|Urine test can diagnose, predict kidney transplant rejection|
|Researchers say noninvasive test will increase accuracy|
|Published Friday, July 12, 2013|
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 sponsored by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.
This test would provide an accurate, noninvasive alternative to the standard kidney biopsy, in which doctors remove a small piece of kidney tissue to look for rejection-associated damage.
“The development of a noninvasive test to monitor kidney transplant rejection status is an important advance,” said NIAID Director Anthony S. Fauci, M.D. “That will allow doctors to intervene early to prevent rejection and the kidney injury it causes, which should improve long-term outcomes for transplant recipients.”
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 injured tissue.
“Potentially, a noninvasive test for rejection would allow physicians to more accurately and routinely monitor kidney transplant recipients,” said Daniel Rotrosen, M.D., director of NIAID’s Division of Allergy, Immunology and Transplantation. “By tracking a transplant recipient’s rejection status over time, doctors may be able to modulate doses of immunosuppressive drugs to extend the survival of the transplanted kidney.”
In the study, researchers at five clinical sites collected urine samples from 485 kidney transplant recipients and 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.
To determine whether the urine test also could predict future rejection, the scientists analyzed trends in the diagnostic signature in urine samples taken in the weeks before an episode of rejection.
The values for patients who experienced rejection increased slowly but steadily leading up to the event, with a characteristic sharp rise occurring approximately 20 days before biopsy-confirmed rejection had occurred.
In contrast, the values for patients who did not show any clinical signs of rejection remained relatively constant and under the threshold for rejection. These findings suggest that it might be possible to treat impending rejection before substantial kidney damage occurs.
“The test described in this study may lead to better, more personalized care for kidney transplant recipients by reducing the need for biopsies and enabling physicians to tailor immunosuppressive therapy to individual patients,” said NIAID Transplantation Branch Chief Nancy Bridges, M.D., a co-author of the paper.
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