Instrument Measurements in Osteoporosis Clinical Trials: Evaluating the Endpoints

Medical instruments can be used in one of four primary ways: for screening, diagnosis, prognosis, and monitoring the natural history of the disease or therapeutic intervention. Good quantitative endpoints in clinical trials are usually obtained from instruments measuring a physiological parameter that is relevant to the anticipated effect of the molecular entity under investigation, and nowhere is this more apparent than in the field of osteoporosis. The surrogate endpoint of choice, bone mineral density (BMD), is in fact a recognised diagnostic endpoint in its own right in that the World Health Organization (WHO) criterion for defining osteoporosis in an individual is a BMD that is >2.5 standard deviations (SD) below peak bone mass. However, in the arena of clinical trials the choice of endpoint is not as simple as this (see Section 2.3).