Objective: To validate a score based on clinical symptoms and signs for the identification of group A Streptococcus (GAS) infection in general practice patients with score throat.
Design: A single throat swab was used as the gold standard for diagnosing GAS infection. Clinical information was recorded by experienced family physicians on standardized encounter forms. Score criteria were identified by means of logistic regression modelling of data from patients enrolled in the first half of the study. The score was then validated among the remaining patients.
Setting: University-affiliated family medicine centre in Toronto.
Patients: A total of 521 patients aged 3 to 76 years presenting with a new upper respiratory tract infection from December 1995 to February 1997.
Outcome measures: Sensitivity, specificity and likelihood ratios for identification of GAS infection with the score approach compared with throat culture. Proportion of patients prescribed antibiotics, throat culture use, and sensitivity and specificity with usual physician care and with score-based recommendations were compared.
Results: A score was developed ranging in value from 0 to 4. The sensitivity of the score for identifying GAS infection was 83.1%, compared with 69.4% for usual physician care (p = 0.06); the specificity values of the 2 approaches were similar. Among patients aged 3 to 14 years, the sensitivity of the score approach was higher than that of usual physician care (96.9% v. 70.6%) (p < 0.05). The proportion of patients receiving initial antibiotic prescriptions would have been reduced 48% by following score-based recommendations compared with observed physician prescribing (p < 0.001), without any increase in throat culture use.
Conclusions: An age-appropriate sore throat score identified GAS infection in children and adults with sore throat better than usual care by family physicians, with significant reductions in unnecessary prescribing of antibiotics. A randomized trial comparing the 2 approaches is recommended to determine the ability of the score approach to reduce unnecessary prescribing of antibiotics during routine clinical encounters.