The Widal and Weil-Felix tests are primarily used to detect which substances?

The Widal and Weil-Felix tests are specifically designed to detect febrile agglutinins, which are antibodies produced in response to certain bacterial infections. The Widal test is used mainly for diagnosing typhoid fever caused by Salmonella typhi, while the Weil-Felix test is used to identify infections caused by Rickettsial organisms through cross-reactivity with certain strains of Proteus bacteria.

In both tests, the presence of agglutinins indicates a significant immune response against these specific pathogens, making febrile agglutinins critical for the diagnosis of associated diseases. By measuring the agglutination of bacteria in the presence of serum containing these antibodies, clinicians can infer the presence of an ongoing infection.

The other options do not relate to the specific function or purpose of these tests. Autoantibodies are associated with autoimmune diseases and are not the target of either Widal or Weil-Felix tests. Testing for pathogen DNA typically requires molecular techniques, such as PCR, which is unrelated to the agglutination assays of the Widal and Weil-Felix tests. Inflammatory cytokines are measured through different types of assays aimed at evaluating the immune response, but they are not the focus