HBA1C

Notes:

  1. RBCs have a life cycle of 8-12 weeks.
  2. HbA1C is formed by glycation (attachment of glucose) to Hb and reflects glucose concentration of the previous 2-3 months.
  3. HbA1C diagnostic of DM – 6.5% (48mmol/mol)
  4. goal of DM management – <7%

a.png

Factors that alter the HbA1C value:

  1. erythrocyte life span
    • increased lifespan – increases time RBC is exposed to glucose, increases HbA1C falsely, (ex. splenectomy)
    • decreased lifespan – HbA1C decreased (ex. hemolytic anemia)
  2. erythropoiesis
    • decreased erythropoiesis – increases mean age of RBC, increases HbA1C level (ex. iron deficiency anemia)
    • severe CKD decreases erythropoietin levels
  3. severe hypertriglyceridemia and chronic alcoholism
    • interferes with assay
  4. Hb variants – yields inaccurate results
  5. genetic factors or the “glycation gap”
    1. genes that affect RBC life span or glycation

ab.png

ALTERNATIVE TESTING METHODS

 

  1. glycated albumin and fructosamine (measures all glycated serum protein)
    1. half life of albumin is 14-21 days; all glycated serum protein tests reflect average blood glucose concentrations over the previous 2-3 weeks
    2. not affected by RBC disorders but by serum protein abnormalities (i.e. nephrotic syndrome)
  2. daily fingerstick
  3. continuous glucose monitor
  4. serum 1,5 anhydroglucitol (1,5-AG) test

 

CONVERSION A1C EST AVE BLOOD GLUCOSE:

The formula for converting A1C to an estimated average blood glucose level, according to the American Diabetes Association, is (28.7 x A1C) – 46.7 = estimated average glucose.

Capture

Conversion table (A1C to EAG)

 

References

O’Keeffe, Derek T., Spyridoula Maraka, and Robert A. Rizza. “Hba 1C In The Evaluation Of Diabetes Mellitus”. JAMA 315.6 (2016): 605. Web. 13 Feb. 2016.

Nhrmc.org,. N.p., 2016. Web. 13 Feb. 2016.  https://www.nhrmc.org/~/media/files/ diabetes-health-plan/class-materials/diabetes-overview-class/conversion-table-revised-12-30-14.pdf?la=en

 

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