Comparison of acute-phase reactants in pediatric patients with fever.

We compared WBC count greater than or equal to 15,000/cu mm (high WBC count). Wintrobe ESR greater than or equal to 30 mm/hr (high ESR), temperature greater than or equal to 40 degrees C, and positive slide tests for C-reactive protein (CRP) at a serum dilution of 1:50 in febrile, ambulatory children. The CRP test was performed with and without heat inactivation of serum. An excellent correlation was found between noninactivated and inactivated CRP test results. Since the noninactivated CRP test can be done quickly, its results would be readily available in an outpatient setting. High ESR demonstrated the best balance of specificity and sensitivity for bacteremia, pneumonia, and other possible or proved bacterial illnesses. A positive CRP test was highly specific for these diagnoses but less sensitive than an ERS greater than or equal to 30 mm/hr. Three combinations of acute-phase reactants, high WBC count and/or high ESR, high ESR and/or positive CRP test, and high WBC count and/or high ESR and/or positive CRP test performed as well as high ESR alone. Each was less specific but more sensitive than high ESR for possible or proved bacterial illnesses. The evaluation of an ambulatory, febrile child with acute-phase reactants should include at least determination of ESR.