Considering CRP Concentration Improves Diagnosis of Pneumonia

Low C-reactive protein levels helped rule out pneumonia.

Acute bronchitis is managed expectantly, and pneumonia is managed with antibiotics. However, accurately distinguishing these conditions, based on history and physical examination alone, is difficult. Although chest x-ray can distinguish acute bronchitis from pneumonia, it is expensive, exposes patients to radiation (often unnecessarily), and is unavailable in some settings. In this European study, investigators determined whether measuring blood C-reactive protein (CRP) and procalcitonin concentrations, in addition to history and physical examination, improved diagnostic accuracy.

Among 2820 adults (mean age, 50) who presented with cough to primary care practices, chest x-ray confirmed pneumonia in 140 patients (5%). The optimum combination of history and examination findings for pneumonia was absence of runny nose and presence of breathlessness, crackles and diminished breath sounds on auscultation, tachycardia, and fever. Adding CRP level as a continuous variable resulted in significantly improved ability to predict pneumonia (multivariate odds ratio, 1.2 per 10 mg/L rise in CRP concentration). Adding CRP as a dichotomized variable (>30 mg/L as high-risk for pneumonia) yielded similar results. Of 665 patients with low probability (<2.5%) for pneumonia based on history and examination findings only, 11 (2%) actually had pneumonia. Adding CRP level reclassified 891 additional patients in

CITATION(S):

van Vugt SF et al. Use of serum C reactive protein and procalcitonin concentrations in addition to symptoms and signs to predict pneumonia in patients presenting to primary care with acute cough: Diagnostic study. BMJ 2013 Apr 30; 346:f2450.