Urine protein test: A tipoff to kidney transplant rejection

Johns Hopkins researchers have developed the basis of an inexpensive, simple urine test that identifies impending kidney failure or rejection following transplant surgery. Their work, presented this week in a special invited lecture to the American Transplant Congress in Boston, Mass., is based on proteins found in urine, and could lead to a urine test kit that may allow many patients to skip painful biopsies.

“This has the potential to radically change the way transplant patients are managed,” says study co-author Ernesto P. Molmenti, M.D., Ph.D., associate professor of surgery at Johns Hopkins. “Frequent, noninvasive monitoring could allow doctors to better tailor immunosuppression drugs according to individual patient’s needs, prescribing lower doses to more stable patients or increasing doses for patients who show early signs of rejection.”

Molmenti estimates that the test, when developed, will be far less expensive, safer and much less painful than a standard biopsy costing hundreds of dollars in which a doctor inserts a long needle into a patient’s side to obtain a kidney tissue sample.

To build a scientific foundation for the test, Molmenti and colleagues analyzed 34 urine samples from 32 kidney patients at various stages after transplantation. Seventeen patients had organ rejection and 15 had no rejection. Rejection status was confirmed by biopsy. The researchers identified thirteen possible protein markers that were present in most of the urine samples from patients who had organ rejection, but were absent from most non-rejection samples. Three other possible protein markers were found to be lower in patients’ urine with the onset of transplant rejection. A separate analysis using a combination of biomarker candidates in a panel correctly identified 91% of the 34 urine samples.

“Unlike kidney biopsy, a urine test is risk-free, presents no discomfort or restraints to the patients, and samples the entire kidney accurately,” says study co-author William Clarke, Ph.D., assistant professor of pathology at Johns Hopkins.

Other researchers involved in the study were Benjamin C. Silverman; Zhen Zhang, Ph.D.; Daniel W. Chan, Ph.D.; and Andrew S. Klein, M.D.