ODP169 Challenges with use of HbA1C for Evaluation of Blood Glucose Control

BACKGROUND: Glycated hemoglobin (A1C) is widely used to diagnose diabetes mellitus and monitor glucose control. It represents a measurement of a proportion of glycated hemoglobin which reflects average glycemia over the lifespan of a red blood cell. Genetic factors that affect A1C values have been extensively studied and there is a growing knowledge of some variants that lead to abnormal fasting glucose-A1C ratio. Still, in some patients, delayed diagnosis or suboptimal treatment of diabetes mellitus remains an existing problem when glycated hemoglobin is underestimating blood glucose levels. CASE: 69-year-old man was seen in endocrine clinic following a hospital admission for newly diagnosed type 2 DM with hyperglycemic hyperosmolar state and a complicated urinary infection. Prior to admission the patient presented to primary care physician with symptoms of urinary infection and was found to have glucose >500mg/dL on point-of-care test and A1C of 9.5% without known history of diabetes mellitus. After a short hospital course the patient was discharged to home on low dose basal insulin and metformin. His morning glucose in the week after hospital stay was ranging between 140-182mg/dL. At the time of first visit in endocrinology he endorsed symptoms suggestive of peripheral neuropathy and had long standing polyuria, normal BMI and no other medical history or complaints. He was educated about the new diagnosis, diabetic diet, treatment and monitoring and no medication change was made at that time. On the next follow up he reported home glucose readings of 134-191mg/dL and repeated A1C was 5.1%. Urine test was remarkable for microalbuminuria and blood test showed low Hb of 8.7g/dL. Work up for anemia revealed alpha talassemia minor, hemoglobin SC disease and G6PD deficiency. During the following year regular clinic follow up visits were conducted, insulin was discontinued and the patient remained on metformin and empagliflozin over the next 4 years to date. When goal glucose control was achieved with fasting glucose of 90-130mg/dL A1C was 3.8% without any hypoglycemia. Hemoglobin at that time was 9.1g/dL. Over the next 4 years and to date his A1C was still checked 1-2 times a year and remained between 4-4.6%. On review of this patient's chart prior to hospital admission his HbA1C was 5.7% so diabetes mellitus was not suspected before the patient developed diabetic emergency that carries high mortality Discussion: There are known genetic and non-genetic factors that affect HbA1C value. It is very likely that this patient as well as many others have significant delay in diagnosis of diabetes mellitus if only HbA1C is used as screening test. A possibility of genetic variant that affects A1C values, especially in patients of African descent should always be considered when there is a discrepancy between fasting glucose and glycated hemoglobin value. Presentation: No date and time listed