Practice question

Competitive ELISA excels for low molecular weight haptens and subtle concentration variations because signal is inversely proportional to analyte and competition amplifies small differences. Limited antibody sites create steep competition curve around IC50, so slight rise in sample antigen displaces labeled competitor measurably. Sandwich formats depend on two epitopes and are better for larger proteins but suffer less resolution at low range because excess antigen increases signal linearly. Direct and indirect formats lack competition step and are less sensitive to minor changes. Hence for steroid hormones, toxins and drug monitoring, competitive design provides superior discrimination of minute differences.