5176 Time In Range Preferred Over A1c And Fructosamine To Monitor Glycemic Control In Sickle Cell Disease

Abstract Disclosure: A. Patel: None. B. Simon: None. Introduction: In sickle cell disease, hemoglobin A1c is unreliable due to anemia, hemolysis, transfusions, and increased red blood cell turnover. In this population, plasma glucose should be used to make a diagnosis of diabetes, but there are no reliable long-term measures of glycemic control. Measures of serum protein glycation such as fructosamine are often used as markers of short-term control[1]. Continuous glucose monitoring (CGM) time in range (TIR) may offer another more reliable metric of control in this population2. Case: A 58-year-old male presented to the office for uncontrolled type 2 diabetes mellitus. His medical history included sickle cell anemia (Hb SS disease), hypertension, monoclonal gammopathy, and priapism. He was diagnosed with type 2 diabetes mellitus approximately one year prior based on a fructosamine level of 470 umol/L (0-285 umol/L) and elevated fasting glucose level of 128 mg/dL. He started metformin 500 mg daily. Three months later, repeat fructosamine was 401 umol/L, and metformin was increased. Months later, fructosamine levels remained elevated at 419 umol/L; metformin was increased to 2 grams daily and he was referred to endocrinology. The patient was given a CGM (Freestyle Libre 2 system, Abbott Diabetes Care) as an additional method to assess control. CGM showed an excellent 2-week TIR (70-180mg/ dL) of 98%. Repeat fructosamine after 2 weeks of CGM wear was elevated at 500 umol/L. It was hypothesized that the history of IgG kappa monoclonal gammopathy was falsely elevating his fructosamine level. A glycated albumin level was 13.5% (10.7-13.5%). The patient was advised to discontinue his metformin. Four months later, his glycated albumin remained in range, and a 2-week TIR was 100%. Discussion: This case demonstrates how sickle cell disease and monoclonal gammopathy affect laboratory values typically used to diagnose and monitor type 2 diabetes. Fructosamine, a measure of non-enzymatic glycation of serum proteins, is non-specific2. Increased protein from monoclonal gammopathy (giving more protein glycation sites) was the probable cause of the persistently elevated fructosamine, leading to overtreatment of what may not have been a true diagnosis of diabetes. This case also demonstrates the value of CGM, with glucose values and TIR indicating near normoglycemia. Diagnostic CGM may be a useful measure of glucose control in patients with hemoglobinopathies. References: 1. Danese E. et al. Advantages and pitfalls of fructosamine and glycated albumin in the diagnosis and treatment of diabetes. Journal of Diabetes Science and Technology. 2015;9(2):169–176. 2. Beck, RW. et al. The Fallacy of Average: How Using HbA1c Alone to Assess Glycemic Control Can Be Misleading. Diabetes Care 2017; 40: 994–999. Presentation: 6/1/2024