What is ASO test?

Frequently Asked Questions:

1. What is the ASO test used for?

The ASO test or antistreptolysin O titer test is used to measure the antibodies produced by your body as a response to the group A Streptococcus (GAS) bacteria. Sometimes a strep infection goes undetected because of a lack of symptoms. But it might lead to post-streptococcal complications. To avoid such complications, your doctor conducts the ASO test.

2. Why do I need an ASO test?

Your doctor will advise an ASO test if you exhibit symptoms of post-streptococcal complications. The symptoms of post-streptococcal complications are bacterial endocarditis, rheumatic fever and glomerulonephritis. Your doctor can determine whether you are suffering from post-streptococcal complications by measuring your antistreptolysin antibodies through the antistreptolysin O titer test.

3. What is the ASO test procedure?

Your doctor might advise you to refrain from eating or drinking anything for six hours before the test. During the test, you will have to give a blood sample from the vein of your inner arm. The lab technician will draw your blood through a thin needle and then collect it in a tube. The tube will be sent to the lab to be analysed.

4. What is the normal range of ASO?

The normal range of the ASO test for adults is less than 200. The normal range of the ASO test for children below five years is less than 100. If your results are above normal levels, it indicates you have a post-streptococcal complication. Sometimes if your results are normal but you exhibit symptoms of a post-streptococcal complication, your doctor might recommend a second test.

5. Is fasting required for an ASO blood test?

The ASO test is conducted to measure the level of antistreptolysin antibodies present in your blood to check whether you had a streptococcus infection recently. Your doctor might recommend not eating or drinking anything for six hours before giving a blood sample for the antistreptolysin O titer test.

6. What are the symptoms of ASO positivity?

Some symptoms that ASO positive patients display are:

• Joint swelling and pain
• Fever
• Skin rash
• Heart inflammation (carditis), leading to shortness of breath, chest pain or palpitations.
• Fatigue
• High blood pressure
• Swelling (oedema)
• Painless nodules under the skin

7. How do I prepare for an ASO test?

Your doctor might tell you not to eat or drink anything for six hours before the ASO test. Your doctor might also advise you to stop taking some medicines like corticosteroids before the test. These medicines reduce your ASO antibodies, thereby making it difficult for your doctor to confirm post-streptococcal complications.

8. What are the complications associated with an ASO test?

Although the ASO test is generally safe, it might include certain complications:

• Difficulty in obtaining blood, requiring multiple needle pricks.
• Bleeding after drawing blood from the needle site.
• Infection at the needle site, although rare.
• Blood accumulation or hematoma at the needle site.

9. How to control high ASO titer?

High ASO levels usually indicate a recent streptococcal infection. Controlling a high ASO titer usually involves treating the underlying infection, which may include antibiotics, anti-inflammatory medications, or other therapies to manage symptoms and avoid complications.

10. What does "ASO positive" mean?

A positive result indicates the presence of antistreptolysin antibodies, indicating a recent strep infection. However, if you have an underlying illness, such as rheumatic fever, this test will not detect an increase in antibodies. As a result, in such cases, you may require additional tests to confirm that you have an active infection.

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