Antistreptolysic (ASO)

Latest Edit: Hector 2014-03-21 (EDT)

See Also	Lab Tests

This test is used mainly to determine whether a previous streptococcus infection has caused a poststreptococcal disease, such as glomerulonephritis, rheumatic fever, bacterial endocarditis, and scarlet fever.

Discussion

• ASO, or antistreptolysic O titer is a seroligic procedure that shows the body's reaction to infection caused by group A beta-hemolytic streptococci.
• Streptococcus organisms produce an enzyme called streptolysin O, which can destroy red blood cells.
• Therefore, the body reacts to the antigenic streptolysin O by producing ASO, a neutralizing antibody.
• ASO can appear in the serum 1 week to a month after the onset of a streptococcal infection, levels appearing higher in glomerulonephritis and rheumatic fever.

Patient Preparation

• No fasting required.

• Factors which can cause increased levels

• Increased beta-lipoprotein levels can neutralize streptolysic O and appear as increased ASO levels

• Factors which can cause decreased levels

• Drugs: antibiotics and adrenocorticosteroids

Clinical Implications

High levels indicate:

• Acute streptococcal infection
• Acute rheumatic fever
• Bacterial endocarditis
• Acute glomerulonephritis
• Scarlet fever
• Streptococcal pyoderma

Associated Tests

• Antideoxyribonuclease-B Titer