Continuous and flash glucose monitoring have revealed weaknesses of HbA1c as standard measure of glycemic control and introduced new indices for assessing glycemia. Glycemic variability (GV) is a measure of glycemic instability that can be mathematically defined as %CV. GV relates to both hyper/hypoglycemia and is a candidate for predicting diabetes specific outcomes. Our aim was to determine the correlation of CGM-derived glycemic parameters to the gold standard; HbA1c.
22 participants (HbA1c=7.1±1.3%,) with type 1 (n=11; %CV=42.3±6.9) and type 2 (n=11, %CV=35.4±6.7) diabetes, treated by basal bolus MDI were equipped with blinded CGM. CGM data were analyzed to determine glycemic control parameters. Correlation was assessed by Pearson correlation. Difference in glycemic variability between groups with HbA1c above or below 7%, was compared by paired sample t-test. Results were reported as mean±SD.
Glycemic variability (%CV) and time in hyper/hypoglycemia significantly correlated to HbA1c (Table 1). Patients with higher HbA1c experienced significantly higher %CV (Table 2).
| HbA1c | |||
| CGM-derived glycemic parameters | Pearson correlation coefficient | Strength of correlation | P-value |
| time in hyperglycemia | 0.452 | moderate | 0.035 |
| time in range | -0.191 | weak | 0.394 |
| time in hypoglycemia | -0.432 | moderate | 0.044 |
| time in grade II hypoglycemia | -0.540 | strong | 0.010 |
| % CV | 0.428 | moderate | 0.047 |
Table 1.
| HbA1c | %CV | P-value |
| below 7.0% | 38.9±9.5 | 0.007 |
| above 7.0% | 55.7±15.5 |
Table 2.
Assessment of glycemia should go beyond HbA1c, however HbA1c is widely used as a predictor of diabetes complications. We found a positive association of GV with HbA1c, which adds to the pool of indirect evidence on GV impact on diabetic complications.