Analysis of three biomarkers in the urine of kidney transplant recipients can diagnose — and even predict — transplant rejection, according to results from a clinical trial....This test for biomarkers ...offers an accurate, noninvasive alternative to the standard kidney biopsy....The findings appear in the July 4 issue of the New England Journal of Medicine.....Following a kidney transplant, patients receive therapy to prevent their immune systems from rejecting the organ. Even with this immunosuppressive therapy, approximately 10 to 15 percent of kidney recipients experience rejection within one year after transplantation. Typically, a biopsy is performed only after a transplant recipient shows signs of kidney injury. Although the procedure seldom causes serious complications, it carries some risks, such as bleeding and pain. In addition, biopsy samples sometimes do not give doctors an accurate impression of the overall state of the kidney because the samples are small and may not contain any injured tissue.....In the study...investigators at five clinical sites collected urine samples from 485 kidney transplant recipients from three days to approximately one year after transplantation. Researchers...assessed the urinary cell levels of several biomarkers that previously have been associated with rejection. Statistical analysis revealed that a group of three urinary biomarkers formed a diagnostic signature that could distinguish kidney recipients with biopsy-confirmed rejection from those whose biopsies did not show signs of rejection or who did not undergo a biopsy. The biomarkers include two messenger RNA molecules that encode immune system proteins implicated in transplant rejection and one noncoding RNA molecule that participates in protein production. The researchers used the signature to assign values to each urine sample and identify a threshold value indicative of rejection. With this test, they could detect transplant rejection with a high level of accuracy.
As emphasized in this article, the use of diagnostic signature of three urinary biomarkers seems to offer a better alternative to assessing the status of a transplanted kidney than the current gold-standard, a kidney biopsy. Although such biopsies usually do not result in serious complications, kidney biopsies are not undertaken lightly and, as noted above, may not yield tissue that accurately represents what is happening to adjacent tissue (sampling error). These is also considerable expense associated with a biopsy. However, there will also be a cost for the biomarker testing.
It's important to note, and as noted above, that there is the distinct possibility that the biomarker signature may be able to predict future rejection of the kidney and prompt a change in the immunosuppressive therapy to save the organ. This is also possible with a biopsy but the biomarkers may prove to be better at this, more quantitative, and can be repeated frequently. Although the kidney is the most commonly transplanted organ, I am sure that this biomarker approach is being evaluated for other transplanted organs but with serum used as the analyte and not looking at the same biomarkers.