Pharyngitis is mostly of viral etiology; Strep Throat Score used for evaluating probability of group A strep (GAS) etiology (sensitivity 83.1%, specificity 96.9%)
Tonsillar swelling or exudate (1 pt)
Tender anterior cervical nodes (1 pt)
Absence of cough (1 pt)
Temperature >38°C (1 pt)
Age 3-14 (1 pt); Age 15-44 (0 pts); Age ≥45 yrs (-1 pt)
Scoring:
1 pt - no culture or antibiotic required (2-6% likelihood of strep)
2-3 pts - culture all and treat only if culture positive (10-28% likelihood)
4 pts - culture, treat with penicillin on clinical grounds (38-63% likelihood).
References
McIsaac WJ, White D, Tannenbaum D, Low DE (1998). A clinical score to reduce unnecessary antibiotic use in patients with sore throat. CMAJ. 158(1):79.