What is a HLA test?

Last Modified: September 13, 2019  |   Created on: May 2, 2019
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HLA test is Human Leukocyte Antigen test, also known as Tissue typing or Histocompatibility testing. They are specialized proteins present on the surface of all cells in the body. The HLA genes that people inherit are the reason for the HLA antigens present on their cells.


When is HLA test required?

Most often, prior to selecting a suitable donor for an organ or bone marrow transplant and for transplant recipients primarily to match up donors and recipients of organ and bone marrow transplants.

What is tested in a HLA test?

A pattern of antigens, called a tissue type, is inherited from your parents. Half comes from your mother and half comes from your father. Everyone has their own pattern except for identical twins, who have the same pattern and are an identical match for tissue and blood cells. Brothers and sisters who have the same parents have a 1 in 4 chance of being an identical match.

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What does the HLA test results mean?

Specific MHC antigens are identified during HLA typing for organ and tissue transplant compatibility. The genes and/or antigens of transplant recipients are compared to those of potential donors. Results indicate how many antigens match or how many mismatches are present. The greater the number of matches the more likely the transplant will succeed. “0 mismatches” indicates a high probability that the organ or tissue will not be rejected by the recipient.

The absence of HLA antibodies to the donor HLA is very important. Matching a donor with a recipient who has developed antibodies must be carefully considered because the more HLA antibodies a person has developed, the higher the probability for rejection.

A positive (reactive) crossmatch result is usually interpreted as a high risk transplant. These patients are at risk for rejection of the transplant, which may or may not be treatable with various immunosuppressant drugs.

Rules for HLA matching

There are rules for the minimum, or lowest, HLA match needed between a donor and patient. Research shows that patients have better outcomes (results) with a closely matched donor.These are a few matching rules:

Rules for HLA matching For a haploidentical (half-matched) transplant, donors match exactly half, or 5 of 10, HLA markers.For a fully matched transplant, donors match more than 5 of 10 HLA markers.The donor is usually the patient’s parent or child.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes, for HLA typing, a swab of cells is collected from the inside of the cheek (a buccal swab). Here is the Step by Step Guide to HLA Buccal Swab test

Why is HLA Typing important?

HLA matching promotes the growth and development of new healthy blood cells (called engraftment) and reduces the risk of a post-transplant complication called graft-versus-host (GVHD) disease.

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