Context Recent guidelines for management of pharyngitis vary in their recommendations
concerning empirical antibiotic treatment and the need for laboratory confirmation
of group A streptococcus (GAS).
Objective To assess the impact of guideline recommendations and alternative approaches
on identification and treatment of GAS pharyngitis in children and adults.
Design, Setting, and Participants Throat cultures and rapid antigen tests were performed on 787 children
and adults aged 3 to 69 years with acute sore throat attending a family medicine
clinic in Calgary, Alberta, from September 1999 to August 2002. Recommendations
from 2 guidelines (those of the Infectious Diseases Society of America and
of the American College of Physicians-American Society of Internal Medicine/American
Academy of Family Physicians/US Centers for Disease Control and Prevention)
were compared with rapid testing alone, a clinical prediction rule (ie, the
modified Centor score), and a criterion standard of treatment for positive
throat culture results only.
Main Outcome Measures Sensitivity and specificity of each strategy for identifying GAS pharyngitis,
total antibiotics recommended, and unnecessary antibiotic prescriptions.
Results In children, sensitivity for streptococcal infection ranged from 85.8%
(133/155; 95% confidence interval [CI], 79.3%-90.0%) for rapid testing to
100% for culturing all. In adults, sensitivity ranged from 76.7% (56/73; 95%
CI, 65.4%-85.8%) for rapid testing without culture confirmation of negative
results to 100% for culturing all. In children, specificity ranged from 90.3%
(270/299; 95% CI, 86.4%-93.4%) for use of modified Centor score and throat
culture to 100% for culturing all. In adults, specificity ranged from 43.8%
(114/260; 95% CI, 37.7%-50.1%) for empirical treatment based on a modified
Centor score of 3 or 4 to 100% for culturing all. Total antibiotic prescriptions
were lowest with rapid testing (24.7% [194/787]; 95% CI, 21.7%-27.8%) and
highest with empirical treatment of high-risk adults (45.7% [360/787]; 95%
CI, 42.2%-49.3%), due to a high rate of unnecessary prescriptions in adults
(43.8% [146/333]; 95% CI, 38.4%-49.4%).
Conclusions Guideline recommendations for the selective use of throat cultures but
antibiotic treatment based only on positive rapid test or throat culture results
can reduce unnecessary use of antibiotics for treatment of pharyngitis. However,
empirical treatment of adults having a Centor score of 3 or 4 is associated
with a high rate of unnecessary antibiotic use. In children, strategies incorporating
throat culture or throat culture confirmation of negative rapid antigen test
results are highly sensitive and specific. Throat culture of all adults or
those selected on the basis of a clinical prediction rule had the highest
sensitivity and specificity.