BACKGROUND: Rapid antigen detection testing (RADT) is often performed for 
diagnosis of group A beta-hemolytic streptococcal (GABHS) pharyngitis among 
children. Among adults, the sensitivity of this test varies on the basis of 
disease severity (spectrum bias). A similar phenomenon may occur when this test 
is used in a pediatric population, which may affect the need for culture 
confirmation of all negative RADT results.
OBJECTIVES: To assess the performance of a clinical scoring system and to 
determine whether RADT spectrum bias is present among children who are evaluated 
for GABHS pharyngitis.
METHODS: Laboratory and clinical records for a consecutive series of pediatric 
patients who underwent RADT at the Marshfield Clinic between January 2002 and 
March 2002 were reviewed retrospectively. Patients were stratified according to 
the number of clinical features present by using modified Centor criteria, ie, 
history of fever, absence of cough, presence of pharyngeal exudates, and 
cervical lymphadenopathy. The sensitivity of the RADT was defined as the number 
of patients with positive RADT results divided by the number of patients with 
either positive RADT results or negative RADT results but positive throat 
culture results.
RESULTS: RADT results were positive for 117 of 561 children (21%), and culture 
results were positive for 35 of 444 children (8%) with negative RADT results. 
The overall prevalence of GABHS pharyngitis was 27% (95% confidence interval: 
23-31%). The prevalence of GABHS pharyngitis was 18% among patients with 0 
Centor criteria, 16% among those with 1 criterion, 32% among those with 2 
criteria, and 50% among those with 3 or 4 criteria. Spectrum bias was present, 
inasmuch as RADT sensitivity increased with Centor scores, ie, 47% sensitivity 
among children with 0 Centor criteria, 65% among those with 1 criterion, 82% 
among those with 2 criteria, and 90% among those with 3 or 4 criteria.
CONCLUSIONS: The sensitivity of RADT for GABHS pharyngitis is not a fixed value 
but varies with the severity of disease. However, even among pediatric patients 
with > or =3 Centor criteria for GABHS pharyngitis, the sensitivity of RADT is 
still too low to support the use of RADT without culture confirmation of 
negative results.