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About the test
What is this test done for?
ASO titer or antistreptolysin O titer, is a blood test that measures the antibodies against streptolysin O, a substance produced by bacteria belonging to Streptomycin group A.
Why is it Done?
This is a special blood test that checks for antibodies prepared against Streptomycin group A bacteria. This happens in response to infection caused by Group A Streptococcus bacteria.The test is done for identifying diseases like
  • Bacterial endocarditis
  • Glomerulonephritis
  • Rheumatic fever
  • Scarlet fever
  • Strep throat
When should it be performed?
This test is performed when a patient
  • Presents with symptoms of rheumatic fever
    • Fever
    • Joint pains, mostly knees, ankles, elbows, wrists
    • Joints are red and swollen
    • Painless small bumps under the skin
    • Chest pain
    • Fatigue
    • Jerky, uncontrolled movements of hands, feet, and face
  • Presents with symptoms of glomerulonephritis
    • Facial puffiness
    • Low urine production
    • Blood in urine
    • Collection of fluid in lungs
    • High blood pressure
  • Presents with symptoms of endocarditis
    • Fever
    • Chest pain
    • Red skin rash
    • White spots in mouth or tongue
    • Shortness of breath
    • Headache
    • Muscle aches and tenderness
    • Pain and swelling of joints
  • Presents with symptoms of Scarlet fever
    • Red rash like sun burn on trunk, arms, and legs
    • Flushed face
    • Tongue looks red and bumpy, like strawberry
    • Fever
    • Sore throat
    • White or yellow patches on throat
    • Difficulty in swallowing
    • Nausea or vomiting
How is it done
A blood sample will be collected from a vein in your arm. No special precautions like fasting required.
The test result is normal, if levels are below200 IU/L. It means
  • No group A streptococcus infection
The test results are abnormal, if levels are above200 IU/L. It means
  • Group A streptococcal infection
  • Post-streptococcal infection complications
  • Rheumatic fever
  • Rheumatic heart disease
  • Glomerulonephritis
  • Endocarditis
  • Scarlet fever
Other Tests
  • CBC
    • Increased WBC count indicates infection
  • Blood culture
    • Growth of streptococcus bacteria in blood culture indicates streptococcal infection
    • It even helps in identifying the antibiotic medicine of choice for the treatment
  • Anti DNase B test
    • It is a highly specialized blood test that helps to evaluate prior streptococcal infection
    • Positive test indicates streptococcal infection
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