ASO (antistreptolysis) are antibodies that block the action of one of the streptococcal enzymes (streptolysin O). The ASO test is used to confirm a history of streptococcal infection (streptococcal angina) and in the diagnosis of rheumatic disease.

TestASOis a serumbloodtest to detect ongoing or recentgroup A streptococcal infection ( Streptococcus pyogenes ), which is one of the most common causes, incl. acute pharyngitis, skin infections, tonsillitis (tonsillitis), pneumonia and scarlet fever. In addition, 10 out of 80 serotypes of streptococcus have rheumatogenic properties, i.e. infection with them may cause rheumatic disease. ASO testing is particularly useful in the diagnosis of acute endocarditis, streptococcal toxic shock, acute rheumatic fever, and acute glomerulonephritis. The clinical sensitivity of the test is 50-80 percent.

When ASO tests are performed

  • to determine if we are dealing with a recent group A streptococcal infection ( Streptococcus pyogenes )
  • to recognize complications such as rheumatic disease or glomerulonephritis after a previous streptococcal A infection

ASOs appear in the blood serum during streptococcal infections. Streptolysin "O" is a fairly potent antigen that triggers the formation of antistreptolysins in an infected human. The presence of antistreptolysins in the blood serum is the basis of the antistreptolysin reaction, a serological test of great importance in the diagnosis of streptococcal diseases. The blood for testing is taken from a vein in the arm. The level of antistreptolysin O in the blood above 200 I is considered significant.

What does a negative test result mean?

A negative test result or a very low concentration of ASO antibodies means that the patient probably has not recently had a group A streptococcal infection, especially when both samples obtained are negative or the amount of ASO antibodies is minimal.

What does too high ASO antibody level mean?

ASO antibodies appear in the serum 7-21 days after infection with streptococcus, with the highest concentration recorded in 3 to 6one week after infection. Hence, a high or rising ASO antibody level indicates a high probability of ongoing Group A Streptococcal infection. A high ASO antibody level, which then declines, indicates a previous infection that is resolving.

Important

About 20 percent of patients are unable to produce measurable amounts of ASO, and about 5 percent of he althy people have ASO levels consistently elevated.

Category:

Research