Currently, the best test to check for organ rejection is a biopsy. This is an invasive procedure that is expensive and can lead to complications. In a biopsy, a probe is inserted to extract a sample of the transplanted organ. The cells in the sample are then stained and viewed under a microscope to see if they are being attacked by the patient’s immune system.

A new noninvasive test has been developed by researchers led by Hannah Valentine, a cardiologist at Stanford University, and published in Proc. Nat. Aca. Sci. Mar 2011. Their test, which is designed for heart transplant patients, relies on the fact that once the immune system begins to attack the transplanted organ, some of the cells in that organ die, are decomposed by the immune system, and carried away in the blood stream. Since the transplanted organ has different DNA than the host, the level of foreign DNA in the patient’s blood will rise. This DNA can be detected and measured using a simple blood test.

Stanford University is applying for a patent for this process and expects to license it. A good description on the development of this test appears in Tech. Rev. Mar 2011. This new test may be used in conjunction with an existing simple blood-based genetic test sold under the trade name AlloMap, that can predict which patients are most likely to have an active immune system that will lead to organ rejection. The combination of the two tests could provide a better guide for clinicians to adjust the types and dosages of immunosuppressant medications to provide transplant patients with the lowest amount needed to avoid rejection. It will also allow faster diagnosis of rejection to so that  treatment can be adjusted as needed.