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ASO titer

Also called: Antistreptolysin O, Anti-DNase B

The ASO titer shows a recent strep infection. It helps diagnose complications like rheumatic fever and a kidney inflammation that can follow strep.

SampleA small tube of blood from a vein in your arm
Fasting?Usually not needed
ResultsSeveral days
Good to knowOne result rarely tells the whole story. Your provider looks at your results together with your symptoms, exam, and other tests.

What the test is

It doesn't diagnose current strep throat; a throat swab does that.

Why it's done

  • Joint pain, fever, or heart symptoms after strep
  • Dark urine or swelling after strep

Getting ready and what happens

  • No preparation is needed.

How the test is done

  • A health worker cleans the skin, puts a band around your arm, and draws blood from a vein with a small needle. It takes a few minutes.

What the results mean

High or rising

Shows a recent strep infection, supporting a strep-related complication.

Questions to ask your provider

  • What do my results mean for me?
  • Do I need to repeat this test or have other tests?

Risks

A blood draw is very safe. You may have slight pain or a small bruise where the needle went in.

Related conditions

Related tests

Sources

Last updated 2026-11-13.