Why does Miltenyi Biotec calibrate cytokine activity assays using the NIBSC standard?

The ED50 value and units/mg determined by an assay are only valid for that respective assay. Even minor variations in the assay conditions can result in a different activity. ED50 value and units/mg determined by different assays usually result in completely different values and cannot be compared. This can only be overcome by calibration of the assay with a defined standard, a reference cytokine with an approved activity. This standard is measured in our assay, and we adjust the assay conditions to measure exactly the activity stated by NIBSC (= assay calibration). As a result, the measured activity of our cytokines is not dependent on the assay and assay variations anymore. It should be kept in mind that activity values from different suppliers are only comparable when such a standard is used in all assays.