Strep throat is a common bacterial infection caused by Streptococcus pyogenes, also known as Group A Streptococcus (GAS). While many sore throats are caused by viruses, strep requires antibiotic treatment to prevent complications and limit the spread. Accurate and timely diagnosis is important for effective treatment and managing this highly contagious condition.
Key Symptoms Indicating the Need for Testing
Strep throat typically presents with a rapid onset of symptoms, often within one to three days after exposure. The most common sign is a sudden, severe sore throat accompanied by pain or difficulty swallowing. This is frequently paired with a fever of 101°F (38°C) or higher.
A visual examination may reveal swollen, red tonsils with white patches, streaks of pus, or a sandpaper-like rash. Small, pinpoint red spots, known as petechiae, may also be visible on the roof of the mouth. Swollen and tender lymph nodes in the front of the neck are also common accompanying symptoms.
The presence of certain other symptoms makes strep throat less likely and often suggests a viral infection. Strep throat is a bacterial infection and generally does not cause upper respiratory symptoms. A cough, runny nose, congestion, hoarseness, or conjunctivitis (pink eye) typically indicates a viral illness that does not require antibiotic treatment.
Who Should Be Tested (Age and Exposure Considerations)
Testing is recommended for school-age children between five and fifteen years old, as they account for the majority of strep throat cases. Untreated infection consequences are more significant in this demographic, making prompt diagnosis a priority. Anyone who has close or household contact with an infected person should also consider testing if they develop symptoms.
Children under three years old are rarely affected by strep throat and have a low risk of developing serious complications. For this reason, testing is generally not performed on toddlers and infants, even if they have a sore throat. Adults are also less likely to contract strep throat unless they are in frequent contact with school-aged children, such as parents, teachers, or childcare workers.
Individuals who test positive for the bacteria but show no symptoms are considered carriers. Asymptomatic carriers are less likely to spread the bacteria or develop complications. Therefore, routine testing is typically not recommended for people without symptoms, and testing is reserved for those who present with characteristic signs of infection.
The Testing Procedure and Interpreting Results
Once a healthcare provider suspects strep throat, they use a simple, non-invasive procedure to collect a sample for testing. A sterile cotton swab is gently rubbed across the back of the throat and tonsils to collect secretions. This sample is then used for one of two main laboratory tests.
The first is the Rapid Strep Test (RST), which provides results quickly, often within ten to twenty minutes. The RST detects antigens from the Group A Strep bacteria and allows for immediate treatment if positive. However, the RST has lower sensitivity, meaning it can sometimes produce a false negative result, especially in children.
Due to the possibility of a false negative, a throat culture is often performed as a follow-up test, particularly for children and adolescents. The culture involves sending the swab to a laboratory, where the sample is grown to see if the bacteria multiply. This test is more accurate and is considered the gold standard for diagnosis, but results take twenty-four to forty-eight hours. A positive result from either test confirms the bacterial infection and warrants the start of antibiotics.
Risks of Delayed Diagnosis
Timely diagnosis and treatment are necessary because an untreated strep infection can lead to serious, non-throat-related complications. These complications are caused not by the bacteria itself, but by the body’s immune response to the infection. The most severe is acute rheumatic fever, which can affect the heart, joints, skin, and brain.
Rheumatic fever can cause permanent damage to the heart valves, leading to rheumatic heart disease. Another potential complication is post-streptococcal glomerulonephritis, which impacts the kidneys. This condition causes inflammation and interferes with the kidney’s ability to filter waste from the blood.
Starting a full course of antibiotics, typically within nine days of symptom onset, prevents the development of acute rheumatic fever. While strep throat symptoms may resolve on their own, antibiotics decrease the risk of systemic complications and prevent the spread of infection. Patients who test positive must complete the entire course of medication prescribed by their doctor.