Immunoassays: Tools for Sensitive, Specific, and Accurate Test Results

Immunoassays are popular in the clinical laboratory because they can quickly and easily provide precise and accurate test results. We review the principles of immunoassays with emphasis on the advantages of the two basic types (competitive vs noncompetitive). We address the methods for distinguishing bound from unbound fractions (homogeneous vs heterogeneous immunoassays) and discuss specific labels for signal generation and detection. Special cases of immunoassays not requiring specific labels are reviewed briefly. Finally, examples and illustrations of commonly used automated immunoassays are provided. This is the third part of a continuing education series on chemistry. Other articles focus on rapid immunoassays, immunosensors, and prostate-specific antigen. After reading this article, participants should be able to distinguish competitive from noncompetitive immunoassays, understand the differences between homogeneous and heterogeneous immunoassays, and identify popular, automated immunoassays.