The clinical diagnosis of GAS pharyngitis is difficult to make. The classical clinic signs suggesting streptococcal infection are tonsillar pharyngeal erythema with or without an exudate and tender anterior cervical lymphadenopathy. Other soft findings include malodorous breath, soft palate petechiae, beefy red swollen uvula, and a scarletiniform rash. The most common symptoms in individuals with GAS pharyngitis are sore throat, fever, headache, and abdominal pain especially in children. Because many of the signs and symptoms of GAS pharyngitis are non-specific it now recommended that the clinical diagnosis be confirmed with laboratory tests.
Throat cultures are the conventional gold standard method for confirming the diagnosis.
Rapid antigen-detection tests may be used, but since a negative test does not exclude the presence of GAS, a throat culture should be obtained in this situation. Children who present with a sore throat and a viral like illness do not require a routine throat swab. These would include children who present with coryza hoarseness, cough, diarrhea, conjunctivitis, anterior stomatitis, and discreet ulcerative lesions. Viruses that commonly cause pharyngitis include adenoviruses, entroviruses, herpes viruses, and influenza viruses. GAS is not a common cause of pharyngitis in preschool children and in fact is unusual in children under 3 years of age and extremely rare in children under 2 years of age.