Standards

Most tests will have a type of standard to measure quality and ensure the result is as accurate as possible. There are usually two types either primary or secondary. A primary standard is of a known quantity and is often produced externally with certification, they are used to characterise the upper and lower parameters or sensitivity of the test. Often labelled as high, low, calibrators, controls they can also be used to calibrate on-board software of automated analysers. They have a clear advantage in that they can be stored long term and provide a known amount or concentration; a clear disadvantage is that they are usually in a “pure” matrix such as saline or a buffer. I’m confident in declaring that there is no human alive with blood constituted from 100% saline. Hence the need for secondary standards which are usually samples of plasma, serum or whole blood to ensure that test is suitable and consistent in the chosen matrix.