What is the primary purpose of serology testing in infectious disease?

• A. Detect host antibodies against pathogens using assays such as ELISA, indirect immunofluorescence, or Western blot.
• B. Detect pathogen antigens in patient samples.
• C. Measure T cell proliferation to an antigen.
• D. Quantify cytokine levels in serum.

Answer: (A)

Detecting antibodies produced by the patient in response to a pathogen is the main goal of serology in infectious disease. By measuring these antibodies in serum, labs can determine if someone has been exposed to a microorganism, whether a current or recent infection is present, or if the person has protective immunity from vaccination. Assays like ELISA, indirect immunofluorescence, and Western blot are used to detect and sometimes quantify these specific antibodies, providing evidence of immune recognition of the pathogen. Serology is especially helpful when direct detection of the pathogen is difficult or when assessing past exposure or immune status. It does not measure the pathogen directly (antigen detection would be the approach there), nor does it assess cellular responses like T cell proliferation or cytokine levels, which are separate aspects of the immune response.