The Strep Test is used to test for the presence of beta-haemolytic Group A streptococci in pharyngeal smears.
The infection caused by these microorganisms (Streptococcus pyogenes) is usually easily treatable with antibiotics. If left untreated, the infection can lead to complications, such as rheumatic fever and post-streptococcal glomerulonephritis. Screening for the presence of streptococci is also useful because it allows the physician to avoid unnecessary use of antibiotics for viral infections, thereby reducing the incidence of antibiotic resistance.
The rapid Streptococcus test has a specificity and sensitivity of about 98% and 95%, respectively. The assay is performed using immunochemical methods involving monoclonal antibodies against Group A streptococcal antigens and a pharyngeal smear material is used as a sample. The test can only check for the presence of beta hemolytic Streptococcus Group A. Other causes of pharyngitis and pharyngoamygdalitis cannot be detected with this test.
The diagnosis of pharyngitis from beta hemolytic Group A streptococci should be based on laboratory tests and not clinical tests. The Strep Test is useful but is not sensitive enough to be used alone. The rapid Streptococcus test followed by culture of pharynx and sensitivity test has the highest positive predictive value.
If the test is positive, the patient should start treatment with an antibiotic, such as penicillin, or in the event of an allergy, erythromycin. If the test is negative, a culture and sensitivity test must be performed to determine if the rapid Streptococcus test was false-negative.
The positive result does not distinguish between people with active streptococcal infection and those who are streptococcal carriers.
Possible Interpretations of Pathological Values
- Positive: B-hemolytic Streptococcus infection of group A.
- Negative: Absence of infection, viral infection, false negative result
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.