Hamdi Ahmed, Fida Madiha, Deml Sharon M, Abu Saleh Omar, Wengenack Nancy L
Division of Infectious Diseases, Mayo Clinic, Rochester, MN, United States.
Division of Clinical Microbiology, Mayo Clinic, Rochester, MN, United States.
J Clin Tuberc Other Mycobact Dis. 2020 Aug 17;21:100181. doi: 10.1016/j.jctube.2020.100181. eCollection 2020 Dec.
To analyze and interpret clinical microbiology data for specimens tested with the fluorochrome stain (AFB stain), mycobacterial culture and a laboratory-developed (MTB) PCR in order to understand the performance of each test and to demonstrate the utility of MTB PCR to assist with decisions regarding discontinuation of airborne isolation.
Retrospective cohort analysis of 2798 respiratory specimens from 2006 patients in the period between November 1st, 2011 and January 1st, 2018.
53.7% were males, median age was 61 years, and 43 patients were HIV positive. Results demonstrated positive mycobacterial cultures for MTB in 52 specimens (1.9%) and for nontuberculous mycobacteria (NTM) or aerobic actinomycetes (eg., spp.) in 435 specimens (16%). Using mycobacterial culture as the gold standard, AFB smear had a sensitivity of 48.1% while MTB PCR had a sensitivity of 96.0% in AFB smear positive specimens and an overall sensitivity of 57.7% with PPV of 94% and a NPV of 99%.
The combination of a positive AFB smear with a negative MTB PCR offers a rapid result to rule out active pulmonary MTB in a low prevalence setting. In this study, that combination reliably excluded active tuberculosis (NPV of 99.2%). The combination of a positive AFB smear with a negative MTB PCR indicated pulmonary NTM infection with the results available within 1 day. There was little benefit to pursuing collection and testing of more than 2 respiratory specimens in a low prevalence setting for both long term diagnostic or rapid isolation discontinuation purposes.
分析和解读用荧光染色（抗酸杆菌染色）、分枝杆菌培养及实验室自建的结核分枝杆菌（MTB）聚合酶链反应（PCR）检测的标本的临床微生物学数据，以了解每项检测的性能，并证明MTB PCR在协助决定解除空气隔离方面的实用性。
对2011年11月1日至2018年1月1日期间2006例患者的2798份呼吸道标本进行回顾性队列分析。
男性占53.7%，中位年龄为61岁，43例患者HIV阳性。结果显示，52份标本（1.9%）的MTB分枝杆菌培养呈阳性，435份标本（16%）的非结核分枝杆菌（NTM）或需氧放线菌（如诺卡菌属）培养呈阳性。以分枝杆菌培养为金标准，抗酸杆菌涂片在抗酸杆菌涂片阳性标本中的敏感性为48.1%，而MTB PCR的敏感性为96.0%，总体敏感性为57.7%，阳性预测值为94%，阴性预测值为99%。
抗酸杆菌涂片阳性而MTB PCR阴性的组合可快速得出结果，以排除低患病率环境中的活动性肺结核。在本研究中，该组合可靠地排除了活动性结核病（阴性预测值为99.2%）。抗酸杆菌涂片阳性而MTB PCR阴性的组合表明为肺部NTM感染，结果可在1天内获得。在低患病率环境中，为了长期诊断或快速解除隔离的目的，采集和检测超过2份呼吸道标本几乎没有益处。
