An interpretation of normal ranges based on a new concept "individual difference quotient" of clinical laboratory...

This article presents a new interpretation of so-called clinical normal ranges which have recently been shown to have a wide range in comparison to the narrow individual physiological fluctuations, based on a newly introduced concept "individual difference quotient" of clinical laboratory data. This quotient is defined as the ratio of inter- or intra-individual dispersion within the framework of a random-effects one-way analysis of variance model and can be used as a useful criterion to compare the degrees of individual differences of clinical laboratory tests with different measurement units. Further, as a function of this quotient the probability that a test result for a specific person falls within the normal range of this person can be derived. The derived probability can be expected to play a significant role in assessing an individual's state of health.