Group A Streptococcus, commonly known as strep throat, is a bacterial infection that can cause a sore throat and other symptoms. This condition requires accurate and timely diagnosis to prevent potential complications. Understanding when to seek testing and what the results signify helps ensure appropriate management.
Recognizing Symptoms That Warrant a Strep Test
Strep throat often presents with a sudden sore throat, making swallowing painful. Fever and red, swollen tonsils are common. White patches or streaks of pus on the tonsils, and tiny red spots (petechiae) on the palate, can also be present.
Unlike a common cold, strep throat typically lacks a cough, runny nose, or hoarseness. Headache, stomachache, nausea, or vomiting, especially in younger children, can also occur. These signs help distinguish strep throat from common viral infections, prompting consideration for testing.
Optimal Timing and Methods for Strep Testing
Testing for strep throat is most effective when symptoms are present, ideally within 24 to 48 hours of onset for accurate results. Two primary methods are used for diagnosis: the Rapid Strep Test (RST) and a throat culture. The RST provides quick results, often within minutes, by detecting specific Group A Streptococcus antigens. While convenient, RSTs can sometimes produce false negatives, meaning the test is negative even if the infection is present.
A throat culture offers a more definitive diagnosis for confirming strep throat. For this test, a throat swab sample is sent to a laboratory where it is cultured to allow any bacteria present to grow. Results typically take 24 to 48 hours to become available. Throat cultures are often performed to confirm negative rapid test results, especially in children, given the higher risk of complications from untreated strep in this age group.
Interpreting Strep Test Results and Next Steps
A positive strep test result confirms Group A Streptococcus. In such cases, antibiotic treatment, commonly penicillin or amoxicillin, is typically prescribed. It is important to complete the full course of antibiotics, even if symptoms improve, to prevent serious complications.
Untreated strep throat can lead to conditions such as rheumatic fever, which can affect the heart, or post-streptococcal glomerulonephritis, a type of kidney inflammation. Individuals usually become non-contagious and can return to school or work about 24 hours after starting antibiotics, provided their fever has subsided.
Conversely, a negative strep test result suggests that strep throat is unlikely to be the cause of the symptoms. If symptoms persist or worsen after a negative rapid test, particularly in children, a follow-up throat culture might be recommended to rule out a false negative. Most sore throats are caused by viral infections, which do not respond to antibiotics and typically resolve on their own.