ESPE Abstracts

Introduction: The glycated hemoglobin (HbA1c) corresponds to the fraction of Hb exposed to non-enzymatic glycation of the N-terminal part of the beta chain of Hb A, in case of elevation of blood sugar. Any change in erythropoiesis and/or lifetime of red blood cells will affect the reliability of HbA1c levels.

Case presentation: 12-year-old girl followed for growth homone deficiency, under growth hormone, in whom the annual assessment finds a high level of glycated hemoglogine, confirmed on several samples. There were no symptoms of diabetes, the capillary and venous glycemia were normal. An electrophoresis of hemoglobin was made finding a variant of hemoglobin: Hemoglobin D responsible for an abnormality of glycation of haemoglobin. Fructosamine assay was normal in our patient, and family investigation confirmed hemoglobinopathy.

Discussion and Conclusion: Any change in erythropoiesis and/or lifetime of red blood cells will affect the reliability of HbA1c levels. The presence of reticulocytes, in case of hemolysis, acute anemia or chronic hepatopathy but also treatment with iron, EPO or vitamin B12, or a recent transfusion may underestimate HbA1c. Conversely, the lengthening of the lifetime of red blood cells (advanced age, alcoholism, splenectomy, iron deficiency, folates or vit. B12) artificially increases HbA1c. Drugs that can induce hemolysis can cause a decrease in HbA1c: dapsone, interferon, ribavirin, antiretroviral. Structural changes in Hb may also distort the HbA1c assay. An abnormally high proportion of Hb F (thalassaemia) or D generally increases the HbA1c level while the presence of Hb S (sickle cell disease) or Hb C will underestimate its value. These hemoglobinopathies are now more easily detected thanks to the generalization of the dosage by HPLC. Chronic renal failure is responsible for an overestimation of HbA1c by accumulation of carbamylated Hb that can interfere with the dosing method. The HbA1c assay method may be in default in other situations: decreasing in case of hypertriglyceridemia; increasing in case of hyperbilirubinemia. It is important to combine the determination of glycated hemoglobin with the measurement of blood sugar, including self-monitoring glycemia in patients at risk. to avoid potentially serious errors in patient management. The dosage of fructosamine, measuring all extra-cellular glycated proteins and reflecting the average glycemic of the past 14-21 days may be useful, but is not used in common practice