This test detects an antibody known as ASO, or anti-streptolysin O. This antibody appears when a person has certain bacteria in the blood. The bacteria are Group A streptococcus, which make an enzyme called streptolysin O. This enzyme destroys red blood cells.
This test can be used to: confirm a recent or ongoing infection with Group A streptococcushelp diagnose rheumatic fever or a streptococcal infection in the kidneysdistinguish whether a person has rheumatic fever or arthritis from another cause
To do the test, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into the vein chosen and the tourniquet is removed. Blood flows from the vein through the needle. It is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
A person should request specific instructions from his or her healthcare professional.
Test results report the number of Todd units of antibodies per milliliter of blood. Normally, ASO antibody levels are less than 160 Todd units per milliliter.
Higher-than-normal levels of ASO antibodies may indicate: scarlet fever, a streptococcal infection involving the throat and tongue that causes fever, rash and rapid pulseother active or previous streptococcal infectionbacterial endocarditis, an inflammation in the lining of the heartpost-streptococcal glomerulonephritis, an infection in the kidneyrheumatic fever, a disease that may affect the heart and kidneysscarlet fever, an infection involving the throat and tongue that causes fever, rash, and rapid pulse
Tabers Cyclopedic Medical Dictionary, F.A.Davis, 1993
Illustrated Guide to Diagnostic Tests, Springhouse, 1998
Mosby's Manual of Diagnostic and laboratory Tests, Kathleen Pagana and Timothy Pagana, 1998