Streptolysin O is a hemolytic toxin produced by Streptococcus pyogenes.

The body produces ASO antibodies in response to infection.

Clinical uses include:

Detecting recent streptococcal infection (throat or skin).

Supporting diagnosis of rheumatic fever and post-streptococcal glomerulonephritis.

Differentiating streptococcal complications from other causes of joint pain, fever, or kidney disease.

The test is performed using a blood sample, often alongside other streptococcal antibody tests (e.g., Anti-DNase B).

Analyte: Antistreptolysin O (ASO) antibody levels in serum.

Normal Range: < 200 IU/mL (adults); < 400 IU/mL (children; varies by lab).

Abnormal Findings:

Elevated ASO titre: Indicates recent or ongoing streptococcal infection.

Persistently high levels may suggest post-streptococcal complications.

Clinical Use:

Provides evidence of recent streptococcal exposure.

Helps confirm diagnosis of rheumatic fever or glomerulonephritis.

Guides treatment and monitoring in infectious and autoimmune conditions.