Describe how the assays works The pregnancy strip has 3 regions: 1) mouse monoclonal antibody (ab) to HCG- coupled to an enzyme (not attached to strip) 2) immobilized polyclonal ab to HCG- has dye/substrate to enzyme 3) immobilized anti-mouse ab + dye/substrate The strip is dipped in urine closest to region 1. The urine moves up the strip to this region.