Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

HBA1C
82080
H63D is insufficient to cause clinically significant iron overload in the absence of additional modifying
factors. However, compound heterozygosity for C282Y/H63D has been associated with increased
hepatic iron concentrations. Approximately 1% to 2% of individuals with this genotype will develop
clinical evidence of iron overload. While individuals with this genotype may have increased iron
indices, most will not develop clinical disease without comorbid factors (steatosis, diabetes, or excess
alcohol consumption). The clinical significance of a third HFE mutation, S65C (exon 2, 193A>T),
appears to be minimal. This rare variant displays a very low penetrance. Compound heterozygosity for
C282Y and S65C may confer a low risk for mild HH. Individuals who are heterozygous for S65C and
either the wild-type or H63D alleles do not seem to be at an increased risk for HH. The S65C mutation
is only reported when it is part of the C282Y/S65C genotype. Refer to What's New in Hereditary
Hemochromatosis, Mayo Medical Laboratories Communique 2005 April;30(4) for more information
regarding diagnostic strategy. See algorithm in Special Instructions.
Useful For: Establishing or confirming the clinical diagnosis of hereditary hemochromatosis (HH) in
adults HFE genetic testing is NOT recommended for population screening Testing of individuals with
increased transferrin-iron saturation in serum and serum ferritin With appropriate genetic counseling,
predictive testing of individuals who have a family history of HH
Interpretation: An interpretive report will be provided. For more information about hereditary
hemochromatosis testing, see Hereditary Hemochromatosis Algorithm in Special Instructions.
Reference Values:
An interpretative report will be provided.
Clinical References: 1. Mura C, Raguenes O, Ferec C: HFE Mutations analysis in 711
hemochromatosis probands: evidence for S65C implication in mild form of hemochromatosis. Blood
1999;93(8):2502-2505 2. Beutler E, Felitti VJ, Koziol J, et al: Penetrance of 845G->A (C282Y) HFE
hereditary haemochromatosis mutation in the USA. Lancet 2002;359(9302):211-218 3. Walsh A, Dixon
JL, Ramm GA, et al: The clinical relevance of compound heterozygosity for the C282Y and H63D
substitutions in hemochromatosis. Clin Gastroenterol Hepatol 2006;4(11):1403-1410 4. Whitlock EP,
Garlitz BA, Harris EL, et al: Screening for hereditary hemochromatosis: a systematic review for the U.S.
Preventive Services Task Force. Ann Intern Med 2006;145(3):209-223
Hemoglobin A1c, Blood
Clinical Information: 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
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