Serum Antistreptolysin O (ASO) Antibody, Titration

Why This Test Matters

ASO antibodies appear in your blood after an infection with group A *Streptococcus*. This test is often used to confirm a diagnosis of conditions like rheumatic fever or post-streptococcal glomerulonephritis, which can occur months after an initial infection. It’s not typically used for active strep throat diagnosis, as other tests (like rapid strep swab) are usually preferred.

How the Test Works

Blood is drawn and tested for ASO antibodies using an immunoassay method. The test detects the presence and concentration of these antibodies, which rise shortly after infection and may remain elevated for weeks or months.

What to Expect Before the Test

No special preparation is needed. You may have a slight bruise or soreness at the blood draw site, but this usually fades quickly. If you’re on blood-thinning medication, let your provider know before the test.

What to Expect After the Test

You can return to your normal activities immediately. Apply gentle pressure to the site to stop bleeding, and avoid vigorous activity for a few hours. Call your provider if you experience excessive bleeding, swelling, or signs of infection (e.g., fever, redness, or pus).