New Updated Hypoglycemia Classifications

A new report reviewing the impact of hypoglycemia on patients with diabetes will also provide guidance about how this new information should be incorporated into clinical practice….

Five members of the American Diabetes Association and five members of The Endocrine Society with expertise in different aspects of hypoglycemia were invited by the Chair, who is a member of both, to participate in a planning conference call and a 2-day meeting also attended by staff from both organizations.

The writing group considered data from recent clinical trials and other studies to update a prior workgroup report. Expert opinion was used to develop some conclusions.

How should hypoglycemia be defined?

The Workgroup first established a set of guiding principles regarding the ideal definition of hypoglycemia in individuals with diabetes. First, the optimal definition should be applicable to clinical decision-making by people with diabetes and their care providers as well as to studies of diabetes drugs, devices, or management strategies, although the standards for documenting and reporting hypoglycemia in studies need to be more stringent than those in the clinical setting. Second, the definition should be 1) free from reporting biases, 2) clinically important, 3) applicable to all persons with diabetes, 4) applicable to any time of day, 5) measurable by practical and widely available methods, and 6) reportable in a standardized fashion.

Given these parameters, the Workgroup’s overarching definition of hypoglycemia includes all episodes of an abnormally low plasma glucose concentration that expose the individual to potential harm. With regard to the latter issue, it is not only the nadir glucose concentration and the duration of hypoglycemia that may be inherently dangerous; frequent hypoglycemic events interfere with daily living and, even if asymptomatic, lead to defective glucose counterregulation and hypoglycemia unawareness. Since these episodes increase the risk of subsequent hypoglycemia substantially, all hypoglycemic events can harm the individual with diabetes in the short or long term. In addition to glucose counterregulatory systems that are triggered at an (arterialized venous) plasma glucose concentration of 65–70 mg/dl (3.6 –3.9mmol/l) in nondiabetic people, warning symptoms of hypoglycemia are
critical to permit interventions that also restore the plasma glucose concentration toward normal.

Thus, symptoms of a low plasma glucose, it can be argued, may be included in a definition of hypoglycemia. It is acknowledged that symptoms are idiosyncratic and nonspecific and may either not be recognized as such or be absent. Alternatively, it could be argued that hypoglycemia — literally low blood glucose — is by definition diagnosed by a low plasma glucose value. Thus, the question arises as to whether symptoms associated with hypoglycemia should ever replace a glucose value. Although it is appreciated that people with diabetes often know when they are hypoglycemic, there is also the very gray area that occurs when comorbid conditions or therapies produce symptoms similar to those that occur during hypoglycemia (e.g., palpitations, tremor, hunger, or sweating) or in patients with hypoglycemia unawareness.

Clearly, it is important for patients to measure their glucose levels when they think they are hypoglycemic. The reality, however, is that a plasma glucose level is not always obtained.

Finally, the question arises as to how a glucose level used to define hypoglycemia should be measured. Although a precise laboratory-based plasma glucose measurement would be ideal, monitor-based estimates (or those with a validated glucose sensor) are the only practical method. Albeit a function of mean glycemia and therefore a useful index of overall glycemic control and generally inversely related to the frequency of hypoglycemia, the HbA1c level is not an alternative to plasma glucose values.

Consensus was achieved by group discussion during conference calls and face-to-face meetings, as well as by iterative revisions of the written document.

The workgroup reconfirmed the previous definitions of hypoglycemia in diabetes, reviewed the implications of hypoglycemia on both short- and long-term outcomes, considered the implications of hypoglycemia on treatment outcomes, presented strategies to prevent hypoglycemia, and identified knowledge gaps that should be addressed by future research.

In addition, tools for patients to report hypoglycemia at each visit and for clinicians to document counseling were provided. See This Weeks Tool for Your Practice for a pdf you can print out of the new Hypoglycemia Classification.