What is the gold standard test for diagnosing Group A β hemolytic streptococci infection?

• A. Rapid strep test
• B. Nasal culture
• C. Throat culture
• D. Blood test

Answer: (C)

Throat culture is the reference standard for diagnosing Group A β-hemolytic streptococcus pharyngitis because it directly isolates and identifies the organism from the pharynx, providing definitive evidence of infection. The procedure—collecting a swab from the tonsillar areas and posterior pharynx, then culturing on appropriate media to demonstrate beta-hemolysis with confirmation tests—offers high sensitivity and specificity.

While the rapid strep test gives results quickly, it detects GAS antigens and is less sensitive, so a negative result can miss true infections and may require a throat culture to confirm, especially in children. Blood tests aren’t used to diagnose acute GAS pharyngitis, and nasal cultures aren’t reliable for this infection since GAS primarily colonizes the throat.