Medical Care Line (Infectious Disease Section), Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX, USA.
J Infect. 2013 Jul;67(1):11-8. doi: 10.1016/j.jinf.2013.03.003. Epub 2013 Mar 19.
Determining the cause of community-acquired pneumonia (CAP) remains problematic. In this observational study, we systematically applied currently approved diagnostic techniques in patients hospitalized for CAP in order to determine the proportion in which an etiological agent could be identified.
All patients admitted with findings consistent with CAP were included. Sputum and blood cultures, urine tests for pneumococcal and Legionella antigens, nasopharyngeal swab for viral PCR, and serum procalcitonin were obtained in nearly every case. Admission-related electronic medical records were reviewed in entirety.
By final clinical diagnosis, 44 patients (17.0%) were uninfected. A causative bacterium was identified in only 60 (23.2%) cases. PCR identified a respiratory virus in 42 (16.2%), 12 with documented bacterial coinfection. In 119 (45.9%), no cause for CAP was found; 69 (26.6%) of these had a syndrome indistinguishable from bacterial pneumonia. Procalcitonin was elevated in patients with bacterial infection and low in uninfected patients or those with viral infection, but with substantial overlap.
Only 23.2% of 259 patients admitted with a CAP syndrome had documented bacterial infection; another 26.6% had no identified bacterial etiology, but findings closely resembled those of bacterial infection. Nevertheless, all 259 received antibacterial therapy. Careful attention to the clinical picture may identify uninfected patients or those with viral infection, perhaps with reassurance by a non-elevated procalcitonin. Determining an etiologic diagnosis remains elusive. Better discriminators of bacterial infection are sorely needed.
确定社区获得性肺炎（CAP）的病因仍然存在问题。在这项观察性研究中，我们系统地应用了目前批准的诊断技术，对因 CAP 住院的患者进行检测，以确定能够确定病因的比例。
所有符合 CAP 发现标准的患者均被纳入研究。几乎每例患者均获得痰和血培养、尿肺炎球菌和军团菌抗原检测、鼻咽拭子病毒 PCR 检测和血清降钙素原检测。还对入院相关的电子病历进行了全面回顾。
根据最终临床诊断，44 例（17.0%）患者无感染。仅在 60 例（23.2%）患者中确定了病原体。PCR 鉴定出 42 例（16.2%）呼吸道病毒，其中 12 例有明确的细菌合并感染。119 例（45.9%）未发现 CAP 病因；其中 69 例（26.6%）患者的综合征与细菌性肺炎无法区分。细菌性感染患者的降钙素原升高，未感染患者或病毒感染患者的降钙素原降低，但存在大量重叠。
259 例 CAP 综合征患者中，仅有 23.2%的患者有明确的细菌感染；另有 26.6%的患者未确定细菌病因，但表现与细菌性感染非常相似。然而，所有 259 例患者均接受了抗菌治疗。仔细观察临床情况可能会发现未感染的患者或病毒感染患者，也许降钙素原不升高可以带来一定程度的安心。确定病因诊断仍然困难。目前迫切需要更好的细菌感染鉴别指标。
