What bodily fluid is primarily assessed in the ASO test?

The ASO (Antistreptolysin O) test primarily assesses serum as its bodily fluid. This test measures the level of antibodies produced by the immune system in response to an infection caused by Group A Streptococcus bacteria. When a person is infected, the body produces ASO antibodies, and the serum is the fluid component of blood that contains these antibodies.

Collecting serum is standard practice for such tests because it provides a clear sample in which the antibodies are present and allows for accurate quantification of ASO levels. Utilizing serum ensures that any antibodies produced as a result of streptococcal infection can be reliably detected, as it reflects the systemic immune response to the pathogen.