Fluorescent Antibody Titration for Antistreptolysin O (ASO) Antibodies

What Is ASO Antibody Testing Used For?

ASO testing is primarily used to diagnose or confirm a history of Group A Streptococcal infections, such as strep throat or scarlet fever. It can also help evaluate persistent symptoms (like sore throat or fever) that may suggest a past infection, even if initial rapid strep tests were negative.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The serum (liquid part of blood) is then tested using a fluorescent antibody technique to detect ASO antibodies. Results are reported as a titer value, which indicates the strength of your immune response.

When Might You Need This Test?

Your healthcare provider may recommend ASO testing if you have symptoms like persistent sore throat, fever, or rash that suggest strep infection, especially if rapid strep tests were inconclusive. It’s also used in cases of recurrent throat infections or when evaluating complications like rheumatic fever.

What Do the Results Mean?

Elevated ASO levels suggest a recent or past Group A Streptococcus infection. While not always definitive, high titers can support a diagnosis and guide treatment decisions, such as antibiotics to prevent complications.