The US Food and Drug Administration has cleared for marketing a non-invasive test that uses molecular expression techniques to assist doctors in managing heart transplant patients post-surgery for potential organ rejection.

"AlloMap can help contribute to an appropriate treatment plan by identifying those patients not experiencing post-operative heart transplant rejection," said Daniel G Schultz, director of the FDA's Centre for Devices and Radiological Health. "It is an example of how advancements in science and technology are leading to new medical care diagnostics."

AlloMap measures genetic information contained in the white blood cells (cells of the immune system that defend the body against invading viruses, bacteria or other foreign material) from a patient's blood sample.

Specifically the test measures gene expression or how DNA transcribes its genetic instructions to RNA, the nucleic acid that translates and carries out those instructions of 20 different genes, resulting in a score that indicates whether a heart transplant patient is unlikely to be rejecting the new organ.

Nearly every cell of the body contains a full set of chromosomes and identical genes but only a fraction of these genes are turned on or expressed in any given cell. Gene expression occurs when certain molecular information contained within DNA is transcribed to create molecules known as RNA. These molecules in turn make the proteins that perform most of the critical functions of cells.