Glycated haemoglobin and metabolic control of diabetes mellitus: external versus locally established clinical targets for primary care.

OBJECTIVES: To examine current targets for glycated haemoglobin as a marker for metabolic control in diabetes mellitus in relation to datasets from several areas, and to consider whether target setting could be improved.
DESIGN: Data collected from enhanced care records of general practices for a representative community based sample of people with diabetes. SETTING AND
SUBJECTS: 3022 people with diabetes on the lists of 37 general practices (total list size 222,550) in South Glamorgan in 1992; samples of glycated haemoglobin had been processed at two laboratories with different methodologies and reference ranges. MAIN OUTCOME MEASURES: Last glycated haemoglobin level measured in subjects for 1992 and published data from other studies considered in relation to existing goals and standards for the metabolic control of diabetes.
RESULTS: An ascertainment rate for people with diabetes of 1.36% was obtained. The rate of data capture for haemoglobin A1 was 75.7%, and the mean level for study samples was 10.5% at one laboratory and 10.0% at the other (similar values to those of comparable studies). These mean levels of haemoglobin A1 in representative populations of people with diabetes are poor or very poor according to published standards, including those of the British Diabetic Association. These findings are set in the context of the psychology of goal setting and performance in complex clinical situations.
CONCLUSION: Targets for clinical care that are set in the absence of normative data and local feasibility assessments should be treated with caution. Targets are more likely to enhance health care if target setters recognise the importance of psychological aspects of goal setting and motivation.