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

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.