Abstract
BackgroundThe diagnosis of diabetes mellitus (DM) is based on either fasting plasma glucose levels or an oral glucose tolerance test (OGTT). Recently, an HbA1c value of ≥ 48 mmol/mol (6.5%) has been included as an additional test to diagnose DM. The purpose of this study was to validate HbA1c versus OGTT as a method to diagnose DM in vascular surgery patients.MethodsThe study population consisted of 345 patients admitted consecutively due to peripheral arterial disease. Sixty-seven patients were previously diagnosed with DM. Glucose levels of OGTT and HbA1c values were analyzed in 275 patients. The OGTT results were categorized into three groups according to the World Health Organization 1999 criteria: 1) DM defined as fasting plasma glucose (FPG) ≥ 7.0 mmol/L and/or two-hour value (2-h-value) ≥ 11.1 mmol/L; 2) intermediate hyperglycaemia, which consists of IGT (FPG < 7.0 mmol/L and a 2-h-value between 7.8 mmol/L and 11.1 mmol/L), and IFG (fasting glucose value between 6.1 mmol/L and 7.0 mmol/L with a normal 2-h-value); and 3) normal glucose metabolism defined as FPG < 6.1 mmol/L and a 2-h-value < 7.8 mmol/L.ResultsOf the 275 patients on whom OGTT was performed, 33 were diagnosed with DM, 90 with intermediate hyperglycaemia and 152 had normal glucose metabolism. An HbA1c value of ≥ 48 mmol/mol (6.5%) detected DM with a 45.5% sensitivity and a 90% specificity compared with the OGTT results. Combining the measurements of the HbA1c value with the fasting plasma glucose level (≥7.0 mmol/L) increased the sensitivity to 64%. The total prevalence of DM and intermediate hyperglycaemia was 85% based on HbA1c values and 45% based on the OGTT.ConclusionsCompared with the OGTT the HbA1c cut-off value of ≥ 48 mmol/mol (6.5%) had a 45.5% sensitivity to diagnose DM in patients with peripheral arterial disease. OGTT and HbA1c categorized different individuals with DM and intermediate hyperglycaemia. The total prevalence of pathologic glucose metabolism was substantially higher based on HbA1c values than based on OGTT. The high prevalence of DM and intermediate hyperglycaemia when using HbA1c in this study may reflect a high chronic glycaemic burden in patients with peripheral arterial disease. Further studies on vascular surgery patients are needed to identify which method, OGTT or HbA1c, is the better in predicting DM and future clinical development of vascular disease.Trial registrationREK vest 14109
Highlights
The diagnosis of diabetes mellitus (DM) is based on either fasting plasma glucose levels or an oral glucose tolerance test (OGTT)
An increase in retinopathy is seen in the intermediate hyperglycaemia range of HbA1c and the overall risk assessment for DM is seen as a continuum from low risk to established DM [8]
The OGTT results were categorized into three groups according to the World Health Organization (WHO) 1999 criteria: 1) DM defined as fasting plasma glucose (FPG) ≥ 7.0 mmol/l and/or twohour value (2-h-value) ≥ 11.1 mmol/l 2) intermediate hyperglycaemia, which consists of in women using WHO criteria (IGT) defined as FPG < 7.0 mmol/L and a 2-h-value between 7.8 mmol/L and 11.1 mmol/L, and impaired fasting glucose (IFG) defined as fasting glucose value between 6.1 mmol/L and 7.0 mmol/L with a normal 2-h -value and 3) normal glucose metabolism defined as FPG < 6.1 mmol/L and a 2-h-value < 7.8 mmol/L
Summary
The diagnosis of diabetes mellitus (DM) is based on either fasting plasma glucose levels or an oral glucose tolerance test (OGTT). An HbA1c value of ≥ 48 mmol/mol (6.5%) has been included as an additional test to diagnose DM. The diagnosis of diabetes mellitus (DM) has, until recently, been based on blood glucose levels, i.e. either fasting plasma glucose (FPG) ≥7.0 mmol/l or an oral glucose tolerance test (OGTT) result of ≥11.1 mmol/l [1]. The HbA1c value reflects the average blood glucose over a 2-3 month period and has traditionally been used to evaluate the treatment of established DM. It has been described as a predictor for DM and of micro- and macrovascular disease [2,3,4,5,6]. The International Expert Committee of Diabetes, American Diabetes Association and the World Health Organization (WHO) have included HbA1c value ≥ 48 mmol/mol (6.5%) as an additional method for diagnosing DM [8,9,10]
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