Endocrine Abstracts

Introduction: Diagnosis of Gestational Diabetes Mellitus (GDM) is with 75-g 2-hour Oral Glucose Tolerance Test (OGTT) at presentation and at 24 to 28 weeks when the first OGTT is normal. Although HbA1C is not recommended as a diagnostic test for GDM, this was used instead of OGTT during the Covid pandemic in the United Kingdom. Hemoglobin Wayne (Hb Wayne) is a rare variant of hemoglobin which may produce falsely high HbA1C level in some assays. We report a patient who was a carrier for Hb Wayne who presented with high HbA1C in pregnancy although her fructosamine and capillary blood glucose levels were in reference range.

Case report: A 30-year-old non-diabetic primigravida with family history of Type 2 diabetes and BMI of 24 kg/m² was screened for Gestational Diabetes Mellitus (GDM) at 14 weeks gestation using HbA1C instead of OGTT. Her HbA1c level at presentation was 89 mmol/mol (less than 42), although her capillary blood glucose levels were within euglycemic ranges, and fructosamine level was 257 umol/l (less than 330). Her Glutamate Decarboxylase and Islet autoantibodies were not raised. The fetal growth scans were within satisfactory parameters throughout pregnancy. She remained on diet and lifestyle with home monitoring of capillary blood glucose levels until the third trimester when she required treatment with metformin. She had elective Caesarean session at 39 weeks for personal preference, delivering a healthy baby (birth weight of 3.025 kg). In the postnatal period, her capillary blood glucose levels remained within euglycemic ranges after discontinuing Metformin. Her HbA1C remained high at 86mmol/mol with fructosamine level of 257 umol/l without treatment. She was found to be a carrier of Hb Wayne on haemoglobinopathy screening. This alpha chain variant heterozygous state is likely to have caused the falsely high HbA1C.

Conclusion: We report falsely high HbA1C in early pregnancy from Hb Wayne which may lead to overdiagnosis if used to screen for GDM instead of OGTT. Strategies to overcome this may include hemoglobinopathy screening and fructosamine level when HbA1C is high despite euglycemia on capillary blood glucose monitoring.