Equation can identify medication nonadherence and those at risk for rejection.

PHILADELPHIA—Researchers have developed a new and simple way to monitor nonadherence to immunosuppressive medications and predict an increased risk of graft rejection in pediatric renal transplant patients.

Adolescents are at high risk of not taking their medications and the new tool “can help identify patients who are at risk for rejection,” said investigator Hilda E. Fernandez, MD, a pediatric nephrology fellow at the University of California at Los Angeles (UCLA) David Geffen School of Medicine.

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In pediatric liver transplant patients, previous research has shown that increased standard deviation (SD) in tacrolimus (FK) trough levels correlates with higher rates of acute rejection. However, this has not been studied in pediatric renal transplant patients.  Previous UCLA studies looking at SD of FK and mycophenolate mofetil (MMF) levels in pediatric renal transplant patients showed inconclusive results.

In this study of 46 patients (mean age 13.7 years), the investigators used coefficient of variation (CV= [SD ÷ mean] × 100%) to eliminate confounding factors. All subjects underwent renal transplantation between 2002 and 2003. Thirty-seven patients received steroids and the remaining nine did not. Ten had biopsy-proven rejection. The time to first rejection averaged 3.7 years after transplantation.

FK and MMF trough levels were measured serially from one to 12 months post transplant. The median FK SD was 4.8 in patients with rejection and 3.1 in patients who did not suffer rejection. The median CV was higher in patients with rejection compared with patients who did not have rejection.

Researchers observed no difference in the median FK, SD, or CV between living and deceased donor transplants, or between steroid vs. no steroid use. The median MMF CV was 45.1% in patients with rejection and 51.9% in patients without rejection.

A high FK CV predicted an increased risk for graft rejection, presumably because of nonadherence to medication regimens. MMF CV was not associated with graft rejection.

“This is the first time a study has looked at this method,” Dr. Fernandez said. “It could become an easy method for identifying patients who may be at risk for rejection and may need an earlier renal biopsy.”

Dr. Fernandez reported findings here at the American Society of Nephrology’s Renal Week conference.