Lab Test

Hemoglobin A1C

Hgb A1c, glycated hemoglobin, HA1C

Test Codes

Antrim #17141, EPIC: LAB5858, SOFT: A1C

Department

Special Chemistry

Specimen Collection Criteria

Collect: One Lavender-top EDTA tube or one Lavender-top EDTA Microtainer®. (Minimum Whole Blood: 1.0 mL)

Physician Office/Draw Specimen Preparation

Store whole blood refrigerated (2-8°C or 36-46°F) prior to transport. (Minimum Whole Blood: 1.0 mL)

Preparation for Courier Transport

Transport: Whole blood, refrigerated (2-8°C or 36-46°F). (Minimum Whole Blood: 1.0 mL)

Rejection Criteria

  • Frozen specimens.
  • Moderate to grossly hemolyzed specimens.
  • Specimens not collected and processed as indicated.

In-Lab Processing

Store whole blood refrigerated (2-8°C or 36-46°F). (Minimum Whole Blood: 1.0 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Special Testing Laboratory
Dearborn Chemistry Laboratory

Performed

Monday – Friday, 24 hours a day; Saturday and Sunday (day shift only).
Results are available in 3-5 business days.

Reference Range

4.0-5.6 % Hb A1c

 4.0-5.6% HbA1c   Non-diabetic
 5.7-6.4% HbA1c  Pre-diabetic
 Greater than or equal to 6.5% HbA1c  Diabetic

Test Methodology

Royal Oak: High Performance Liquid Chromatography (HPLC).

Interpretation

Hemoglobin A1c values of 5.7-6.4 percent indicate an increased risk for developing diabetes mellitus. Hemoglobin A1c values greater than or equal to 6.5 percent are diagnostic of diabetes mellitus. In the absence of unequivocal hyperglycemia, results should be confirmed by repeat testing or fasting glucose measurement. Fasting blood glucose rather than hemoglobin A1c should be used to diagnose acute onset of type I diabetes mellitus.

Limitations and Interfering Substances:

Samples from patients with hemolytic anemias will exhibit decreased A1C values due to the shortened RBC life span.

Samples from patients known to have high alcohol consumption will interfere with the accurate analysis of Hb A1c.

Samples from patients with polycythemia iron deficiency or post-splenectomy may exhibit increased A1c values due to somewhat longer RBC life span.

In the unusual variant forms (SS, CC, SC), no HbA is present, and therefore no Hb A1c will be detected.

Clinical Utility

Hemoglobin A1c provides an index of the mean blood glucose concentration over the preceding 100-120 days. The level of Hb A1c is proportional to both the average glucose concentration and life span of the protein (hemoglobin) in the circulation or tissue. If a patient is known to have no hemoglobin A or acute or chronic hemolysis, Fructosamine (glycated plasma proteins) is useful to assess glycemic control.

CPT Codes

83036
LOINC: 4548-4

Contacts

Last Updated

1/11/2023

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