What laboratory test is commonly used to diagnose streptococcal throat infections?

The rapid antigen detection test is commonly used to diagnose streptococcal throat infections due to its speed and specificity in identifying the presence of Group A Streptococcus (Streptococcus pyogenes) in throat swab specimens. This test functions by detecting specific antigens related to the bacteria, allowing healthcare providers to quickly confirm a diagnosis and begin appropriate treatment if necessary. The test can yield results in a matter of minutes, making it a practical choice in clinical settings where prompt intervention is important, especially to prevent complications such as rheumatic fever.

Other tests such as a complete blood count, chest X-ray, and urinalysis do not directly diagnose streptococcal throat infections. A complete blood count can indicate the presence of infection generally, but it is not specific to streptococcal bacteria. A chest X-ray is useful for evaluating respiratory conditions but would not help in diagnosing throat infections. Urinalysis is primarily used to assess kidney function and detect urinary tract infections, making it irrelevant for diagnosing a throat infection caused by streptococci.