Doctors and patients trust that medical laboratory diagnostics always provide the same answers, regardless of when or where a measurement is taken. The SKML contributes to this by sending identical unknown materials to the participating laboratories and asking them to examine them as they do with patient materials. This is called external quality assurance because it takes place next to the internal quality assurance with which each laboratory monitors the consistency of its own quality.

After the participating laboratories have sent their results and conclusions to the SKML, the SKML creates a report for the participants in which they see their results compared with those of other participants and, where available, also those of reference laboratories or other experts. The participating laboratories use the reports as a control and improvement instrument. Experience shows that by participating in external quality assurance programs, the laboratories perform better and therefore the differences between laboratories become smaller.

Through more than 130 schemes, the SKML contributes to the quality of the pre-analytical, analytical or post-analytical phase of laboratory research.