ASO test – indications, standards and result interpretation. When to perform an ASO test?

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The ASO test is most often used in the diagnosis of current and past group A streptococcal infections. Timing of the ASO test is essential because streptococcal diseases are often asymptomatic and, if left untreated, may lead to serious complications. How to interpret the ASO test results?

What is an Dealership?

ASO is an abbreviation for antistrepolysin or antistrepolysin reaction. ASO is an antibody that reacts with streptolysin O. ASO antibodies appear in the bodies of people who have been infected with streptococcus or are carriers of this bacterium. ASO antibodies do not appear in the blood serum of completely healthy people. However, due to the fact that in our daily life, we are often exposed to contact with streptococcus bacteria, the appearance of ASO antibodies in the serum is not surprising, as long as their concentration is within the qualified standard.

ASO examination – indications

The most important indication for an ASO test is if you suspect you have been infected with group A streptococcus. Streptococcus is the bacteria that usually causes angina or scarlet fever. It is extremely important to have an examination and start treatment, as ignoring this infection can lead to myocarditis, glomerulonephritis, and rheumatic fever.

Scarlet fever is most common in children between the ages of 5 and 15. Scarlet fever was once considered a serious childhood disease. She can now be treated with antibiotics, but can also cause complications if left untreated. Symptoms of scarlet fever include:

1. red rash that looks like sunburn;
2. red lines around the groin, armpits, elbows, knees and neck;
3. flushed face with a pale ring around the mouth;
4. red and uneven tongue that may become white early.

Among other problems caused by streptococcus, rheumatic fever can also be mentioned. It is an inflammatory immune response, not an infection, and is not contagious. Doctors believe that this is the body’s immune response to a previous streptococcal infection or scarlet fever. Rheumatic fever is a serious disease that can affect the heart, joints, brain and skin. Symptoms of rheumatic fever can include:

1. painful, tender joints in the knees, ankles, elbows and wrists;
2. fever;
3. heart symptoms such as chest pain, shortness of breath and a fast heartbeat;
4. fatigue
5. uncontrolled seizures;
6. lumps under the skin near joints (although this is rare);
7. a rash of pink rings with a clear center (though this is also rare).

Glomerulonephritis, on the other hand, is a type of kidney disease. Tiny filters in the kidneys called glomeruli are damaged. This can make the kidneys struggle to clear waste and fluid from the body. Serious cases can cause kidney failure. You may not have any symptoms of glomerulonephritis. If he has symptoms, these may include:

1. blood in urine;
2. tiredness;
3. nausea;
4. rash;
5. high blood pressure (hypertension);
6. joint or abdominal pain;
7. passing less urine or urinating more than usual;
8. foamy urine;
9. swelling of the face or joints.

Without proper treatment, streptococcal bacteria can spread to other areas of the body. This can cause infections of the tonsils, sinuses, skin, middle ear, and blood.

ASO testing is recommended after angina, especially when the following symptoms persist:

1. fever;
2. general weakness;
3. palpitations;
4. breathing problems;
5. hematuria;
6. swelling;
7. arthralgia;
8. skin rash;
9. chorea, i.e. the involuntary reflexes of the body.

ASO examination – course

The ASO test is based on a laboratory blood test. The test uses a blood sample taken from the patient, e.g. from a vein in the arm. ASO testing should be performed on an empty stomach, taking into account earlier discontinuation of drugs, including antibiotics and corticosteroids.

Reliable results of the ASO test are most often obtained after the diagnosis is repeated several times, because the immune system produces antibodies within a week to 4 weeks after infection with the streptococcal bacterium. The highest concentration of ASO antibodies occurs about 4-6 weeks after infection. However, the ASO examination itself does not allow to determine whether the patient is at risk of any disease complications after a history of streptococcal infection.

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What are the ASO standards?

As previously mentioned, in people who have never had contact with streptococci, ASO antibodies should not appear in the blood serum. However, most healthy people come into contact with this bacterium, so a certain level of ASO antibodies in the blood may appear on the test.

A proper and correct blood ASO level indicator is 10-200 IU / ml. Values ​​exceeding this result indicate possible streptococcal infection and are a signal for treatment implementation.

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ASO test – interpretation of results

Elevated ASO antibody levels occur when adult test results exceed 250 IU / ml. In children, however, elevated concentrations are said to exceed 330 IU / ml. Usually, high ASO in the blood is associated with symptoms that occur in streptococcal infections.

A negative ASO level or a very low ASO level means that the patient probably has not had a recent streptococcal infection. The body begins to produce ASO antibodies one week to one month after infection. Three to five weeks after falling ill, a person will have the most antibodies in their blood. Then they will start to decrease. ASO antibodies will remain detectable in the blood for several months after infection.

Are there any risks associated with the ASO test?

A blood test carries some risks. These include bleeding, infection, bruising, and feeling light-headed. You may feel a slight prickle or painful feeling when the needle goes into your arm or hand. Later, the injection site may be painful.

ASO examination – cost

If a referral for an ASO examination is issued by a general practitioner or specialist, it is fully reimbursed by the National Health Fund. However, if the patient wants to perform an ASO test privately, the cost of such a test will be within the range of PLN 20-30.

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ASO test – other necessary tests

If your doctor thinks you may currently have strep throat, you may need a throat swab for Streptococcus pyogenes antigen to check for GAS. If you have an infection elsewhere in your body you may need to culture blood, tissue or mucus in your lungs.

If your doctor thinks you may have rheumatic fever, you may need other tests to check for antibodies. Other antibodies that may be present in the blood are anti-dsDNA B or anti-streptolysin antibodies. They can help the doctor determine if the patient has rheumatic fever.