Strep throat is a common bacterial infection of the throat and tonsils, caused by Streptococcus pyogenes bacteria (Group A Streptococcus or GAS). A sore throat, especially painful when swallowing, is a primary symptom, often with irritated and swollen tonsils. Strep tests identify these bacteria, helping healthcare providers determine if antibiotics are needed, as viral infections can have similar symptoms but do not respond to antibiotics.
Understanding a Positive Strep Test
A positive strep test indicates the presence of Streptococcus pyogenes bacteria in the throat. The two main testing methods are rapid strep tests and throat cultures. Rapid strep tests detect bacterial antigens, providing results within 10 to 20 minutes. A throat culture involves growing bacteria from a swab sample in a lab, taking one to two days for results but offering high accuracy. When symptoms are present, a positive test generally indicates an active infection requiring treatment.
When a Positive Test Might Not Indicate Active Illness
While a positive strep test often points to an active infection, it might not always. Rapid strep tests, though reliable with high specificity (95-99%), can occasionally produce a false positive. This means the test indicates bacteria are present when they are not truly causing illness. Factors contributing to false positives include technical errors during test processing, such as improper swabbing, or the detection of non-pathogenic strep bacteria naturally residing in the throat.
Another common scenario is being a strep carrier. This occurs when Streptococcus pyogenes bacteria are present in an individual’s throat, but they do not experience symptoms. Approximately 12% of asymptomatic school-aged children can be carriers. Carriers have a lower density of S. pyogenes in their pharynx compared to those with active infections, leading to a decreased potential for transmitting the pathogen. While carriers can transmit the bacteria, they do not require antibiotic treatment unless specific situations arise, such as during an outbreak or if they have a history of rheumatic fever.
Next Steps After a Positive Strep Test
Following a positive strep test, consult a healthcare provider to determine the appropriate course of action. If symptoms are present, antibiotics like penicillin or amoxicillin are prescribed to treat the infection. Completing the full 10-day course of antibiotics is important to eliminate the infection, reduce symptoms, limit contagiousness, and prevent potential complications such as rheumatic fever. Children can return to school or daycare after being on antibiotics for at least 12 to 24 hours and once their fever has subsided.
If a positive strep test occurs without symptoms, a healthcare provider might consider a carrier state. In such cases, antibiotics may not be necessary, as carriers are less likely to spread the bacteria or develop complications. Medical advice is important to assess the individual situation, considering symptoms, exposure history, and clinical context, to decide on the management plan.