Overview
The antistreptolysin O (ASO) titer test is a blood test that checks for a strep infection. When you come into contact with harmful bacteria, your body produces antibodies to defend itself against these bacteria. Your body produces antibodies specific to the bacteria they fight.The ASO titer test measures antibodies produced by your body in response to a toxin known as streptolysin O. Streptolysin O is a toxin produced by group A Streptococcus (GAS) bacteria. Your body makes the antistreptolysin O antibodies when you have a strep infection caused by GAS bacteria.Usually, when you have a strep infection like strep throat, you receive antibiotics that kill the strep bacteria. But some people don’t have any symptoms during a strep infection and may not know they need treatment. When this happens, an untreated infection can lead to future complications. These complications are known as post-streptococcal complications.The ASO titer test can help your doctor determine if you recently had a strep infection by measuring the presence of antistreptolysin antibodies in your blood.
Streptococcal infection
Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Firmicutes. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted.Three different types of streptococci are initially differentiated by their appearance when they are grown on sheep blood agar:
Beta-hemolytic streptococci produce zones of clear hemolysis around each colony.
Alpha-hemolytic streptococci (commonly called viridans streptococci) are surrounded by green discoloration resulting from incomplete hemolysis.
Gamma-hemolytic streptococci are nonhemolytic.
Subsequent classification, based on carbohydrates in the cell wall, divides streptococci into Lancefield groups A through H and K through T (see Table: Lancefield Classification). Viridans streptococci form a separate group that is difficult to classify. In the Lancefield classification, enterococci were initially included among the group D streptococci. More recently, enterococci have been classified as a separate genus but do express Lancefield group D antigens. Some streptococci such as Streptococcus pneumoniae do not express Lancefield antigens.
ASO Test
Antistreptolysin O (ASO) titer is a blood test to measure antibodies against streptolysin O, a substance produced by group A streptococcus bacteria. Antibodies are proteins our bodies produce when they detect harmful substances, such as bacteria.Anti-Streptolysin O Antibody (ASO) test is a sensitive test for recent streptococcal infection. A rise in ASO begins about one week after infection and peaks two to four weeks later. ASO levels do not rise with cutaneous infections. In the absence of complications or reinfection, the ASO level will fall to preinfection levels within 6 to 12 months. Over 80% of patients with acute rheumatic fever and 95% of patients with acute glomerulonephritis due to streptococci have elevated levels of ASO.A negative test result means that you do not have strep infection. Your health care provider may do the test again in 2 to 4 weeks. At times, a test that was negative the first time may be positive (meaning it finds ASO antibodies) when done again.Normal value ranges may vary slightly. Talk to your provider about the meaning of your test results.An abnormal or positive test result means you recently had a strep infection, even if you had no symptoms.Looking for lab test rpr. Use Tuhealthy App to locate quest laboratories near me.
