Examinations
Examinations
Antistreptolysin O (ASO) is a laboratory test used to detect the presence of streptolysin, a toxin secreted by hemolytic streptococcal bacteria. Group A beta-hemolytic streptococcal infection spreads from person to person through airborne droplets containing secretions from the mouth and throat, such as sneezing and coughing. These infectious droplets can linger in the air for a long time, transmitting the bacteria and causing infections in others.
Although Group A beta-hemolytic streptococcal infection mainly causes strep throat, in some cases, it can also lead to acute glomerulonephritis, acute rheumatic fever, pharyngotonsillitis, impetigo, and gangrenous pyoderma.
Understanding the ASO Test
The ASO test helps determine whether a person has been infected with Group A beta-hemolytic streptococcus. However, it does not distinguish between a past or an active infection. In acute infections, ASO levels double in laboratory tests compared to the recovery phase.
Importantly, ASO levels do not always rise equally in all streptococcal infections. The test is particularly useful for detecting throat infections, but skin infections caused by streptococcus may not always lead to a significant ASO increase. Therefore, the ASO test should be repeated at least twice, several weeks apart to confirm infection.
Sample: Venous blood
Pre-test recommendations:
- Fasting for 8–14 hours before the test is recommended.
- The test can also be taken 4 hours after a light meal.
- Avoid psycho-emotional and physical stress before the test.
- Alcohol consumption should be avoided before the test.
Symptoms of Group A Beta-Hemolytic Streptococcal Infection:
- Sore throat
- Fever
- Stomach pain
- Headache
- Swollen lymph nodes and tonsils
- White inflammatory patches on the tonsils
- Loss of appetite
- Nausea and vomiting
- Difficulty swallowing due to throat pain
- Tonsillitis
- Skin redness, peeling, swelling, or fever
What Does a High ASO Level Indicate?
Hemolytic streptococcus contains an antigen called streptolysin-O, which has toxic effects when it enters the body. ASO (Antistreptolysin-O) is the antibody produced by the immune system in response to streptolysin-O.
The ASO test measures the amount of these antibodies in the blood. A high ASO level suggests the presence of Group A beta-hemolytic streptococcus in the body.
- ASO levels start rising 1–3 weeks after bacterial exposure.
- After treatment, ASO levels remain elevated for 6–12 months.
- If left untreated, Group A beta-hemolytic streptococcal infection can lead to serious complications such as joint diseases, kidney disorders, and heart conditions.