The previous section covered the need for standards to obtain quantitative ELISA results. It should be noted that standards should be acquired in sufficient amounts (or a reliable supply needs to be found) not only for the development phase but also for the expected service life of the assay. Additional to standards, controls should be included in ELISAs.
The most basic control is the blank sample control. Additional controls are needed to provide a comparison to real world physiological conditions and a control mechanism for assurance that the assay continues to provide accurate results. Hence control samples that have had their analyte concentration validated by another method are employed. These can be set up as positive, but also as negative controls. A control subcategory is spiked samples; here a known amount of standard has been added to the matrix used for the ELISA. Spiked controls can indicate assay performance by calculating percent recovery from the ELISA readout. When recombinant proteins are used, their equivalent functionality to the endogenous wild type versions of the protein needs to be checked.