ARE EUROPEAN STANDARD-DEVIATION TARGETS FOR HEMOGLOBIN A(1C) TOO STRICT

The Diabetes Control and Complications Trial (DCCT) has provided objec tive evidence for desirable glycaemic control in Type 1 patients and d efines the benefits of good glycaemic control in terms of haemoglobin A(1c) (HbA(1c)) values. However, HbA(1c) assays vary, leading to sugge stions that glycaemic control be classified according to numbers of st andard deviations (SD) from a local non-diabetic population mean. We h ave classified the glycaemic control of 339 UK Type 1 diabetic patient s (182 male, 157 female, median age 36 (range 15-74) years) using the DCCT to set HbA(1c) targets and compared this with the SD method. Usin g age matched controls (mean HbA(1c) 4.02 %, SD 0.28 %, n=106), SD gui delines classified 1 % of patients into good (HbA(1c) <3SD from refere nce mean), 4% into borderline (3-5SD) and 95 % into poor (>5SD) glycae mic control. When calibrating the same instrument to the DCCT analyser (r= 0.996), 37 % of patients had HbA(1c) results lower than the 7% me dian value found in the intensively treated DCCT group, while only 12 % of patients had values greater than the 9 % conventionally treated m edian HbA(1c). DCCT subjects with HbA(1c) values of less than 8 % belo nged predominantly to the intensively treated group. In this study, 71 % of patients fell into this category. Thus, guidelines based on numb ers of SD away from a non-diabetic mean may overestimate the glycaemic control required to reduce microvascular complications in Type 1 pati ents. Standardizing to DCCT targets is more appropriate. (C) 1998 John Wiley & Sons, Ltd.