C-reactive protein level as diagnostic marker in young febrile children presenting in a general practice out-of-hours service

Background: it is unclear how well a c-reactive protein (crp) value predicts a serious infection (si) in young febrile children in general practice. methods: this prospective cohort study with 1-week follow-up included children,aged 3 months to 6 years,presenting with fever to a general practitioner out-of-hours service. we evaluate whether crp level has predictive value for diagnosing a child at risk for an si either at presentation or during followup. the index test was crp <20 mg/l (rule out an si) and >80 mg/l (rule in an si). the reference standard was referral to a pediatric emergency department or diagnosis of an si. the main outcome measure was crp value. results: crp level was available for 440 children. to rule out an si,crp <20 mg/l did not change the probability of having no si (87.5%). crp >80 mg/l increased the probability of having an si from 11.4% (pretest probability) to 21.2% (posttest probability). in children without a diagnosis of si at presentation,crp could not predict an si during follow-up (crp >80 mg/l: positive likelihood ratio,2.1,95% confidence interval,1.3-3.5; crp <20 mg/l: negative likelihood ratio,0.9,95% confidence interval,0.7-1.2). conclusions: in general practice crp has little clinically relevant value in discriminating febrile children in need of medical care from those who are not.