A blood test that analyzes genetic activity could let heart transplant patients avoid many of the invasive and uncomfortable biopsies now used to monitor whether their immune systems are rejecting their new organs, doctors said in a study published Thursday.
The study found that patients who were monitored for rejection using the blood test had outcomes roughly equivalent to those of patients who were given frequent heart biopsies. The test, called AlloMap, was developed by XDx, a privately held company in Brisbane, Calif.
“I think it will cause a paradigm shift in the way we look at monitoring for rejection,” said Dr. Michael Pham, a clinical assistant professor of cardiovascular medicine at Stanford and a leader of the study.
Still, the authors of the study acknowledged that the trial was too small and too brief to allow for firm conclusions. It also excluded very recent transplant recipients, who have the highest risk of rejection.
The study, paid for by XDx, was to be presented in Chicago on Thursday at the annual meeting of the International Society for Heart and Lung Transplantation and was published online by The New England Journal of Medicine. Some authors of the study, but not Dr. Pham, received consulting fees from XDx and one was an employee of the company.
Despite the use of immune-suppressing drugs, about one-quarter of heart transplant recipients have a rejection episode requiring treatment in the first year after the transplant. While such episodes can be treated by drugs, they may damage the heart, especially if the treatment is not started soon enough. In some cases the rejections prove fatal.
Some transplant centers perform biopsies as often as once a week after the transplant, and as often as every few months for the next several years. A tube is inserted into a vein in the neck and threaded to the heart to pick up pieces of heart tissue to be examined under a microscope.
Efforts have been made to develop less invasive approaches to detect rejection, including use of imaging, and the AlloMap test was approved for this use by the Food and Drug Administration in 2008. But this is the first time such a technique was subject to a clinical trial evaluating the outcomes for patients, Dr. John A. Jarcho, a deputy editor of The New England Journal, said in a commentary in the journal.
AlloMap is an example of the sophisticated and expensive tests — it costs $3,000 each time — being developed using new genetic technology. The test analyzes the activity level of 11 genes and computes a score indicating the likelihood that rejection is occurring.
The study involved 602 patients at 13 American transplant centers who had received a transplant from six months to five years earlier. Half were given periodic biopsies and the others the blood test at the same frequency.
While the genetic test is cheaper than a biopsy, which costs $4,000 to $5,000, it is still unclear if the strategy would save money over all, Dr. Pham said.
The least expensive approach might be to conduct less testing of either type. Only 6 of the 34 episodes of rejection in the group getting the genetic test were found solely by the test. The rest were detected by echocardiogram or because of symptoms.
Dr. Jarcho, in his commentary, said those results raised the question of whether routine screening for rejection was even needed. Some transplant centers have already scaled back the number of biopsies they do. By Andrew Pollack, The New York Times
