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.
Doctors order the ASO titer test if you have symptoms of post-streptococcal complications.
Generally, an ASO test value below 200 is considered normal. In children under the age of 5, the test value should be less than 100.
