Misleading Hemoglobin A1c Levels in a Patient With Paroxysmal Nocturnal Hemoglobinuria

Objectives: We report a case of a patient with diabetes mellitus and unexpectedly low hemoglobin A(1c) results associated with paroxysmal nocturnal hemoglobinuria (PNH). We review the impact of shortened RBC half-life on the interpretation of hemoglobin A(1c) levels. Methods: Patient history and laboratory test results were obtained from electronic medical records and analyzed. Results: The patient's hemoglobin A(1c) declined in parallel to worsening anemia after the diagnosis of PNH. However, elevated serum glucose (random), fructosamine, and glycated albumin suggest ongoing hyperglycemia. Together, these results argue that the decline in hemoglobin A(1c) was due to decreased RBC survival secondary to PNH. Conclusions: Hemoglobin A(1c) levels must be interpreted with caution in patients with hematologic diseases that change RBC survival. Serum fructosamine and glycated albumin measurements are alternative measures of time-averaged blood glucose control and may be useful in this subset of patients.