Group A streptococcal infection in patients presenting with a sore throat at an accident and emergency department: prospective observational study.
Objective: To determine the prevalence of group A streptococcal infection and to evaluate the predictive value of clinical findings and rapid streptococcal antigen detection testing in patients presenting with a sore throat or suspected clinically to have acute pharyngitis.
Methods: Prospective observational study. Methods: Accident and emergency department of a public hospital, Hong Kong. Methods: All patients presenting with a sore throat as the chief complaint, or suspected clinically to have acute pharyngitis, from April to September 2000. Methods: Demographic data, clinical features, microbiological throat culture results, and rapid streptococcal antigen detection (Accustrip) test results.
Results: Of 1449 patients recruited during the 6-month study period, only 44 (3.0%) had positive throat cultures for group A beta-haemolytic streptococcus. The majority of group A beta-haemolytic streptococci were isolated from patients between the age of 3 and 60 years. Clinical findings other than an absence of cough were found to be unhelpful in predicting group A beta-haemolytic streptococcal throat infection. The sensitivity of the rapid group A streptococcal antigen detection test was 52.6% and the specificity was 98.2%.
Conclusions: The prevalence of group A beta-haemolytic streptococcus in patients presenting with a sore throat, or suspected clinically of having acute pharyngitis, was low. If empirical antibiotics were given to all such patients, 97% of them would be unnecessarily treated. Age and absence of cough were the only clinical findings helpful in predicting the presence of group A beta-haemolytic streptococcal throat infection. The rapid group A streptococcal antigen detection test can provide a quick guide to clinicians on the necessity of antibiotic therapy. However, a confirmatory throat culture backup is recommended for patients with a negative test result.