Predicting survival in adults with end-stage renal disease: an age equivalence index

To quantify prognosis in patients with end-stage renal disease, we evaluated pretreatment clinical state and ascertained the outcome of all 220 patients who began therapy at two hospitals from 1970 to 1975. Each of three pretreatment characteristics made a statistically significant independent contribution to the relative risk of death: age (relative risk for 10-year increments = 2.2, p less than 0.001); duration of diabetes (relative risk for 10-year increments = 2.2, p less than 0.001); and left-sided heart failure (relative risk = 2.0, p less than 0.001). We combined the effects of these factors in an age-equivalence index that showed a strong gradient in survival rates from lower to higher values; the 5-year survival rate differed between 92% in patients with a score of 30 or less and 6% in patients with a score over 70. This index, which is simple to use, should prove helpful in patient care and can improve the scientific validity of therapeutic comparisons in patients with end-stage renal disease by identifying and adjusting for the selection biases that occur in the allocation of different treatments.