Quality Assurance comprises everything that the laboratory does to assure a high quality service to its users. There are two kinds of process, Internal Quality Control (IQC) and External Quality Assessment (EQA).

Each day laboratories analyse IQC materials with known concentrations of specific substances to ensure, in real time, that they are producing reliable results. They also participate in externally organised quality assurance schemes, which provide materials for analysis on a regular basis and without telling the laboratory the results expected.

These schemes provide independent, objective data on individual laboratory and test method performance, and can help laboratories identify problems by comparing their performance with others using the same or different methodology.

Laboratories have comprehensive quality assurance programmes to ensure that every step of the process of producing results – requesting, sampling, analysing and reporting – is monitored to ensure the correct tests are performed, that reliable results are produced, and that these are communicated to the appropriate doctor in a timely manner.

While not infallible, each laboratory's QA programme rigorously defines requirements for staff proficiency, equipment maintenance and monitoring, and other standards of operations. In addition to following their own in-house guidelines, laboratories are monitored by professional accrediting organisations [See Laboratory accreditation - the basis for confidence].