COMPARING OUTCOMES IN RENAL REPLACEMENT THERAPY - HOW SHOULD WE CORRECT FOR CASE-MIX

The need to evaluate the effectiveness of clinical practice to justify expensive therapy in the face of financial constraints in all areas o f health care delivery makes it necessary to identify groups of patien ts who are likely to benefit most from treatment. Various risk stratif ication methods have been used for analyzing survival probabilities fo r patients receiving renal replacement therapy. Complicated risk strat ification methods produce large numbers of risk groups of small sizes, which makes comparison between individual centers difficult. We compa red three simple methods of risk stratification, that divided patients into low-, medium-, and high-risk groups, in a cohort of 1,407 patien ts who commenced renal replacement therapy in five European countries during a 7-year period. Method 1 considered age (>55 years) and diabet es alone; method 2 used a higher age limit (>70 years) and comorbid il lnesses, including those other than diabetes; and method 3 used only t he number of comorbidities (none, 1, or greater than or equal to 2) fo r stratification. Kaplan-Meier survival curves were constructed for co mparison between risk groups and Cox's regression model used to assess strength of relationship with mortality. Although patient survival wa s significantly different between the low-, medium-, and high-risk gro ups using all three methods, Cox's regression analysis showed that met hod 2 provided the greatest discrimination between risk groups. In pre dicting mortality, method 2 (based on comorbidities and age) showed th e highest sensitivity and specificity (84% and 80%, respectively) comp ared with method 1 (80% and 74%) and method 3 (64% and 82%). Validatio n of this approach in other populations in a prospective study is requ ired before this method, which takes into account the influences of bo th age and comorbidity for risk stratification, can be used for compar ing survival data and for presenting results of renal replacement ther apy. (C) 1998 by the National Kidney Foundation, Inc.