Genetic tests that may replace biopsies

Apr 23 2010

By Candy Lashkari

Genetic tests conducted on blood samples may replace the current biopsies when it comes to checking if immune systems are rejecting new organs of heart transplant patients. The test would be far less invasive and uncomfortable as compared to the biopsies, not to mention more affordable.

The test is called AlloMap and was developed by a private company in Brisbane, Calif called XDx. As per the authors the trial was too small and too brief to allow firm conclusions, but the study will be presented on Thursday in Chicago at the annual meet of the International Society for Heart and Lung Transplantation. It has already been published online by the New England Journal of Medicine.

After a heart transplant one fourth of the recipients may have a rejection episode despite using immune suppressing drugs. These episodes can be successfully treated with drugs but can damage the heart if treatment is not timely. In some cases the rejection can be fatal. So biopsies are performed regularly to keep an eye on the condition about once a week after a transplant.

In this procedure a tube is inserted into a vein in the neck and sent down to the heart to pick up heart tissue to be studied under a microscope. Less invasive methods to detect rejection have been a constant effort. Imaging has also been used to try and detect rejection by the body of the new organ. However genetic technology has offered a very viable method with the AlloMap test.

"Among selected patients who had received a cardiac transplantation more than six months previously and who were at a low risk for rejection, a strategy of monitoring for rejection that involved gene-expression profiling, as compared with routine biopsies, was not associated with an increased risk of serious adverse outcomes and resulted in the performance of significantly fewer biopsies," write Michael X. Pham, MD and colleagues from the Stanford University Medical Center in California.

The study was conducted on 602 patients at 13 American transplant centers. They had received a new transplant organ in the previous six months to five years. Half were given biopsies and half the blood tests at the same frequency. The test analyses the activity level of 11 genes and computes a score indicating the likelihood that rejection is occurring.

Dr. John A. Jarcho, a deputy editor of The New England Journal, said in a commentary in the journal that this was the first time that clinical trials were used for such a technique to evaluate outcomes for patients. He also questioned the need for routine screening for rejection based on the fact that some transplant centers have already reduced the number of biopsies conducted after a transplant. May be in the near future biopsies will no longer be used to determine rejections.