ASO (Anti-Streptolysin O) titer
The ASO (Anti-Streptolysin O) titer test is used to evaluate the presence and level of antibodies against streptolysin O, a toxin produced by Group A Streptococcus bacteria. Here’s how the ASO titer test is used:
- Diagnosis of Recent Group A Streptococcal Infection: Group A Streptococcus (GAS) bacteria cause various infections, including strep throat, scarlet fever, and certain skin infections. After an infection with GAS, the body produces antibodies, including anti-streptolysin O antibodies (ASO), as part of the immune response. The ASO titer test measures the level of ASO antibodies in the blood. A significant rise in ASO titer indicates recent or ongoing infection with GAS, particularly if accompanied by clinical symptoms of infection.
- Confirmation of Rheumatic Fever: Rheumatic fever is a complication of untreated or inadequately treated GAS infections, particularly strep throat. In rheumatic fever, the immune system mistakenly attacks healthy tissues, leading to inflammation and damage to the heart, joints, and other organs. Elevated ASO titers are often observed in individuals with acute rheumatic fever. The ASO titer test may be used as a diagnostic tool to support the diagnosis of rheumatic fever, particularly in combination with other clinical findings and laboratory tests.
- Monitoring Treatment Response: The ASO titer test may be used to monitor the response to treatment in individuals with GAS infections or rheumatic fever. A decline in ASO titer levels over time may indicate a favorable response to antibiotic therapy and resolution of the infection or inflammatory process.
- Assessment of Post-Streptococcal Complications: Some post-streptococcal complications, such as acute glomerulonephritis (inflammation of the kidneys), may be associated with elevated ASO titers. Measurement of ASO titers may be helpful in evaluating individuals with suspected post-streptococcal complications and guiding management decisions.
- Population Screening: In certain settings, such as schools or military barracks, screening for GAS infections using the ASO titer test may be performed to identify individuals at risk of spreading infection or developing complications.