Sandwich ELISA is the most frequently used immunoassay format for the detection of high molecular-weight antigens (e.g. proteins and peptides). An antibody pair of the capture antibody (immobilized) and detection antibody (in solution) forms a “sandwich“ with a target antigen in between. Both polyclonal and monoclonal antibodies are used. The main features of those immunoassays are high sensitivity and specificity Acetylcholinesterase (AChE), the enzymatic label for enzyme immunoassays, has the fastest turnover rate of any enzymatic label. The use of AChE in ELISA is associated with very low background and an increased signal/noise ratio, wide dynamic range, and versatility.