Rationale and public health implications of changing CHD risk factor definitions.

The definition of disease is central to the practice of medicine and to public health policy. Practice guidelines set standards for disease identification and treatment. Quality care is often defined as adherence to these guidelines. Over the past few years, the diagnostic thresholds for several common medical conditions have been lowered, resulting in a substantial expansion in the market for health care. The most recent guidelines for high blood pressure, high cholesterol, and impaired fasting glucose each define a high percentage of the adult population as in need of regular medical attention. Under the latest proposed thresholds, virtually the entire adult population qualifies for a chronic condition diagnosis. We evaluate the health and financial outcomes associated with changes in diagnostic thresholds for the prevention of three risk factors for cardiovascular disease and stroke: blood pressure, serum cholesterol, and fasting plasma glucose. Estimates of the numbers of people affected, the cost implications, and the overall public health consequences are offered.