Hemoglobin A1c, Blood
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Evaluating the long-term control of blood glucose concentrations in diabetic patients
Ion-Exchange Chromatography Quantitative
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Hemoglobin A1c, B
Glyco HGB (Glycosylated Hemoglobin)
Hemoglobin A1C, B
Glyco HGB (Glycosylated Hemoglobin)
Hemoglobin A1C, B
Specimen Type Describes the specimen type needed for testing
Whole Blood EDTA
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions: Send specimen in original tube.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Whole Blood EDTA||Refrigerated (preferred)||7 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Diabetes mellitus is a chronic disorder associated with disturbances in carbohydrate, fat, and protein metabolism characterized by hyperglycemia. It is one of the most prevalent diseases, affecting approximately 24 million individuals in the United States. Long-term treatment of the disease emphasizes control of blood glucose levels to prevent the acute complications of ketosis and hyperglycemia. In addition, long-term complications such as retinopathy, neuropathy, nephropathy, and cardiovascular disease can be minimized if blood glucose levels are effectively controlled.
Hemoglobin A1c (HbA1c) is a result of the nonenzymatic attachment of a hexose molecule to the N-terminal amino acid of the hemoglobin molecule. The attachment of the hexose molecule occurs continually over the entire life span of the erythrocyte and is dependent on blood glucose concentration and the duration of exposure of the erythrocyte to blood glucose. Therefore, the HbA1c level reflects the mean glucose concentration over the previous period (approximately 8-12 weeks, depending on the individual) and provides a much better indication of long-term glycemic control than blood and urinary glucose determinations. Diabetic patients with very high blood concentrations of glucose have from 2 to 3 times more HbA1c than normal individuals.
Diagnosis of diabetes includes 1 of the following:
-Fasting plasma glucose > or =126 mg/dL
-Symptoms of hyperglycemia and casual plasma glucose >or =200 mg/dL
-Two-hour glucose > or=200 mg/dL during oral glucose tolerance test unless there is unequivocal hyperglycemia, confirmatory testing should be repeated on a different day
In addition, recent recommendations from the American Diabetes Association (ADA) include the use of HbA1c to diagnose diabetes, using a cutpoint of 6.5%.(1) The cutpoint was based upon sensitivity and specificity data from several studies. Advantages to using HbA1c for diagnosis include:
-HbA1c provides an assessment of chronic hyperglycemia
-Assay standardization efforts from the National Glycohemoglobin Standardization Program have been largely successful and the accuracy of HbA1c is closely monitored by manufacturers and laboratories
-No fasting is necessary
-Intraindividual variability is very low (critical value of <2%)
-A single test could be used for both diagnosing and monitoring diabetes
When using HbA1c to diagnose diabetes, an elevated HbA1c should be confirmed with a repeat measurement, except in those individuals who are symptomatic and also have an increased plasma glucose >200 mg/dL. Patients who have an HbA1c > or =6.0 but < or =6.5% are considered at risk for developing diabetes in the future. (The terms pre-diabetes, impaired fasting glucose, and impaired glucose tolerance will eventually be phased out by the ADA to eliminate confusion.)
The ADA recommends measurement of HbA1c (typically 3-4 times per year for type 1 and poorly controlled type 2 diabetic patients, and 2 times per year for well-controlled type 2 diabetic patients) to determine whether a patient's metabolic control has remained continuously within the target range.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
> or =18 years: 4.0-6.0%
Reference values have not been established for patients that are <18 years of age.
Diagnosing diabetes American Diabetes Association (ADA)
-Hemoglobin A1c (HbA1c) >6.5%
Therapeutic goals for glycemic control (ADA)
- Goal of therapy: <7.0% HbA1c
- Action suggested: >8.0% HbA1c
- Toddlers and preschoolers: <8.5 % (but >7.5%)
- School age (6–12 years): <8%
- Adolescents and young adults (13–19 years): <7.5%
The 2009 ADA recommendations for clinical practice suggest maintaining a HbA1c value closer to normal yields improved microvascular outcomes for diabetics.(2) Target goals of <7% may be beneficial in patients such as those with short duration of diabetes, long life expectancy, and no significant cardiovascular disease. However, in patients with significant complications of diabetes, limited life expectancy, or extensive comorbid conditions, targeting a <7% goal may not be appropriate.
Since the HbA1c assay reflects long-term fluctuations in blood glucose concentration, a diabetic patient who has in recent weeks come under good control may still have a high concentration of HbA1c. The converse is true for a diabetic previously under good control who is now poorly controlled.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Most common hemoglobin (Hb) variants (HbF <15%, heterozygous HbC, heterozygous HbS) do not interfere with this HPLC method. Other variants of Hb may show interference with this method. The known variants that fall into this category are HbE, HbD, Hb Fukuoka, Hb Philadelphia, and Hb Raleigh.
If the specimen cannot be analyzed using HPLC due to a hemoglobinopathy or other interference, a second-tier test will be performed on the BIO-RAD in2it analyzer-a point-of-care NGSP-certified method utilizing boronate-affinity chromatography, which is least affected by Hb variants. Most specimens from patients with hemoglobinopathies can be accurately monitored with the boronate-affinity method.
In patients with rare homozygous forms of abnormal Hb (eg, CC, SS, EE, SC), there is no HbA present and thus no hemoglobin A1c (HbA1c) value can be quantitated using this method. In these patients, the RBC lifespan is often variable and although an HbA1c could be reported using a boronate-affinity method, it is likely not providing a true measurement of the patient's glycemic control and could lead to misinterpretation. In such situations, fructosamine should be used as an alternate measurement of glycemia and is recommended for monitoring these patients. Fructosamine is a stable ketoamine that represents intermediate-term glycemic control (2-3 weeks). See FRUCT Fructosamine, Serum.
In cases of hemolytic anemia, the lifetime of erythrocytes is shortened and will result in decreased glycated hemoglobin results. This effect will depend upon the severity of the anemia. Specimens from patients with polycythemia or post-splenectomy may exhibit increased glycated hemoglobin values due to a somewhat longer lifespan of the RBCs. Caution should be exercised when interpreting the HbA1c results from patients with these conditions.
This assay is not useful in determining day-to-day glucose control and should not be used to replace daily home testing of blood glucose.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Nathan DM, Kuenen J, Borg R, et al: Translating the A1c assay into estimated average glucose values. Diabetes Care 2008 Aug;31:1473-1478
2. Goldstein DE, Little RR, Lorenz RA, et al: Tests of glycemia in diabetes. Diabetes Care 2003 Jan;26:S106-S108
3. American Diabetes Association: Standards of medical care for patients with diabetes mellitus. Diabetes Care 2009 Jan;32:S1
Method Description Describes how the test is performed and provides a method-specific reference
The BIO-RAD Variant II Turbo Hemoglobin A1c Program utilizes principles of ion-exchange HPLC. The samples are automatically diluted on the Variant II Turbo Sampling Station (VSS) and injected into the analytical cartridge. The Variant II Turbo Chromatographic Station (VCS) dual pumps deliver a programmed buffer gradient of increasing ionic strength to the cartridge, where the hemoglobins are separated based on their ionic interactions with the cartridge material. The absorbance at 415 nm is measured. An additional filter at 690 nm corrects the background absorbances. The Bio-Rad in2it, a boronate-affinity chromatography method, is used when the Variant II Turbo does not produce reliable results. Both methods are certified by National Glycohemoglobin Standardization Program as having documented traceability to the DCCT reference method.(Instruction Manual: Bio-Rad Variant II Turbo Hemoglobin A1c Program, L70245800, Hercules, CA, March 2006)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Sunday; Continuously
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|HBA1C||Hemoglobin A1c, B||4548-4|