Bjarnason A, Lindh M, Westin J, Andersson L-M, Baldursson O, Kristinsson K G, Gottfredsson M
Faculty of Medicine, University of Iceland, Reykjavik, Vatnsmyrarvegi 16, 101, Reykjavik, Iceland.
Departments of Medicine, Microbiology and Virology, Landspitali University Hospital, 101, Reykjavik, Iceland.
Eur J Clin Microbiol Infect Dis. 2017 Mar;36(3):529-536. doi: 10.1007/s10096-016-2829-z. Epub 2016 Nov 7.
A lack of sensitive tests and difficulties obtaining representative samples contribute to the challenge in identifying etiology in pneumonia. Upper respiratory tract swabs can be easily collected and analyzed with real-time PCR (rtPCR). Common pathogens such as S. pneumoniae and H. influenzae can both colonize and infect the respiratory tract, complicating the interpretation of positive results. Oropharyngeal swabs were collected (n = 239) prospectively from adults admitted to hospital with pneumonia. Analysis with rtPCR targeting S. pneumoniae and H. influenzae was performed and results compared with sputum cultures, blood cultures, and urine antigen testing for S. pneumoniae. Different Ct cutoff values were applied to positive tests to discern colonization from infection. Comparing rtPCR with conventional testing for S. pneumoniae in patients with all tests available (n = 57) resulted in: sensitivity 87 %, specificity 79 %, PPV 59 % and NPV 94 %, and for H. influenzae (n = 67): sensitivity 75 %, specificity 80 %, PPV 45 % and NPV 94 %. When patients with prior antimicrobial exposure were excluded sensitivity improved: 92 % for S. pneumoniae and 80 % for H. influenzae. Receiver operating characteristic curve analysis demonstrated for S. pneumoniae: AUC = 0.65 (95 % CI 0.51-0.80) and for H. influenzae: AUC = 0.86 (95 % CI 0.72-1.00). Analysis of oropharyngeal swabs using rtPCR proved both reasonably sensitive and specific for diagnosing pneumonia caused by S. pneumoniae and H. influenzae. This method may be a useful diagnostic adjunct to other methods and of special value in patients unable to provide representative lower airway samples.
缺乏敏感的检测方法以及获取具有代表性样本的困难，给肺炎病因的确定带来了挑战。上呼吸道拭子易于采集，并可通过实时聚合酶链反应（rtPCR）进行分析。肺炎链球菌和流感嗜血杆菌等常见病原体既能定植于呼吸道，也能引起呼吸道感染，这使得阳性结果的解读变得复杂。前瞻性地收集了239例因肺炎入院的成年人的口咽拭子。采用针对肺炎链球菌和流感嗜血杆菌的rtPCR进行分析，并将结果与痰培养、血培养以及肺炎链球菌尿抗原检测结果进行比较。对阳性检测结果应用不同的Ct临界值来区分定植与感染。在所有检测均可用的患者中（n = 57），将rtPCR与肺炎链球菌的传统检测方法进行比较，结果如下：敏感性87%，特异性79%，阳性预测值59%，阴性预测值94%；对于流感嗜血杆菌（n = 67）：敏感性75%，特异性80%，阳性预测值45%，阴性预测值94%。排除先前有抗菌药物暴露史的患者后，敏感性有所提高：肺炎链球菌为92%，流感嗜血杆菌为80%。受试者工作特征曲线分析显示，肺炎链球菌的曲线下面积（AUC）= 0.65（95%置信区间0.51 - 0.80），流感嗜血杆菌的AUC = 0.86（95%置信区间0.72 - 1.00）。使用rtPCR对口咽拭子进行分析，对于诊断由肺炎链球菌和流感嗜血杆菌引起的肺炎具有合理的敏感性和特异性。该方法可能是其他方法有用的诊断辅助手段，对于无法提供具有代表性的下呼吸道样本的患者具有特殊价值。
