C-reactive protein cut-offs used for acute respiratory infections in Danish general practice

Abstract

Background: General practitioners (GPs) can use C-reactive protein (CRP) point-of-care test to assist when deciding whether to prescribe antibiotics for patients with acute respiratory tract infections (RTIs). Aim: To estimate which CRP cut-off levels Danish GPs use to guide antibiotic prescribing for patients presenting with different signs and symptoms of RTIs. Design and setting: Cross-sectional study. General practice in Denmark. Methods: During winter 2017 and 2018, 143 GPs and their staff registered consecutive patients with symptoms of an RTI according to the Audit Project Odense method. CRP cut-offs were estimated as the lowest level at which half of the patients were prescribed an antibiotic. Results: In total, 7,813 patients were diagnosed with an RTI of whom 4,617 (59%) had a CRP test performed. At least 25% of the patients were prescribed an antibiotic when the CRP level was above 20 mg/L, at least 50% when CRP was above 40 mg/L, and at least 75% when CRP was above 50 mg/L. Lower thresholds were identified for patients aged 65 years and those presenting with a fever, poor general appearance, dyspnoea, abnormal lung auscultation or ear/facial pain - and if the duration of symptoms was either short (≤1 day) or long (>14 days). Conclusion: More than half of patients presenting to Danish general practice with symptoms of an RTI have a CRP test performed. At CRP-levels above 40 mg/L the majority of patients have an antibiotic prescribed.