Bedside procalcitonin and C-reactive protein tests in children with fever without localizing signs of infection seen in a referral center

Objective. To assess the value of bedside tests for predicting the occurrence of severe bacterial infections (SBIs) in children with fever without source. Methods. We conducted a prospective study of 99 children, aged 7 days to 36 months, who were seen for fever >38degreesC and no localizing sign of infection at the emergency department of the University Children's Hospital of Geneva. Blood procalcitonin (PCT), C-reactive protein (CRP), and interleukin-6 (IL-6) values were determined using rapid tests and were compared with the total white blood cell (WBC) count with differential and clinical score. Specificity, sensitivity, predictive values, and multilevel likelihood ratios (LRs) with posttest probabilities of disease were calculated. Results. Twenty-nine (29%) children received a diagnosis of having an SBI. PCT had the best sensitivity (93%) and negative predictive value (96%). Band count had the best specificity (93%), but its positive predictive value was only 38%. Multilevel LRs revealed that a PCT concentration <0.5 ng/mL (LR:0.093) almost ruled out SBI (posttest probability of disease: 3.7%) in 54 (54%) subjects, whereas a value >2 ng/mL (LR:5.2) increased the probability of SBI to 68% in 19 (19%) children. For CRP, values <40 mg/L (LR:0.263) and >100 mg/L (LR:14.483) generated posttest probabilities for SBI of 9.7% (61 subjects) and 86.5% (14 subjects), respectively. For WBC count, the posttest probabilities of SBI were modestly changed from the pretest prevalence. Conclusions. PCT and CRP performed better than IL-6, WBC, and/or band count in predicting the occurrence of SBI. PCT and CRP bedside tests may be useful tools for emergency and private practice doctors and should be considered in the initial work-up of children with fever without source.