Reference intervals.

Recommended elements of a process for establishing a reference interval: Define the analyte (measurand) for which the reference interval is being established, the clinical utility, biological variation and major variations in form. Define the method used, the accuracy base, and analytical specificity. Define important pre-analytical considerations together with any actions in response to the interference. Define the principle behind the reference interval (i.e. central 95% etc.). Describe the data source(s), including: number of subjects, nature of subjects, exclusions, pre-analytical factors, statistical measures, outliers excluded and analytical method. Define considerations of partitioning based on age, sex etc. Define the number of significant figures, i.e. the degree of rounding. Define the clinical relevance of the reference limits. Consider the use of common reference intervals. Decision and implementation.