LABORATORY TESTS IN EVALUATION OF ACUTE FEBRILE ILLNESS IN PEDIATRIC EMERGENCY ROOM PATIENTS

The rising costs of health care and the movement for health care refor m have focused attention on methods of cost containment. Of routine la boratory and radiologic procedures, complete blood cell count (CBC) an d determination of serum electrolyte values rank as high as 2nd and 9t h in overall cost. We retrospectively studied use of the clinical labo ratory to aid diagnosis of an acute infectious event in a pediatric em ergency department population. For 5 months, we reviewed medical recor ds of pediatric patients younger than 15 years brought to the emergenc y department because of a febrile episode. Of 155 cases reviewed, elec trolyte concentrations were determined in 108 patients and CBC in 155. In all patients, either culture or rapid test for streptococcal organ isms was performed. In addition, 838 pediatric patients with similar s ymptoms but who did not undergo laboratory testing were monitored for 100 days. Measures of effectiveness including sensitivity, specificity , positive and negative predictive values, and likelihood ratio were u sed to correlate specific laboratory findings with antibiotic therapy, serious bacterial disease, and culture positivity. Electrolyte abnorm alities were found largely to be dismissed clinically, with the major clinical response consisting of parental education about hydration. Th e CBC profile was evaluated, with white blood cell count (WBC) indicat or limits of >10,000, >10,000 but <15,000, and >15,000/mm(3), and diff erentiated into absolute neutrophil count, neutrophil percent, and ban d cell percent. Temperature was evaluated as an independent variable. Insofar as serious bacterial disease and culture positivity sensitivit y was uniformly low (70%), and specificity was only marginably accepta ble for WBC >15,000 (77%). Both positive predictive values and likelih ood ratio were low with respect to predicting either serious bacterial disease or culture positivity, emphasizing the limited usefulness of these clinical laboratory measurements. The best hematologic predictor s of serious bacterial disease or culture positivity were obtained wit h automated hematologic analyzers and exceeded manual differential mea surement of neutrophil percent and band cell percent. In addition, we correlated the administration of antibiotics with the various hematolo gic parameters and discovered that WBC >15,000, regardless of cause, a lmost uniformly resulted in treatment (positive predictive value, 93.5 %; likelihood ratio, 5.60). These findings support the use of automate d hematology analyzer-derived measurements and question the use of man ual differential counts, unless specific issues are to be addressed. F urthermore, the findings seem to support more reliance on clinical imp ression and less on laboratory values.