On 3 July 2013, the American National Institute of Health (NIH) announced that it had developed "a non-invasive urine-based […] test to detect whether a graft kidney will be rejected". In actual fact, the test "measures the levels of three biomarkers present in a patient’s urine to establish whether the recipient’s immune system is in the process of reacting against the graft cells, thereby triggering rejection and transplant failure".
This new test will eventually replace the kidney biopsy which is currently the only technique used "to determine whether graft rejection is in progress". The biopsy is invasive because it "triggers bleeding and pain" and "cannot therefore be carried out repeatedly as a preventive measure".
Scientists have focused on developing a new "non-invasive technique to detect activation of a patient’s immune system" for several years. "This will allow doctors to identify the precursors of organ rejection", and "individualise treatment for each transplant patient". Thanks to this test, "researchers have been able to determine with 85% accuracy whether a transplant is viable or about to be rejected". These results have been confirmed by biopsies. Researchers have thus proved that "if the urinary levels of the three biomarkers exceed a certain threshold, the patient’s immune system is in the process of attacking the transplant cells, gradually leading to rejection". Furthermore, once the threshold has been exceeded, they noted that "the levels of the three biomarkers increased slowly and progressively over several weeks before dramatically increasing […] approximately 20 days before total kidney rejection". Consequently, researchers have used this test to show that total kidney rejection can be diagnosed almost three weeks in advance. This test is therefore a clear indicator of future rejection.
During the next stage, researchers wanted to conduct a new study so that doctors could use the urine-based test to increase "immunosuppressant treatment for patients during phases of potential rejection" and thus prove or disprove "the efficacy of this method in preventing kidney destruction".