Accuracy of Biomarkers for the Diagnosis of Adult Community‐acquired Pneumonia: A Meta‐analysis

Abstract

Background Biomarkers such as C‐reactive protein (CRP) and procalcitonin may help distinguish community‐acquired pneumonia (CAP) from other causes of lower respiratory tract infection. Methods 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. Results 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. Conclusions The best evidence supports CRP as the preferred biomarker for diagnosis of outpatient CAP given its accuracy, low cost, and point‐of‐care availability.

Clinical characteristics and predictors of pneumonia in patients presenting fever or respiratory symptoms with normal or low leukocyte counts: a retrospective study

“…[23] However, some researchers found that the CRP level did not improve the prediction of pneumonia; instead, it can help clinicians make a decision regarding the use of antibiotics. [24,25] In contrast to previous studies [11,20], we found that a hsCRP level of 1.64 mg/L had a negative likelihood ratio of 0.07 in the ROC analysis, which means it was a strong predictor of the absence of pneumonia in patients with normal or low leukocyte counts. Further investigations showed that three patients had a hsCRP level less than 1.64 mg/L in the pneumonia group, two of whom were diagnosed with COVID-19 according to the Chinese management guidelines (version 7.0) [15].…”

“…It was identi ed as a predictor of pneumonia in several studies. [11,[20][21][22] A CRP level ≤ 10 mg/L was useful for ruling out CAP in most patients. [11]Steurer et al found there was no pneumonia diagnosed when the CRP levels were < 10 mg/L or if the CRP levels were between 11 and 50 mg/L and the patient did not complain of dyspnea and fever associated with cough.…”

“…[11,[20][21][22] A CRP level ≤ 10 mg/L was useful for ruling out CAP in most patients. [11]Steurer et al found there was no pneumonia diagnosed when the CRP levels were < 10 mg/L or if the CRP levels were between 11 and 50 mg/L and the patient did not complain of dyspnea and fever associated with cough. [23] However, some researchers found that the CRP level did not improve the prediction of pneumonia; instead, it can help clinicians make a decision regarding the use of antibiotics.…”

“…[10] A recent meta-analysis evaluating the accuracy of biomarkers such as CRP and procalcitonin in patients with acute cough or suspected CAP showed that CRP was the preferred biomarker for the diagnosis of outpatient CAP with a positive likelihood ratio (+ LR) and a negative likelihood ratio (-LR) of 2.08 and 0.32, respectively, for a cutoff value of 20 mg/L; 3.64 and 0.36, respectively, for a cutoff value of 50 mg/L; and 5.89 and 0.47, respectively, for a cutoff value of 100 mg/L. [11] However, the best indicator of pneumonia in patients with normal or low leukocyte counts is still unknown.…”

Diagnosing pneumonia in primary care : Aspects of the value of clinical and laboratory findings and the use of chest X-ray

“…However, CRP testing has also been shown to decrease antibiotic prescription rates and is sometimes used as a decision aid to determine whether or not to request a CXR [105][106][107][108][109][110]. Further, CRP has been suggested as the preferred biomarker, alone and as part of a CDR for diagnosis of CAP in primary care [70,111,112].…”