In ELISA, what is a standard curve used for?

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In ELISA, a standard curve is used to translate the measured signal into a concentration by comparing it to known standards. You run several samples with known concentrations of the target and plot their signals (often absorbance) against those concentrations. This curve provides a quantitative mapping, so the signal from an unknown sample can be interpolated to its concentration, staying within the assay’s reliable range. The curve is typically fitted with a sigmoidal model (such as a four-parameter logistic curve) to enable accurate interpolation.

This approach is distinct from a calibration blank, which establishes zero signal, or from a graph of patient results used to set reference ranges, or from a curve relating incubation time to signal, which would describe a kinetic or time-response relationship rather than quantification of concentration.