Gw. Procop et al., LABORATORY TESTS IN EVALUATION OF ACUTE FEBRILE ILLNESS IN PEDIATRIC EMERGENCY ROOM PATIENTS, American journal of clinical pathology, 107(1), 1997, pp. 114-121
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.