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Blood test can predict risk of heart transplant rejection without biopsy

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A heart transplant can restore health to an individual with a failing heart. Currently, in the US, approximately 2,000 patients a heart transplant each year. A major problem with any organ transplant is rejection; thus, tests that can evaluate rejection are of utmost importance. UCLA researchers have reported that a blood test commonly used to determine whether heart transplant recipients are rejecting their new organ can also predict rejection-related problems that may occur months before the actual rejection process occurs. They published their findings online in the journal Transplantation.

Until recently, the only way to diagnose rejection was to perform a heart muscle biopsy, which is a painful and potentially risky procedure that involves inserting a heart catheter through a neck vein. The UCLA investigators reported that the AlloMap test, which evaluates a blood sample for changes in the expression of 11 genes, can be used over a period of time to assess the risk of dysfunction or rejection of a transplanted heart; the determination can be made months before such an event may occur.

“For the first time, we can use genomic testing over multiple patient visits to go beyond intuition to understand not just how patients are doing now but how they are likely to be a few months from now,” explained principal investigator Dr. Mario Deng, medical director of UCLA’s Integrated Advanced Heart Failure–Mechanical Support–Heart Transplant Program. He added, “It’s another step toward personalized medicine.”

The investigators explain that the discovery that transplant recipients’ white blood cells contain this predictive information regarding rejection, independent of how their transplanted heart may be currently functioning, has the potential to improve care and outcomes. They note that their findings mark a major step in the movement toward using genomic-based testing to predict future clinical events; in addition, it can enhance the benefits of similar tests being developed for recipients of other organs.

In 2008, the AlloMap gene-expression profiling test received clearance from the Food and Drug Administration (FDA). It is now routinely used by a majority of US heart transplant centers to monitor low-risk patients during follow-up care; the major benefit is that it results in a marked reduction of heart biopsies. The test is based on research Dr. Deng led in collaboration with more than a dozen of the largest US heart transplant centers and the biotech company XDx (Brisbane, California). It measures the expression levels of 11 genes from a patient’s blood sample; each of these genes are known to be associated with rejection risk. Dr. Deng explained, “The AlloMap was the first FDA-cleared test allowing transplant centers to rule out rejection at the time of the visit. But until now, it has never been used to predict future events.”

The current study has its roots in data originally collected by major US transplant centers that was published in the New England Journal of Medicine in 2010. In that study, 600 heart transplant patients were randomly assigned to be monitored for potential episodes of rejection either through a routine biopsy or through the AlloMap test. The study found that AlloMap was just as effective as a biopsy for the detection of rejection or dysfunction; in addition, it significantly increased patient satisfaction because it was less invasive.

The new study adds to the prior one because it demonstrates for the first time the ability of the AlloMap test, when used over time, to predict future events. The study authors note that using gene-expression profiling to predict the probability of future rejection-related problems with their transplanted heart could change the way such patients are treated. For example, transplant patients deemed to be at low risk for adverse events could be given lower doses of immunosuppressive drugs; the benefit would be a reduction in major side-effects from the drugs. Conversely, patients at high risk for rejection could be evaluated at shorter time intervals for rejection.

At present, similar tests are not available to monitor the potential for rejection in other types of transplanted organs; however, Dr. Deng noted that active collaborative and multidisciplinary research programs at UCLA and elsewhere are striving to bring genomic testing to these fields.