Background: C-reactive protein (CRP) and procalcitonin (PCT) are useful diagnostic tools to estimate the risk of serious bacterial infection (SBI) in febrile children at the emergency department (ED). The Lab-score combines these 2 biomarkers with urinalysis in an easy to use validated model. Kinetics of inflammatory markers suggests a differentiating role of duration of disease.
Aim: : Appraisal of the diagnostic role of CRP and PCT in febrile children at risk of SBI, determining the differentiating value of duration of fever, and validating and updating the Lab-score.
Methods: In this prospective observational study previously healthy children with fever, 1 month to 16 years of age, attending the EDs of a university hospital and a teaching hospital (Rotterdam, the Netherlands) between 2009 and 2012 were included. Standardized information on clinical signs and symptoms, CRP, PCT and urinalysis were collected prospectively. Logistic multivariable regression analysis was used to assess diagnostic performance. The original Lab-score included CRP, PCT and urinalysis and the total score ranged 0-9 points.
Results: One thousand eighty-four children were included, median age was 1.6 years (interquartile range: 0.8-3.5), 170 children (16%) had SBI. CRP [receiver operating characteristic (ROC)-area 0.77 (95% confidence interval [CI]: 0.69-0.85)] and PCT [ROC-area 0.75 (95% CI: 0.67-0.83)] were both strong predictors of SBI. Duration of fever had no added diagnostic value to CRP and PCT. The Lab-score performed well [ROC area 0.79 (95% CI: 0.72-0.87)], but threshold values performed similar to often used cutoffs of single biomarkers. An updated Lab-score improved only moderately [ROC area 0.83 (95% CI: 0.76-0.90)]. PCT did not alter post-test probabilities for SBI substantially in patients with low (<20 mg/L) or elevated CRP (≥ 100 mg/L) levels (67% of population).
Conclusion: CRP and PCT were both strong predictors of SBI. The original and updated Lab-score performed well, but thresholds values lacked diagnostic value for ruling out SBI. Depending on clinical risk thresholds, diagnostic testing can be limited to CRP or PCT, rather than both, in many febrile children.