Laboratory Antigen Excess

Antigen excess (also known as “prozone” or “hook effect”) occurs when antigen is present in such high levels that it limits the antigen-antibody crosslinking, resulting in the formation of smaller immune complexes causing immunoassays to underestimate high concentrations of protein (see figure below)

Where the physiological measuring ranges are large e.g. serum Freelite, values can range from less than 1mg/L to greater than 10,000mg/L, antigen excess is more likely.