Clinical Health Updates

Rapid antigen test reduces antibiotic use in adult sore throat

Clinical Question:
What is the best strategy for diagnosing strep throat in adults?

Bottom Line:
The use of a rapid antigen test reduces antibiotic use in adults with sore throat better than usual care and better than the use of a clinical decision rule alone. A combined approach using a clinical decision rule plus a rapid antigen test when the clinical rule is equivocal may be the most efficient approach.

Worrall G, Hutchinson J, Sherman G, Griffiths J. Diagnosing streptococcal sore throat in adults: randomized controlled trial of in-office aids. Can Fam Physician 2007;53:666-671.

Study Design:
Randomized controlled trial (nonblinded)

Sore throat is among the most common problems seen in primary care practices, and it is evaluated using a variety of strategies. In this study, 37 Canadian family doctors were asked to recruit 20 successive adults with sore throat. The physicians were randomized to use 1 of 4 strategies: usual clinical practice, decision rule only, rapid antigen test only, and clinical decision rule plus rapid antigen test if the decision rule was equivocal. The clinical decision rule was based on the well-validated Centor rule, with 1 point each for fever, swollen glands, absence of cough, and tonsillar exudate, and 1 point subtracted for presence of cough. Interpretation of the rule was as follows: Antibiotics were not recommended for a patient with less than 2 points; antibiotics were recommended for a patient with 3 or 4 points; and no recommendation was made if a patient had 2 points. Between 102 and 170 patients were recruited into each arm and 47% of all patients received a prescription for an antibiotic. The percentage of visits resulting in an antibiotic prescription was 27% for rapid antigen test alone; 38% for clinical decision rule plus rapid antigen test; 55% for clinical rule only; and 58% for usual practice. The difference between the 2 rapid antigen groups and the usual care group was statistically significant, but the difference between clinical rule plus rapid antigen test and the rapid antigen test alone was not. We are not told how many patients had the rapid antigen test in the combined approach group, but presumably it was fewer than in the group where all patients received rapid antigen testing. We are also not told clinical outcomes such as the percentage of patients cured at 2 weeks or the percentage returning because of treatment failure.