Why isn’t it enough to measure change in HbA1c when evaluating an intervention?

The HbA1c is a valuable measure of average blood glucose levels in the past 6 to 8 weeks, and a reliable indicator of future health as it is strongly associated with risk of diabetes-related complications. However, it does not provide information about the individual’s everyday hypos and hypers or their self-care activities, and it does not tell us anything about their knowledge of diabetes, their beliefs about diabetes, their self-management skills, their confidence, or how diabetes impacts on their emotional well-being or quality of life. Yet, all these variables are important outcomes to be considered when evaluating an intervention targeting diabetes self-care. The demands of diabetes self-care can be considerable. Therefore, one of the crucial determinants of a successful intervention and implementation is the behaviour itself. Furthermore optimal blood glucose levels do not necessarily equate to optimal quality of life or vice versa. For example, maintaining very tight blood glucose levels might result in an HbA1c within target range but the efforts to achieve that might impair the individual’s emotional well-being or quality of life. It may be possible to find other ways to maintain an optimal HbA1c or it might even be appropriate to relax those efforts for a while.