Objectives: To identify clinical features that predict Group A streptococcal (GAS) pharyngitis in a Japanese paediatric primary emergency medical centre. Methods: The prevalence of GAS pharyngitis according to age and body temperature (BT) was calculated among 3098 paediatric patients with pharyngitis. The numbers of GAS-positive and -negative patients for each clinical parameter, and each point increase in the McIsaac score were compared and likelihood ratios (LRs) were calculated. Results: The prevalence of GAS pharyngitis was extremely low in patients aged < 1 (1.2%) and 1 year (3.9%). The GAS-positive rate was significantly higher in patients with a BT < 38.0°C compared with ≥ 38.0°C (30.0% vs. 19.8%). A BT ≥ 38.0°C was not a predictive finding for GAS pharyngitis (positive LR: 0.82). Rash was the most useful individual predictor, and a McIsaac score of 4 or 5 increased the probability; however, the positive LRs were 1.74 and 1.30, respectively. Conclusions: The prevalence of GAS pharyngitis is extremely low in patients aged < 1 and 1 year, and a BT ≥ 38.0°C is not a predictive symptom. Although a rash and McIsaac score of 4 or 5 are associated with an increased probability, they cannot be used to confirm GAS infection.
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