Problems in assessing diabetes control in an ambulatory setting

Problems in using medical records to assess outcomes of diabetes care have not been well defined. We reviewed the medical records of 288 patients with diabetes receiving ambulatory care over a 2-year period. We determined the availability of different tests of glycemic control and described site performance as the percentage of patients with a blood glucose exceeding either 180 or 240 mg/dl. Glycosylated hemoglobin determinations were performed in only 26.7% of patients. A blood glucose was available in 208 patients (72.2%) during a 6-month outcome period. For almost 50% of the sample, the glucose was greater than 180 mg/dl, whereas in 20% it exceeded 240 mg/dl. Judgments of whether sites differed in performance depended on how control was defined. Using a single glucose determination and a threshold of 180 mg/dl, similar fractions of patients were poorly controlled at each site (51.2 versus 45.0 versus 47.0%) (P = 0.75). At 240 mg/dl, although, one site performed much worse than the other two (14.6 versus 16.7 versus 31.8%) (P = 0.02). These results highlight difficulties in defining the outcome measure when using medical records to evaluate quality of care