Which statement about rapid antigen detection tests for GABHS pharyngitis is true?

• A. It is highly sensitive but not specific
• B. It is highly specific but not sensitive
• C. A negative result rules out GABHS
• D. It has no role in management

Answer: (B)

Rapid antigen detection tests for GAS pharyngitis are designed to quickly identify the presence of Group A Streptococcus antigens and have high specificity but less than perfect sensitivity. This means a positive test almost always confirms GAS infection, so you can confidently start antibiotics right away. However, because sensitivity is not 100%, a negative result does not completely rule out GAS; some infected patients will be missed. Therefore, in cases with high clinical suspicion—especially in children—a throat culture may be used to confirm a negative RADT. In short, a positive RADT is reliable, while a negative RADT may require further testing depending on the clinical context.