Glycosylated hemoglobin A

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Glycosylated hemoglobin A, also referred to by it medically most important component Hb A1c, is blood test used to monitor the treatment of diabetes mellitus type 1 and diabetes mellitus type 2. Glycosylated hemoglobin A are "minor hemoglobin components of human erythrocytes designated A1a, A1b, and A1c. Hemoglobin A1c is most important since its sugar moiety is glucose covalently bound to the terminal amino acid of the beta chain. Since normal glycohemoglobin concentrations exclude marked blood glucose fluctuations over the preceding three to four weeks, the concentration of glycosylated hemoglobin A is a more reliable index of the blood sugar average over a long period of time."[1]

The following table helps convert Hb A1c values to average daily blood glucose levels.[2]

  • 5% = 97 mg/dL
  • 6% = 126 mg/dL (6.99 mmol/L)
  • 7% = 154 mg/dL (8.54 mmol/L)
  • 8% = 183 mg/dL (10.16 mmol/L)
  • 9% = 212 mg/dL (11.77 mmol/L)
  • 10% = 240 mg/dL
  • 11% = 269 mg/dL
  • 12% = 298 mg/dL

For each 1% change in HbA1c approximates a 30 mg/dL (2 mmol/L) change in the average daily glucose.[2]

Other studies have different values[3][4] and older studies obtained different values.[5]

There is approximately 1 mmol/L between the fasting and postprandial glucose levels in treated diabetics.[6] This difference may be as high as 5 mmol/L difference in untreated diabetics (in the UGDP trial).[7]

Elevated hemoglobin A1c independently predicts outcome, even among patients without diabetes.[8]

References

  1. Anonymous (2015), Glycosylated hemoglobin A (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. 2.0 2.1 Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ (August 2008). "Translating the A1C assay into estimated average glucose values". Diabetes Care 31 (8): 1473–8. DOI:10.2337/dc08-0545. PMID 18540046. Research Blogging.
  3. Ramachandran A, Riddle MC, Kabali C, Gerstein HC, on behalf of the ORIGIN Investigators (2012). "Relationship Between A1C and Fasting Plasma Glucose in Dysglycemia or Type 2 Diabetes: An analysis of baseline data from the ORIGIN trial.". Diabetes Care 35 (4): 749-753. DOI:10.2337/dc11-1918. PMID 22323416. PMC PMC3308289. Research Blogging.
  4. Rohlfing CL, Wiedmeyer HM, Little RR, England JD, Tennill A, Goldstein DE (2002). "Defining the relationship between plasma glucose and HbA(1c): analysis of glucose profiles and HbA(1c) in the Diabetes Control and Complications Trial.". Diabetes Care 25 (2): 275-8. PMID 11815495[e]
  5. Koenig RJ, Peterson CM, Jones RL, Saudek C, Lehrman M, Cerami A (1976). "Correlation of glucose regulation and hemoglobin AIc in diabetes mellitus.". N Engl J Med 295 (8): 417-20. PMID 934240.
  6. Pupillo M, De Berardis G, Antenucci D, Minnucci A, Nicolucci A (2008). "Glycated haemoglobin or mean blood glucose as indicators of metabolic control in Type 2 diabetes?". Diabetes Res Clin Pract 80 (3): e1-3. DOI:10.1016/j.diabres.2008.01.001. PMID 18258329. Research Blogging.
  7. Feinglos MN, Bethel MA (1999). "Therapy of type 2 diabetes, cardiovascular death, and the UGDP.". Am Heart J 138 (5 Pt 1): S346-52. DOI:10.1016/S0002-8703(99)70034-7. PMID 10539796. Research Blogging.
  8. NEJM 2010 Glycated Hemoglobin, Diabetes, and Cardiovascular Risk in Nondiabetic Adults