As more patients start dialysis at earlier stages, those with a higher estimated glomerular filtration rate (GFR) at dialysis initiation appear to be at increased risk of death, reports a study in Canadian Medical Association Journal.
The analysis included Canadian Organ Replacement Register data on 25,910 adult patients starting dialysis between 2001 and 2007. Cases with an estimated GFR above 10.5 mL/min per 1.73 m2 at the start of dialysis were defined as early initiators. Trends in GFR at the start of dialysis were assessed, and the risk of death was compared for patients with early versus late initiation of dialysis.
Mean estimated GFR at the start of dialysis increased during the period studied: from 9.3 mL/min per 1.73 m2 in 2007 to 10.2 mL/min per 1.73 m2 in 2007. Meanwhile, the percentage of patients with early initiation increased from 28 percent to 36 percent. Mean GFR was 15.5 mL/min per 1.73 m2 among early initiators versus 7.1 mL/min per 1.73 m2 for late initiators.
Early initiators were at increased risk of death: unadjusted hazard ratio (HR) 1.48. The association was weakened but still significant, HR 1.18, after adjustment for demographic factors, serum albumin level, cause of end stage renal disease, type of vascular access, late referral, and transplant status. The difference in mortality between early and late initiators narrowed after one year. However, the gap started to widen again at 24 months, and remained significant at 30 and 36 months.
In Canada and elsewhere, dialysis is being initiated in patients with higher estimated GFRs. In contrast to the belief that early initiation of dialysis may lead to some advantage in patient outcomes, recent studies have found no survival benefit of starting dialysis at a higher GFR.
The new report provides evidence that patients starting dialysis at a higher GFR are at higher risk of death than those with later initiation of dialysis. The association is attenuated, but remains significant after adjustment for baseline characteristics. Rigorous studies are needed to develop evidence-based guidelines for the optimal timing of dialysis initiation [Clark WF, et al. Association between estimated glomerular filtration rate at initiation of dialysis and mortality. CMA 2011; 183:47–53].