To avoid nephrotoxicity calcineurin inhibitors are frequently replaced by mTOR-inhibitors like Sirolimus (SRL). Worsening of proteinuria has been reported after conversion to mTOR-inhibitors. We aimed to assess frequency, extent and risk factors for new onset proteinuria (NOP) after conversion to SRL in a large multi center cohort.

For this retrospective analysis 10 German transplant centers collected demographic, transplant and laboratory data of all renal allograft recipients (pts) being converted to SRL between Jan 1st 2000 to Dec 31st 2008. All pts were converted to a SRL containing immunosuppression at least 90 days after transplantation (Tx). NOP was defined as urine protein concentration >500mg/l detected postconversion in pts <500mg/l preconversion. A cut off value was defined using ROC-curve analysis.

In 332 pts (69.0% male, 44.9±14 years at Tx and 5.8 ± 6.1 years post Tx) had no relevant proteinuria preconversion. In 90 pts (27.1%) NOP developed, mostly (n=57, 19.2%) within 6 months postconversion. Already at conversion pts with NOP had a significant higher urinary protein concentration (80mg/l vs. 150mg/l, p<0.005). We found that proteinuria >78 mg/l at conversion was associated with NOP (p<0.005) with an auc of 0.73, p<0.005. 24/90 pts (26.6%) developed severe proteinuria (>1500mg/l). In 115/332 pts (34.6%) SRL was stopped. The 5-year-graft-survival rate was lower in pts with NOP (74.1% vs. 84.1%, p=0.031). Patient survival was equal however. Creatinine at conversion, time from tx to conversion, sex, and year of conversion were no risk factors for NOP.

The conversion of pts with proteinuria <78 mg/l resulted in excellent long-term outcomes with a low risk of NOP. Conversion of pts with higher proteinuria should be done cautiously under close surveillance of urinary protein excretion.

Naik, M.: Grant/Research Support, Advisory Board Member. Riester, U.: Employee, Pfizer.

« Back to 2013 American Transplant Congress