FP02-5 A1C An Inaccurate Measure of Glycemic Control in a Woman With Hereditary Spherocytosis (HS) Despite Normal Hemoglobin Levels

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP02-Obesity and Diabetes: Drugs & Interventions
Basic/Translational
Saturday, June 15, 2013: 11:00 AM-11:30 AM
Presentation Start Time: 11:20 AM
Room 303 (Moscone Center)

Poster Board SAT-758
Nora Alghothani*, Kathleen M Dungan and Prathima Pangulur
The Ohio State University, Columbus, OH
Background:  Two earlier cases have documented a discrepancy between A1C levels and glycemic control in patients with diabetes and HS. This however has not been reported for mild HS with normal hemoglobin despite a high incidence of diabetes in this hemolytic disorder.

Clinical Case:  A 22 year old Caucasian woman with type 1 diabetes diagnosed at age 11 was referred to Endocrinology for persistent hyperglycemia. Her regimen consisted of Lantus 16 units twice daily and Humalog 8 units with meals. Her initial A1C was 5.1% (n , 4.3 - 6.1 %) and routine chemistry and CBC revealed normal creatinine (0.67 mg/dL, n 0.60 - 1.10 mg/dL), hemoglobin (12.7 g/dL, n 11.1-15.5g/dL), hematocrit (35.7%, n 35-45%), MCV (85.5 fL, n 81-100 fL), MCHC (35.5 g/dL, n 32-36 g/dL), and RBC distribution (14.7, n 11.6-14.8). Exam was normal without hepatosplenomegaly. Given self-reported hyperglycemia, fructosamine, which measures the glycosylation of serum proteins rather than hemoglobin, was checked and was elevated (358 umol/L, n 200-285 umol/L). A peripheral smear was then obtained to assess for the presence of schistocytes or other RBC abnormalities that may falsely lower A1C, and found to be normal. Patient was eventually started on subcutaneous continuous insulin infusion. She had professional retrospective continuous glucose monitoring over a 6 day period that demonstrated marked hyperglycemic excursions, particularly in the evenings, with mean sensor glucose of 228 mg/dL +/- 102, and corresponding A1C of 5.4% and fructosamine of 365 umol/L. Throughout her 5 years of follow up, A1C ranged 4.0-5.6% and fructosamine 289-435 umol/L. She otherwise remained in overall good health with improved glycemic control. About 4 years after initial presentation, she reported a new diagnosis of spherocytosis in her mother, which prompted a work up for HS. A reticulocyte count was elevated at 5.4% (n 0.5 - 1.5 %) and an osmotic fragility test was supportive of HS with increased erythrocyte osmotic fragility due to spherocytosis. She was started on folic acid and recently became pregnant.

Conclusion:  This is the first case demonstrating a marked distortion of A1C in HS with normal hemoglobin. Given the relatively high frequency of mild HS, early testing should be considered in patients with an apparent discrepancy in A1C and meter readings, even in the absence of anemia. Alternate glycemic markers such as fructosamine are necessary to monitor chronic diabetic control in affected patients.

Nothing to Disclose: NA, KMD, PP

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