The publication deals with a brief summarizing the results of a working group of EFLM for biological variation studies (Eu- BIVAS). There are described namely calculations of within- and between subject biological variation and their applications for calculation of analytical quality criteria (APS values) and for calculation of significance of reference changes values as potency for monitoring of the patient's state.
We described EFLM biological variation database. We also show the necessity of biological variation for personalized medicine and individualized approach to laboratory results (individual reference intervals, machine learning).