Evaluation of the usefulness of HbA1c measurement for diagnosing diabetes in a selected sample of the Polish population

Abstract

Introduction. Since January 2010, the American Diabe­tes Association has been recommending, apart from hitherto applied methods, the use of glycated haemo­globin concentration as one of the diagnostic criteria for diabetes, with a limit value HbA_1c ≥ 6.5%. The aim of the study was to evaluate the usefulness of HbA_1c measurement for diagnosing diabetes in a selected sample of the Polish population, and to attempt to determine a cut-off point for HbA_1c concentration de­fining diagnosis of diabetes, based on the examination of patients with risk factors of type 2 diabetes.

Material and method. Examinated 219 individuals (in this 142 women) in age 40–85 years, BMI 20–50 kg/m², with one of the risk factors for diabetes, sine previously diagnosed diabetes. All participants underwent the oral glucose tolerance test (75 g glucose); blood sam­ples were taken to determine HbA_1c levels by means of A_1cNow+ (Bayer). In addition, in 85 randomly selected individuals, HbA_1c concentration was concomitantly determined by means of high-performance liquid chromatography (HPLC).

Results. Diabetes was diagnosed in 22 individuals on the basis of the following criteria: fasting glyca­emia ≥ 126 mg/dl or glycaemia ≥ 200 mg/dl in 120^th minute of OGTT test. It was demonstrated that at the cut-point HbA_1c ≥ 5.7% the highest sum of sensiti­vity and specificity was achieved (sensitivity 77.3%, specificity 55.8%). For higher HbA_1c values, sensitivity was gradually decreasing, whereas specificity was increasing (e.g. for HbA_1c ≥ 6.1% sensitivity decreased to 36.4%, whereas specificity increased to 86.3%; for HbA_1c ≥ 6.6% sensitivity and specificity values were 13.6% and 95,9%, respectively).

Conclusion. A large range of values for sensitivity and specificity indicates a low usefulness of HbA_1c determination for diagnosing diabetes. The achieved “cut-off point” for obtaining the highest sensitivity and specificity is below the reference values, which is an additional argument against introduction of HbA_1c determination in diabetes diagnostics.