title: Misleading hemoglobin A1c levels in a patient with paroxysmal nocturnal hemoglobinuria.
abstract: OBJECTIVE
  We report a case of a patient with diabetes mellitus and unexpectedly low hemoglobin A1c results associated with paroxysmal nocturnal hemoglobinuria (PNH). We review the impact of shortened RBC half-life on the interpretation of hemoglobin A1c levels.
  
  
  METHODS
  Patient history and laboratory test results were obtained from electronic medical records and analyzed.
  
  
  RESULTS
  The patient's hemoglobin A1c 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 A1c was due to decreased RBC survival secondary to PNH.
  
  
  CONCLUSIONS
  Hemoglobin A1c 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.
authors.affiliation: From the Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA, and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Xia
authors.affiliation: Department of Adult Medicine, South Cove Community Health Center, Boston, MA.
authors.forename: Randall
authors.initials: R
authors.lastname: McShine
authors.affiliation: From the Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA, and ahberg@bidmc.harvard.edu.
authors.forename: Anders H
authors.initials: AH
authors.lastname: Berg
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis; D003951:Diagnostic Errors; D019270:Fructosamine / Q000097:blood; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood* / Q000175:diagnosis*; D006801:Humans; D008297:Male
chemical_list: D001786:Blood Glucose; D019270:Fructosamine; D006442:Glycated Hemoglobin
keywords: Anemia; Diabetes; Hemoglobin A1c; Paroxysmal nocturnal hemoglobinuria; RBC half-life; RBC survival