What is the Glycemic Achievement Gap (GAP) in hyperglycemia?

From the Guidelines

The Glycemic Achievement Gap (GAP) in hyperglycemia refers to the difference between the desired and actual blood glucose levels in patients with diabetes or hyperglycemia.

Key Points

• The desired blood glucose levels vary depending on the patient population, with a target range of 140–180 mg/dL (7.8–10.0 mmol/L) recommended for the majority of critically ill and noncritically ill patients 1.
• More stringent goals, such as <140 mg/dL (7.8 mmol/L), may be appropriate for selected patients, as long as this can be achieved without significant hypoglycemia 1.
• Higher glucose ranges, such as >250 mg/dL (13.9 mmol/L), may be acceptable in terminally ill patients with short life expectancy 1.

Glycemic Targets

• The American Diabetes Association recommends initiating insulin therapy for persistent hyperglycemia starting at a threshold of ≥180 mg/dL (10.0 mmol/L) 1.
• For noncritically ill patients with "new" hyperglycemia or known diabetes prior to admission, a target range of 100–180 mg/dL (5.6–10.0 mmol/L) is recommended 1.

Considerations

• Clinical judgment and ongoing assessment of clinical status, including changes in glucose measures, illness severity, nutritional status, and concomitant medications, should be incorporated into day-to-day decisions regarding insulin dosing 1.
• The use of continuous glucose monitoring (CGM) and automated insulin delivery systems can help improve glucose levels without increasing hypoglycemia 1.

From the Research

Definition of Glycemic Achievement Gap (GAP)

• The Glycemic Achievement Gap (GAP) is a measure of the difference between the actual blood glucose level and the expected blood glucose level based on the patient's HbA1c level 2, 3, 4, 5.
• It is calculated by subtracting the A1C-derived average glucose (ADAG) from the plasma glucose level at admission 2, 3, 4, 5.

Clinical Significance of Glycemic GAP

• A higher glycemic gap is associated with adverse outcomes in diabetic patients, including increased risk of mortality, multiorgan dysfunction syndrome, acute respiratory distress syndrome, shock, upper gastrointestinal bleed, acute kidney injury, and acute respiratory failure 2, 3, 4, 5.
• The glycemic gap can be used as a prognostic tool to predict adverse outcomes in critically ill patients with diabetes 3, 5.
• The calculation of the glycemic gap may increase the discriminative powers of established clinical scoring systems in diabetic patients presenting with acute myocardial infarction or community-acquired pneumonia 2, 4.

Calculation of Glycemic GAP

• The glycemic gap is calculated using the formula: Glycemic Gap = Plasma Glucose - A1C-derived Average Glucose (ADAG) 2, 3, 4, 5.
• The ADAG is calculated using the formula: ADAG = (28.7 x HbA1c) - 46.7 3, 5.

Studies on Glycemic GAP

• Several studies have investigated the association between glycemic gap and adverse outcomes in diabetic patients, including studies on community-acquired pneumonia 2, acute myocardial infarction 4, and critically ill patients 3, 5.
• These studies have consistently shown that a higher glycemic gap is associated with adverse outcomes in diabetic patients 2, 3, 4, 5.