Hemoglobin A1C

Aka: Hemoglobin A1C, Glycosylated Hemoglobin, HBA1C, HgbA1c

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II. Epidemiology

  1. Hemoglobin A1C may be important measure in non-diabetic
  2. Hemoglobin A1C associated mortality (contrast with <5)
    1. Relative Risk of Hemoglobin A1C 5.0 to 5.4
      1. All cause mortality: 1.41
      2. Cardiovascular mortality: 2.53
    2. Relative Risk of Hemoglobin A1C 5.4 to 6.9
      1. All cause mortality: 2.07
      2. Cardiovascular mortality: 2.46
    3. Relative Risk of Hemoglobin A1C 7.0 or higher
      1. All cause mortality: 2.64
      2. Cardiovascular mortality: 5.04
    4. References
      1. Khaw (2001) BMJ 322:15-8 [PubMed]

III. Background

  1. Glycosylated Hemoglobin is not equivalent to A1C
    1. Hemoglobin A1C is 70% total Glycosylated Hemoglobin

IV. Causes: Falsely lower Hemoglobin A1C

  1. Acute blood loss
  2. Chronic Liver Disease
  3. Splenomegaly
  4. Hemolytic Anemia
  5. HIV Antiretrovirals
  6. Pregnancy
  7. Vitamin E supplementation
  8. Vitamin C supplementation

V. Causes: Falsely higher Hemoglobin A1C

  1. Aplastic Anemia
  2. Hyperbilirubinemia
  3. Hypertriglyceridemia
  4. Iron Deficiency Anemia
  5. Renal Failure (Uremia)
  6. Splenectomy
  7. Chronic Alcohol Use Disorder
  8. Chronic Salicylate use
  9. Chronic Opioid use

VI. Causes: Falsely modified Hemoglobin A1C (variably affected)

  1. Hemoglobinopathy
  2. Malnutrition

VII. Interpretation: Approximating Serum Glucose from A1C

  1. Hemoglobin A1C of 6% represents mean Glucose of 130
  2. Each 1% increase in A1C, Glucose increases 30

VIII. Interpretation: Correlation to Mean Serum Glucose

  1. Hemoglobin A1C: 5.5% represents mean Glucose of 100
  2. Hemoglobin A1C: 7.0% represents mean Glucose of 150
  3. Hemoglobin A1C: 8.0% represents mean Glucose of 180
  4. Hemoglobin A1C: 9.0% represents mean Glucose of 220
  5. Hemoglobin A1C: 10.0% represents mean Glucose of 250
  6. Hemoglobin A1C: 11.5% represents mean Glucose of 300
  7. Hemoglobin A1C: 13.0% represents mean Glucose of 350

IX. Interpretation: Fasting vs post-prandial Hyperglycemia

  1. Hemoglobin A1C <7.3%:
    1. Postprandial Glucose: 30%
    2. Fasting Glucose: 70%
  2. Hemoglobin A1C 7.3-8.4%
    1. Postprandial Glucose: 50%
    2. Fasting Glucose: 50%
  3. Hemoglobin A1C 8.5-9.2%
    1. Postprandial Glucose: 55%
    2. Fasting Glucose: 45%
  4. Hemoglobin A1C 9.3-10.2%
    1. Postprandial Glucose: 60%
    2. Fasting Glucose: 40%
  5. Hemoglobin A1C >10.2%
    1. Postprandial Glucose: 70%
    2. Fasting Glucose: 30%
  6. References
    1. Monnler (2003) Diabetes Care 26:881-5 [PubMed]

X. Interpretation: Diagnosis of Diabetes Mellitus

  1. Hemoglobin A1C <5.2%: No Diabetes Mellitus
    1. Test Sensitivity: 100%
  2. Hemoglobin A1C >6.5%: Diabetes Mellitus
    1. Test Specificity: 100%

XI. References

  1. Malkani (2011) Am J Med 124(5): 395-401 +PMID:21531226 [PubMed]
  2. Pippitt (2016) Am Fam Physician 93(2): 103-9 [PubMed]

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