Hemoglobin (Hb) A1c

CPT: 83036
Updated on 12/1/2017
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Test Details

Synonyms

  • Glycated Hemoglobin
  • Hgb A1c

Use

Hemoglobin A1c values are used to assess glucose control in diabetes, and in 2010 the American Diabetes Associations affirmed the decision of an international expert committee recommendation to use the A1c test to diagnose diabetes with a threshold ≥6.5%. Point-of-care A1c assays are not sufficiently accurate at this time to use for diagnostic purposes.

Limitations

Any cause of shortened erythrocyte survival will reduce exposure of erythrocytes to glucose with a consequent decrease in Hb A1c (%). Causes of shortened erythrocyte lifetime might be hemolytic anemia or other hemolytic diseases, homozygous sickle cell trait, pregnancy, or recent significant or chronic blood loss. Glycated Hb F (fetal hemoglobin) is not detected as it does not contain the glycated β chain that characterizes Hb A1c. Specimens containing high amounts of Hb F (>10%) may result in lower than expected Hb A1c.

Methodology

Roche Tina Quant

Reference Interval

• Hemoglobin (Hb) A1c: 4.8% to 5.6%

• Prediabetes: 5.7% to 6.4%

• Diabetes: ≥6.5%

• Glycemic control for adults with diabetes: <7.0%

(DCCT/NGSP)

2010 American Diabetes Association's Summary of Glycemic Recommendations for Adults with Diabetes: Hemoglobin A1c <7.0%.

For selected individual patients, providers might reasonably suggest even lower A1c goals than the general goal of <7%, if this can be achieved without significant hypoglycemia or other adverse effects of treatment. Such patients might include those with short duration of diabetes, long life expectancy, and no significant CVD. Conversely, less-stringent A1c goals than the general goal of <7% may be appropriate for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, and extensive comorbid conditions and those with longstanding diabetes in whom the general goal is difficult to attain.

Additional Information

Factors such as duration of diabetes, adherence to therapy, and age of patient should also be considered in assessing the degree of blood glucose control.

Specimen Requirements

Specimen

Whole blood

Volume

4 mL

Minimum Volume

Pediatric EDTA whole blood tubes may be used. Please place original labeled capillary tube in a labeled transport tube for shipment to the laboratory.

Pediatric EDTA whole blood tubes may be used. Please place the entire collection in a transport tube for shipment to the laboratory.

Pediatric EDTA whole blood tubes may be used. Please place original labeled capillary tube in a labeled transport tube for shipment to the laboratory.

Container

Lavender-top (EDTA) tube, green-top (lithium heparin) tube, or gray-top (sodium fluoride) tube

Collection

The usual precautions in the collection of venipuncture samples should be observed. The sample must be free of clots. Samples with any hematocrit disorders can lead to erroneous results. Send the entire tube to the laboratory.

Storage Instructions

Maintain specimen at room temperature.

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Clotted specimen; gross hemolysis

Clinical Information

References

American Diabetes Association. Summary of revisions for the 2010 Clinical Practice Recommendations. Diabetes Care. 2010 Jan; 33(Suppl 1):S3. 20042773
Bergstrom RW, Kelley JR, Ward WK. Fetal hemoglobin alters hemoglobin A1c measurements. Ann Intern Med. 1991 Oct 15; 115(8):656. 1716431
Fairbanks VF, Zimmerman BR. Measurement of glycosylated hemoglobin by affinity chromatography. Mayo Clin Proc. 1983 Nov; 58(11):770-773. 6632974
Holt GS, Wofford JL, Vélez R. Hemoglobinopathies affect hemoglobin A1c measurement. Ann Intern Med. 1991 Jul 1; 115(1):68-69. 1760005
Krauss JS, Khankhanian NK. HPLC determination of hemoglobin A1c in the presence of the fast hemoglobin I-Philadelphia. Clin Chem. 1989 Mar; 35(3):494-495. 2920422

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
001453 Hemoglobin A1c 4548-4 001481 Hemoglobin A1c % 4548-4
Reflex Table for Hemoglobin A1c
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 001482 Please Note: 001482 Please Note: N/A

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