Age-related differences in renal function at onset of renal replacement therapy in chronic kidney disease stage 5...

Guidelines for initiating renal replacement therapy (RRT) are based on renal function and not age, so renal function at onset of RRT is expected to be similar across age groups.

To evaluate renal function at initiation of RRT across age groups.

Observational cross-sectional study.

We extracted data for all incident chronic kidney disease (CKD) stage 5 patients (n = 322 064) commenced on chronic dialysis (haemodialysis and peritoneal) and renal transplant in the US from 1995 to 1999 from the US Renal Data Systems (USRDS). Subjects (n = 662) with incomplete data were excluded. The reminder (n = 321 402) were classified into five age groups: 0-19 years; 20-44 years; 45-64 years; 65-74 years; >/=75 years. Mean values of serum creatinine (Cr, mg/dl), creatinine clearance (CrCl, ml/min), body weight (kg) and body mass index (BMI, kg/m(2)) at onset of RRT were computed. Mean daily urinary creatinine excretion per kg body weight (CrCl x Cr/0.07/weight) was also calculated.

Progressively lower serum creatinine levels were found in adult patients with increasing age (10.70, 8.56, 7.38 and 6.88 mg/dl in those aged 20-44 years, 45-64 years, 65-74 years, >/=75 years, respectively). CrCl was also lower in the same groups (14.76, 13.38, 11.63 and 11.60 ml/min, respectively).

Older patients have a greater reduction in renal function than younger patients at onset of RRT, suggesting a delay in initiation of therapy.