Abstract 495

Increasing Frequency of Diabetes Clinic Visits is Associated with Improving Hemoglobin A1c

Background: Patients with type 1 diabetes are commonly seen every 3 to 4 months for disease education, review of blood sugars, and for measurement of hemoglobin A1c. We examine the relationship of spacing and change in hemoglobin A1c between visits.

Methods: Retrospective study with patients seen in a large hospital based pediatric diabetes clinic between 1995 and 1998. Inclusion criteria were all encounters for which a hemoglobin A1c was measured in the hospital laboratory within one day of the encounter. Patients seen only once were excluded. The change in hemoglobin A1c between pairs of consecutive encounters was plotted against the number of days between those encounters. A linear model was fit using the least-squares method, and the slope was compared for significance against zero slope, using a T statistic. Pairs of encounters spaced more than 1 year apart were excluded.

Results: Records were reviewed from 517 patients seen in 2536 consecutive pairs of encounters. Average spacing between visits was 114 days, with a standard deviation of 48 days. The regression line was y = 0.0035 x - 0.28, where x was the number of days between visits and y was the change in percent hemoglobin A1c between visits. With this model, no change in hemoglobin A1c was seen when visit spacing was 80.5 days; below this, hemoglobin A1c was decreased at the second visit and above this, hemoglobin A1c was increased at the second visit. The regression line had a slope statistically significantly different from zero (p < 0.001).

Conclusion: In our setting, decreasing the interval between diabetes clinic encounters is associated with decreasing hemoglobin A1c. Using this model, we find that follow up visits spaced more than 80 days apart are most likely to show an increase in hemoglobin A1c. Future prospective study and characterization of specific encounter factors are indicated.