Renal function as a predictor of long-term graft survival in renal transplant patients

Acute rejection is a major risk factor for kidney graft failure. However, as acute rejection has been progressively reduced by recent immunosuppressive regimens, other risk factors are becoming increasingly important. Evidence is accumulating that early renal function predicts long-term outcome. A recent registry survey of more than 100 000 kidney transplants found that 6- and 12-month serum creatinine levels, as well as the change between 6 and 12 months, are strongly associated with long-term graft survival. A survey of paediatric renal transplant recipients showed that poor creatinine clearance (<50 ml/min) as early as 30 days post-transplant predicted an annual rate of graft loss of 13% compared with <3% in patients with 30-day clearance >50 ml/min. This association between early renal function and long-term outcome was confirmed in multicentre studies. Renal transplant recipients (n=572) with 6-month serum creatinine levels >1.5 mg/dl suffered 3-year graft loss of 19.3% compared with only 8.5% in patients with levels <1.6 mg/dl (P<0.001). Significantly fewer patients receiving tacrolimus had 12-month serum creatinine levels >1.5 mg/dl compared with cyclosporin (42 versus 54%, P<0.05). Interestingly, a single-centre study (n=436) found that while glomerular filtration rate (GFR) at 6 months post-transplant had remained stable over the last decade, the rate of loss of renal function had decreased. A lower rate of GFR loss was associated with absence of rejection, use of mycophenolate mofetil rather than azathioprine and use of tacrolimus rather than cyclosporin (P<0.01). In conclusion, early measures of renal function allow identification of those patients at highest risk of graft failure and provide an invaluable tool for improving outcomes by tailored immunosuppression. The choice of such immunosuppression should be guided not only by its ability to prevent rejection, but also by its impact on renal function.