In immunodiagnostics, how does a Western blot complement ELISA?

• A. It detects specific proteins separated by electrophoresis, providing confirmatory specificity after an initial ELISA.
• B. It replaces ELISA as the primary screening test.
• C. It measures nucleic acids rather than proteins.
• D. It is used only for quantifying cytokines.

Answer: (A)

Western blot adds confirmatory specificity by separating proteins with electrophoresis, transferring them to a membrane, and probing with patient antibodies to reveal which individual proteins are recognized. This pattern shows whether the antibodies detected by the screening ELISA are directed at specific, defined proteins, reducing false positives that can occur with a single ELISA. ELISA is excellent for broad sensitivity and high-throughput screening, but its results can be ambiguous due to cross-reactivity; the Western blot’s protein-by-protein readout provides a more definitive confirmation. It does not replace ELISA as the initial test, does not measure nucleic acids, and is not used solely for cytokine quantification.