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Purpose of the test

  1. To diagnosis,  exposure to Streptococcal infection.
  2. To diagnose streptococcal diseases like glomerulonephritis, rheumatic fever, bacterial endocarditis, and scarlet fever.
  3. Significant level was seen in glomerulonephritis and rheumatic fever.




  1. Streptolysin O is an extracellular toxin produced by many of the streptococci group, particularly by group A β-hemolyticus streptococci.
  2. The Streptolysin O enzyme is antigenic and immune system will produce antibody as Antistreptolysin O antibody ( ASO ).


  1. ASO appear in the serum after one week to one month of streptococcal infection.
  2. ASO has no value for the diagnosis of acute streptococcal infection.
  3. The serial rising titer of ASO over weeks and followed by a slow fall in titer is more significant for streptococcal infection.
  4. After 6 months only 30% of the patient show abnormal titer.


ASO is positive in:

  1. Acute streptococcal infections.
  2. Bacterial Endocarditis.
  3. Post-streptococcal glomerulonephritis ( 50 to 70 % of the patients shows no high titer ).
  4. Rheumatic fever
  5. Scarlet fever
  6. ASO is often not raised in these diseases.

Important Factors

  1. An increased titer may be found in the healthy carrier.
  2. Antibiotic therapy may suppress the antibody response.
  3. Increased Lipoprotein level inhibit Streptolysin O and produce false high ASO titer.

Possible References Used

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