A1C Test Errors

Submitted by Thiruvelan on Mon, 10/17/2016
A1C Test Errors

What causes A1C error? A1C increases or decreases due to problems relating to RBC, hemoglobin, bilirubin, and supplement use.

Wise men learn from other men's mistakes; fools insist on learning from their own. ~ Albanian Proverb

9 Undesirable Factors Affecting HbA1C test

 Any variation in the RBC (or erythrocyte) or hemoglobin may cause hba1c errors. A1C can be increases or decreases by various factors; they are:

  1. Decrease or increase in erythrocyte (RBC) makes your A1C lower or increase, respectively.
  2. Hemoglobin Variants - Hemoglobin S-trait affects about 8% of African Americans. Hemoglobin C trait affects approximately 3% of African Americans. Hemoglobin E trait affects 10% to more than 50% of Southeast Asians in California. These Hb variants are all reported to affect some HbA1c assay methods. Elevated hemoglobin F has an association with thalassemia syndromes, also affects some assay methods.
  3. Hypertriglyceridemia interfered with some assay methods and increases result.
  4. High bilirubin interferes with some assay methods and increases result.
  5. Aspirin interfered with some assay methods and falsely increasing result.
  6. Chronic alcohol abuse produces a false high.
  7. Splenectomy is a surgical procedure (partial or complete removal of the spleen); this raises A1C.
  8. Chronic liver disease has false A1C low.
  9. Vitamin C & E ingestion interfere with some assay methods and decrease result.

A little doubt saves many a mistake. ~ Albanian Proverb

Causes of a decrease in erythrocyte that gives lower A1C result:

  1. Anemia, Thalassemia or hemolytic anemia, and liver disease,
  2. Hemorrhage or bleeding - heavy menstrual periods in women and stomach ulcers,
  3. Hemolysis (RBC destruction) - due to transfusion, blood vessel injury, or other causes,
  4. Erythropoietin deficiency - due to kidney diseases, Uremia (BUN more than 85 mg/dl), and Severe nephropathy.
  5. Bone marrow conditions - include leukemia, multiple myelomas (plasma cells cancer), and lymphoma (blood cancer).
  6. Medical conditions lead to low RBC count include cancer, rheumatoid arthritis, HIV/AIDS.
  7. Nutritional deficiencies, iron, copper, folate, and vitamin B6 & B12 can affect the result.
  8. Some medications, such as drugs used for chemotherapy, chloramphenicol, hydantoins, and quinidine.
  9. Overhydration
  10. Pregnancy

Causes of an increase in erythrocyte (that gives high A1C)

  1. Cigarette smoking
  2. Congenital heart disease
  3. Dehydration (due to severe diarrhea)
  4. Kidney tumor (renal cell carcinoma)
  5. Low blood oxygen level (hypoxia)
  6. Pulmonary fibrosis
  7. Polycythemia Vera
  8. Medication: Gentamicin, Methyldopa

Once you recognize the A1C interferences, then choosing an alternative form of test. These tests are glycated serum protein testing (fructosamine or glycated albumin). It helps assess glycemia better. Unfortunately, factors affecting the HbA1c accuracy cannot recognize clinically.

How often should you have an A1C test?

  • Pre-diabetes can check A1C once per year to track the progression of type 2 diabetes.
  • Type 2 diabetics should take the A1C test at least twice per year if your blood sugar is in a healthy range and stable.
  • Type 2 diabetes with high blood sugar and undergoing treatment modification should have an A1C test every three months until BS stabilizes.
  • Type 1 diabetes should check their A1C quarterly.

Because your A1C changes over months, checking it more often than quarterly is of limited or no use.

Can I use A1C for the diagnosis of pre-diabetes and diabetes?

  • Healthy non-diabetic has an A1C of less than 5.7%
  • Pre-diabetes (Increased chance to develop diabetes) A1C range is between 5.7 and 6.4 %.
  • An A1C level of 6.5 % or higher on two separate instances states you have diabetes.

Reference: A1C for Screening and Diagnosis of Type 2 Diabetes in Routine. Clinical Practice Diabetes Care 2010 Apr; 33(4): 817-819.

A1C test for diabetes diagnosis might lead to over or miss the diagnosis. Elders, black with an iron-deficient and genetic predisposition to high glycation are prone to over-diagnose.

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