB. The overall sensitivity and specificity of the cording formation was calculated to be 99.6% and 97.0%. Conclusion: The results of this study manifested that the MeDiPro MTB was high sensitivity. But the specificity was affected as a result of some clinical important NTM being detected as positive also. We suggest that the cord formation of acid fast positive smears of MGIT can be employed as a screen examination for MTB, it could exclude false positive of NTM in advance. The specificity of MeDiPro MTB combing with the cord formation will arise from 97.0% to 99.6% (270/271), but the sensitivity will falloff from 99.6% to 98.8% (248/251).