Hemoglobinopathies Points to Remember

• Hemoglobinopathies are inherited hemoglobin variants caused by mutations in the globin genes.


• The people of Africa, the Mediterranean, or Southeast Asian descent are particularly at risk for hemoglobin variants


• Hemoglobin variants can confound the results of the A1C test, which indicates average blood glucose levels in the blood during the last 2-3 months.


• False A1C test results can lead to false diagnosis or over-treatment or under-treatment of diabetes in people with hemoglobinopathies.


• Information to assist in selecting the best assay methods is available from the National Glycohemoglobin Standardization Program (NGSP).


• The most common hemoglobin variants include hemoglobin S, C, and E.


• People who are homozygous for a hemoglobin variant may have a disease condition - for example, those who are homozygous for the hemoglobin S variant have sickle cell anemia. Those who are heterozygous for a variant are said to have a trait or to be carriers and are usually asymptomatic.


• A booklet for people with diabetes about hemoglobin variants and the A1C test

Hemoglobinopathies and Diabetes Effect and Diagnosis

Hemoglobinopathies

Hemoglobin molecules in red blood cells transport and distribute oxygen to cells throughout the body. Hemoglobin is composed of heme - the portion of the molecule holding iron—and globin—a protein made up of amino acid chains.

Hemoglobin variants occur when mutations in the globin genes result in changes in the amino acids of the globin protein. Hundreds of variants have been identified; a small number of variants are common and have clinical significance. Hemoglobin variants are inherited in an autosomal recessive manner.

Effect of Hemoglobinopathies on A1C Test Results

With some assay methods, A1C tests in patients with hemoglobinopathies answer in falsely high outcomes, overestimating actual average blood glucose levels for the previous 2 to 3 months. Physicians may then dicate more aggressive treatments, resulting in increased episodes of hypoglycemia. Some assay methods used with some hemoglobinopathies may result in falsely low outcomes, leading to under-treatment of diabetes. Confirmation with a fasting blood glucose is needed for a diagnosis of diabetes to prevent inappropriate treatment decisions.

When to Suspect that a Patient with Diabetes Has a Hemoglobinopathy

People who contain one gene for a hemoglobinopathy are often unaware. Several situations may show the presence of a hemoglobinopathy:
* when results of self-blood-glucose monitoring have a low correlation with A1C results
* when an A1C result is vary than expected
* when an A1C result is more than 15 percent
* when a patient’s A1C test result is radically different from a previous test result following a change in laboratory A1C methods

Diagnosis of Hemoglobinopathies

Carrier state can easily be found by hemoglobin electrophoresis. Most states now screen for common hemoglobin variants in newborns and report results. In addition, pre-pregnancy genetic testing and prenatal screening are done in some high-risk populations or in women with a family history of a variant. Screening may also be acted in parents of children with identified variants and patients with red blood cell abnormalities, such as unexplained anemia.