Multiple Patient Samples of an Analyte Improve Detection of Changes in Clinical Status

Abstract

Abstract Context. When comparing results over time, biologic variation must be statistically incorporated into the evaluation of laboratory results to identify a physiologic change. Traditional methods compare the difference in 2 values with the standard deviation (SD) of the biologic variation to indicate whether a “true” physiologic change has occurred. Objective. To develop methodology to reduce the effect of biologic variation on the difference necessary to detect changes in clinical status in the presence of biologic variation. Design. The standard test for change compares the difference between 2 points with the 95% confidence limit, given as . We examined the effect of multiple data pairs on the confidence limit. Results. Increasing the number of data pairs using the formula , where n = number of data pairs, significantly reduces the difference between values necessary to achieve a 95% confidence limit. Conclusions. Evaluating multiple paired sets of patient data rather than a single pair results...