Background: Hemoglobin A(1c) (HbA(1c)) has been used in controlled trials for the last 10 years but has never been evaluated in clinical practice as an effective parameter for clinical outcome. We investigated the trend for glycemic control over 11 years in one county of 350,000 citizens.
Methods: We studied 226,382 HbA(1c-DCCT-aligned) from 39,455 patients in whom routine monitoring for diabetes was initiated in 1993, 1996, or 2001. The trend in glycemic control was investigated in groups by probit plots, and in individual patients by target plots.
Results: From 1993 to 2001, the number of HbA(1c) measurements increased three-fold. The number of new monitoring series increased from 0.22% to 0.27% of the county population, and the number of patients monitored using HbA(1c) as a proxy for diabetes increased from 0.5% to 1.5%. A proportional reduction in high HbA(1c) concentrations of 5% was identified in the 1993 group, compared to 15% in the 1996 group, and 20% in the 2001 group. The percentage of patients with diabetic first HbA(1c) experiencing normalization increased from 8% to 30% for males and from 9% to 24% for females (1993-2001). The percentage of HbA(1c) concentrations that were not normalized decreased from 78% to 53% for males and from 83% to 59% for females (1993-2001). The median HbA(1c) at initiation of monitoring decreased from 8.7% in 1993 to 7.5% in 2001 (p < 10(-5)). The number of normal first HbA(1c) results in monitoring series increased from 7% to 17% for males and from 8% to 22% for females. Up to 10% of subjects developed diabetic concentrations during monitoring.
Conclusion: On average, patients with diabetic first HbA(1c) concentrations (> or =6.62%) showed an improvement in glycemic control from 5% in 1993 to 20% in 2001. High concentrations were easiest to reduce. In patients with originally diabetic HbA(1c) levels, 66% on average showed improved glycemic control in the 2001 series compared to 50% in the 1993 series. An average of 6% (1993) vs. 9% (2001) with originally normal HbA(1c) levels showed an upward trend inHbA(1c) levels. Median HbA(1c) at initiation of monitoring decreased from 8.7% in 1993 to 7.5% in 2001 (p < 10(-5)). The incidence of new cases was constant.