Molecular Assay Approved for Blood Compatibility Testing

Troy Brown, RN

May 22, 2014

The US Food and Drug Administration (FDA) approved the Immucor PreciseType Human Erythrocyte Antigen Molecular BeadChip Test (BioArray Solutions Ltd) on May 21. The test is the first FDA-approved molecular assay used in transfusion medicine to help determine blood compatibility.

It can be used to determine non-ABO/non-RhD (non-ABO) red blood cell types in donor and patient blood in the United States.

The surfaces of red blood cells contain minor blood group antigens as well as the major ABO blood group antigens. Some individuals develop antibodies to non-ABO antigens after transfusion or pregnancy. People who receive repeated blood transfusions, such as those with sickle cell disease, are particularly vulnerable. The development of these antibodies can cause red blood cell destruction if the patient later receives transfused blood with the corresponding antigens.

This can be prevented by selecting blood that is more closely matched to the patient's non-ABO antigens. In a potential transfusion recipient who has an antibody known to cause red blood cell destruction, red blood cells without the corresponding antigen must be found.

Such testing has traditionally been performed by serological typing: testing the blood with reagents (antisera) that are specific for the antigens being tested for in the blood. Specific antisera may be scarce or unavailable, however. This test provides a new method for identifying non-ABO antigens on red blood cells.

The approval of the test "provides an alternative to serological typing and may enhance patient care in certain situations," said Karen Midthun, MD, director of the FDA's Center for Biologics Evaluation and Research in an FDA news release.

The test detects genes that control the expression of 36 antigens that can be present on the surface of red blood cells. "The test uses thousands of coded beads that bind with the genes coding for non-ABO red blood cell antigens that are present in a blood sample. A light signal is generated from each bead that has captured a specific gene," the FDA release explains. "Accompanying computer software decodes the light signals and reports which antigens are predicted to be present on the red cells based on the genes that are detected."

In a study that compared the typing results of the test with licensed serological reagents and DNA sequencing, the test performed comparably to the other methods.


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