Endocrine Abstracts

Glycosylated haemoglobin (HbA1c) is considered the Gold Standard parameter for evaluating long-term glycemic control in individuals with Diabetes Mellitus (DM). The presence of hemoglobin variants or others conditions that modify its glycosylation, can affect the veracity of its measurement. The detection of these hemoglobinopathies and his knowledge by the clinicians is very important for the correct diagnosis and follow-up. We present the case of a patient who presented a hemoglobinopathy that interferes with the determination of HbA1c by HPLC, one of the methods most used in laboratories. The case is about a man of 17 years old referred for evaluation by Endocrinology because in the context of a study of syncopal episodes and possible hypoglycaemia presents HbA1c of 6.5% with repeated blood fasting glucose between 70 and 75 mg/dl. A new HbA1c with a result of 7.0% and other exams were requested, which were normal: oral glucose tolerance test, negative autoantibodies (GAD, IA-2 and insulin), plasma C-peptide and insulinemia. Blood count parameters were also normal. He had no family history of DM to suspect Monogenic Diabetes. Levels of fructosamine (alternative marker for assessing glycemic control of the last 2–3 weeks, based on glycoproteins measurement) were requested, resulting in 240 μmol/l, which correlated with a calculated HbA1c of 5.6%. In addition to the incongruity between the HbA1c values and the rest of the study, an abnormal peak in the HbA1c chromatogram (HPLC assay) was observed. HbA1c was measured again by a different method (boronate affinity chromatography) resulting in a very different result (HbA1c 5.3%). Due to the suspicion of hemoglobinopathy that overestimates HbA1c, it was sent to the reference laboratory for molecular characterization. Finally, the patient presented hemoglobin J-Camagüey heterozygous (Arg>Gly; HBA1: c.424C>G). The mother also presented the same hemoglobinopathy in heterozygous.

Conclusions: Many patients may present simultaneously a hemoglobinopathy and DM. Some hemoglobinopathies, without clinical repercussion are detected incidentally during the measurement of HbA1c. It is important for clinicians to be aware of its existence, because some may falsify the results (underestimating or overestimating HbA1c, such as J-Camagüey). The use of alternative glycemic markers may be helpful in these cases.