Diagnostic and Prognostic Value of Glycated Hemoglobin (HbA1c) in Patients with Diabetes Mellitus and Thalassemia

Abstract

Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia, which is caused by impaired insulin secretion, insulin action, or both. Four complications of DM have been identified – diabetes microangiopathy including nephropathy, retinopathy and polyneuropathy and diabetes macroangiopathy. DM is diagnosed on the basis of one of the following criteria: 1. Presence of typical symptoms – polyuria, polyphagia, polydipsia, weight loss and accidental plasma glucose value ≥ 11.1 mmol/l. 2. Fasting plasma glucose level ≥ 7.0 mmol/l. 3. Oral Glucose Tolerance Test (OGTT) – 2-hour blood glucose level ⩾ 11.1 mmol/l. 4. Test for glycated hemoglobin HbA1c⩾6.5%. Regular monitoring of blood glucose is crucial for good control of diabetes. Two are the most commonly available methods for glycemic monitoring – 1) home self-assessment; 2) HbA1c test. In this paper we discuss the diagnostic and prognostic value of HbA1c in comorbid patients with DM and diseases, where there are deviations in hemoglobin and erythrocyte values. In the scientific literature, single reports are available that give scarce guidance on how to manage these patients. It is mentioned that anemia should be treated individually, however no data could be found on what should be the standard behavior in such patients. According to the American Diabetes Association, only the blood glucose should be used when the relationship between HbA1c and glycemia is altered. Because of the diverse gene pool of the US population, different variants of hemoglobin may interfere with HbA1c measurements, although tests in the USA are standardized. Discrepancies between HbA1c and plasma glucose should suggest that testing for HbA1c may not be reliable for a particular patient. We present a clinical case of a comorbid patient with DM and thalassemia minor, whose glycemic control with glycated hemoglobin HbA1c is unreliable.