Determining clinical significance in repeated laboratory measurements. The "Clinical Delta Range"

A study of healthy subjects was conducted at the University of Florida wherein 52 routine clinical laboratory procedures were measured durng normal operation of the clinical laboratories. The goal of the study ws to quantify nonsignificant personal variation for a number of laboratory procedures referred to as a "Clinical Delta Range," which results from taking several samples per day, several days during the week. Results of the statistical test of hypotheses are given together with summary statistics for the 52 different laboratory procedures. A discussion of the model and testing methods are provided. Further, examples are given to illustrate the methodology and certain limitations associated with the concept of a Clinical Delta Range.