Use of time from fever onset improves the diagnostic accuracy of C-reactive protein in identifying bacterial infections.
OBJECTIVE
To determine whether the input of time from fever onset will change the accuracy of C-reactive protein (CRP) in diagnosing bacterial infections in febrile children.


METHODS
We performed a prospective observational study on febrile children presenting to the emergency department. The diagnostic performance of CRP at different time points from fever onset was compared using a receiver operating characteristic (ROC) curve.


RESULTS
Among 373 patients included, 103 (28%) had bacterial infection. The optimal cut-off for CRP suggesting bacterial infection changed with time from fever onset: 6 mg/dL for >12-24 h of fever; 10.7 and 12.6 mg/dL at >24-48 and >48 h of fever, respectively. The input of time from fever onset improved the area under the ROC curve from 0.83 (95% CI 0.78 to 0.88) for CRP overall to 0.87 (95% CI 0.77 to 0.96) and 0.90 (95% CI 0.84 to 0.97) at >24-48 and >48 h of fever, respectively. Duration of fever mostly affected the ability of CRP to correctly rule out bacterial infections. CRP level of 2 mg/dL obtained at ≤24 h of fever corresponds with a post-test probability for bacterial infection of 10%, whereas the same value obtained >24 h of fever reduces the risk to 2%.


CONCLUSIONS
Clinicians should apply different CRP cut-off values depending on whether they are trying to rule in or rule out bacterial infection, but also depending on fever duration at the time of CRP testing.
Paediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel.
Idan
I
Segal
Paediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel Faculty of Medicine, Hebrew University, Jerusalem, Israel.
Matityahu
M
Ehrlichman
Paediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel.
Joseph
J
Urbach
Paediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel Faculty of Medicine, Hebrew University, Jerusalem, Israel.
Maskit
M
Bar-Meir
D000293:Adolescent; D001424:Bacterial Infections / Q000097:blood / Q000175:diagnosis*; D002097:C-Reactive Protein / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D004636:Emergency Service, Hospital; D005260:Female; D005334:Fever / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D007223:Infant; D008297:Male; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013997:Time Factors
D002097:C-Reactive Protein