Biological Homogeneity and Precision of Measurement: The Boundary Conditions for Normal in Body Composition

Abstract

For body composition measurements to come of age in clinical medicine, three requirements must be met. The principle measurements must be accurate to a well-defined precision; they must be repeatable in several, preferably in many laboratories who speak a common language; and they must be related to a well-defined range of normal for the particular population being studied. Recent improvements in measurement precision and recent efforts to characterize populations now permit, indeed require, that we consider the third of these mandates with the same intensity that has produced solid accomplishments for precision and accuracy of measurement. The present challenge is to go beyond the research mission: our measurement precisions, combined with the relevance of what we can measure, guarantee our advent to the bedside. Once there, the obligation to define “normal” also comes of age. It is timely to summarize what has been accomplished for accuracy and precision for each of our measurements, and from this position, to decide how we should define “normal” for each component. We may then proceed to the bedside with a frame of reference.