University of Georgia, Athens, GA.
Acad Emerg Med. 2020 Mar;27(3):195-206. doi: 10.1111/acem.13889. Epub 2020 Feb 26.
Biomarkers such as C-reactive protein (CRP) and procalcitonin may help distinguish community-acquired pneumonia (CAP) from other causes of lower respiratory tract infection.
We performed a systematic review of the literature to identify prospective studies evaluating the accuracy of a biomarker in patients with acute cough or suspected CAP. We performed parallel abstraction of data regarding study inclusion, characteristics, quality, and test accuracy. Study quality was evaluated using QUADAS-2. Bivariate meta-analysis was performed using the mada package in R, and summary receiver operating characteristic (ROC) curves were created.
Fourteen studies met our inclusion and exclusion criteria; three were at low risk of bias and four at moderate risk of bias, largely due to failure to prespecify diagnostic thresholds. Considering all studies regardless of the cutoff used, CRP was most accurate (area under the ROC curve = 0.802), followed by leukocytosis (0.777) and procalcitonin (0.771). Lipopolysaccharide-binding protein and fibrinogen are promising, but were only studied in a single report. For CRP and procalcitonin, the positive and negative likelihood ratios (LR+ and LR-, respectively) varied inversely based on the cutoff. For CRP, LR+ and LR- were 2.08 and 0.32 for a cutoff of 20 mg/L, 3.64 and 0.36 for a cutoff of 50 mg/L, and 5.89 and 0.47 for a cutoff of 100 mg/L. For procalcitonin, LR+ and LR- were 2.50 and 0.39 for a cutoff of 0.10 µg/L, 5.43 and 0.62 for a cutoff of 0.25 µg/L, and 8.25 and 0.76 for a cutoff of 0.50 µg/L. The combination of CRP >49.5 mg/L and procalcitonin >0.1 µg/L had LR+ of 2.24 and LR- of 0.44.
The best evidence supports CRP as the preferred biomarker for diagnosis of outpatient CAP given its accuracy, low cost, and point-of-care availability.
C 反应蛋白（CRP）和降钙素原等生物标志物有助于将社区获得性肺炎（CAP）与下呼吸道感染的其他病因区分开来。
我们对文献进行了系统回顾，以确定评估生物标志物在急性咳嗽或疑似 CAP 患者中的准确性的前瞻性研究。我们平行提取了关于研究纳入、特征、质量和检测准确性的数据。使用 R 中的 mada 包进行双变量 meta 分析，并创建汇总受试者工作特征（ROC）曲线。
有 14 项研究符合我们的纳入和排除标准；其中 3 项研究的偏倚风险较低，4 项研究的偏倚风险为中度，主要是因为没有预先指定诊断阈值。考虑到所有研究，而不管使用的截止值如何，CRP 的准确性最高（ROC 曲线下面积为 0.802），其次是白细胞增多症（0.777）和降钙素原（0.771）。脂多糖结合蛋白和纤维蛋白原很有前途，但仅在一份报告中进行了研究。对于 CRP 和降钙素原，阳性和阴性似然比（LR+和 LR-）分别根据截止值呈反比变化。对于 CRP，在 20mg/L 的截止值下，LR+和 LR-分别为 2.08 和 0.32，在 50mg/L 的截止值下，LR+和 LR-分别为 3.64 和 0.36，在 100mg/L 的截止值下，LR+和 LR-分别为 5.89 和 0.47。对于降钙素原，在 0.10μg/L 的截止值下，LR+和 LR-分别为 2.50 和 0.39，在 0.25μg/L 的截止值下，LR+和 LR-分别为 5.43 和 0.62，在 0.50μg/L 的截止值下，LR+和 LR-分别为 8.25 和 0.76。CRP>49.5mg/L 和降钙素原>0.1μg/L 的组合的 LR+为 2.24，LR-为 0.44。
鉴于 CRP 的准确性、低成本和即时可用性，最佳证据支持 CRP 作为诊断门诊 CAP 的首选生物标志物。
