What laboratory test is used to support the diagnosis of rheumatic fever?

The test that is most relevant for supporting the diagnosis of rheumatic fever is the antistreptolysin O (ASO) titers. This test measures the levels of antibodies against streptolysin O, a toxin produced by Group A Streptococcus bacteria, which are responsible for causing throat infections that can lead to rheumatic fever as a serious complication. An elevated ASO titer indicates a recent streptococcal infection, which is a key factor in the pathogenesis of rheumatic fever.

In the context of this condition, the presence of elevated ASO antibodies helps confirm that there has been exposure to the causative bacteria and can support the clinical diagnosis when symptoms of rheumatic fever are present. Other laboratory tests, while they may provide supportive information or indicate inflammation or infection, do not specifically confirm the relationship between streptococcal infection and the development of rheumatic fever as directly as the ASO titers do.