The blood test for strep antibodies, also known as the Anti-Streptolysin O (ASO) test, is a diagnostic tool used to detect the presence of antibodies against Group A beta-hemolytic streptococci (GABHS) in the blood. This test is typically used to diagnose and monitor conditions such as rheumatic fever, post-streptococcal glomerulonephritis, and other autoimmune disorders that may be triggered by a streptococcal infection.
What is the Blood Test for Strep Antibodies?
The ASO test measures the levels of antibodies against streptolysin O, a toxin produced by GABHS. When an individual is infected with GABHS, their immune system produces antibodies to fight the infection. The ASO test detects the presence and levels of these antibodies in the blood. The test is usually performed on a blood sample taken from a vein in the arm, and the results are typically available within a few days.
How is the Blood Test for Strep Antibodies Performed?
The ASO test is performed using a laboratory technique called nephelometry or turbidimetry. In this test, a sample of blood serum is mixed with a solution containing streptolysin O, and the mixture is then measured for the amount of antibody present. The results are usually reported in units of measurement, such as IU/mL (international units per milliliter). The reference range for the ASO test varies depending on the laboratory and the individual’s age, but generally, a value above 200 IU/mL is considered elevated.
| ASO Test Results | Interpretation |
|---|---|
| < 200 IU/mL | Normal |
| 200-400 IU/mL | Borderline |
| > 400 IU/mL | Elevated |
Clinical Significance of the Blood Test for Strep Antibodies
The ASO test has several clinical applications. It’s used to diagnose and monitor conditions such as rheumatic fever, which is an autoimmune disorder that can occur after a streptococcal infection. The test is also used to diagnose post-streptococcal glomerulonephritis, a kidney disease that can occur after a streptococcal infection. Additionally, the ASO test can be used to monitor the effectiveness of treatment for these conditions.
Limitations of the Blood Test for Strep Antibodies
While the ASO test is a useful diagnostic tool, it has some limitations. For example, the test may not detect antibodies against all strains of GABHS, and it may not be positive in all individuals with a streptococcal infection. Additionally, the test can be affected by factors such as age, nutrition, and other medical conditions. Therefore, the results of the ASO test should be interpreted in conjunction with other clinical and laboratory findings.
What is the purpose of the blood test for strep antibodies?
+The purpose of the blood test for strep antibodies is to detect the presence of antibodies against Group A beta-hemolytic streptococci (GABHS) in the blood, which can indicate a past or ongoing infection.
How is the ASO test performed?
+The ASO test is performed using a laboratory technique called nephelometry or turbidimetry, which measures the amount of antibody present in a blood sample.
What are the clinical applications of the ASO test?
+The ASO test is used to diagnose and monitor conditions such as rheumatic fever, post-streptococcal glomerulonephritis, and other autoimmune disorders that may be triggered by a streptococcal infection.
