Biological day-to-day variability and critical differences in the serial measurement of two markers of bone turnover in the sera of healthy young males. National

The study outlined here is part of an overall project, which aims to identify the optimum marker of bone resorption for both healthy young males and post-menopausal, non-osteoporotic women, and is as yet ongoing1. The purpose of this investigation was to quantify the biological day-to-day variability in serum levels of N-Mid Osteocalcin (OC; ng/ml) and CrossLaps (ng/ml) in healthy males (n=14). From this biological variation (CVi: individual biological variability), the critical difference (CD) or least significant change was calculated as previously described2. This value represents the minimal difference between two measurements of a biochemical marker that indicates a medically significant alteration of homeostasis (and is not due to normal biological and/or analytical variability alone). Given the CD of these markers the viability of using them in the assessment and/or monitoring of bone metabolism will be considered.