Reconciling decision models with the real world - An application to anaemia of renal failure

Objective: The choice of evidence used in decision modelling of healthcare interventions divides analysts into 2 groups: (i) those who favour randomis ed clinical trial (RCT) data; and (ii) those who prefer 'real world' data. This preference may have serious consequences if the end result is to infor m healthcare policy. This paper uses Medicare coverage of epoetin-alpha [er ythropoietin (EPO)] as a case study to illustrate a technique which can be used to overcome some of the bias inherent in RCT data while avoiding some of the common pitfalls associated with the use of observational data. Design and setting: Cost analysis of 2 treatments for anaemia of renal fail ure primarily in an outpatient setting is modelled in a decision tree. This method can be used to analyse healthcare interventions or policies in any setting. Patients and participants: Patients with nontransplanted end-stage renal di sease (ESRD) who received either EPO or blood transfusion for treatment of anaemia at any time during the 1-year study period (July 1989 to June 1990) were included in the sample. Methods: Outcome effects in the natural setting are decomposed into 2 parts : a treatment effect and a population effect. This is then extended to the special case of policy analysis. Logistic and multiple regression are used to estimate branch probabilities and payoffs, respectively, for 2 treatment options. Main outcome measures and results: Under standard methods of decision analy sis, an increase of $US7032 per patient following EPO coverage is observed. With the decomposition technique, the policy effect is estimated to be les s, $US6172, the difference coming from the population effect. Conclusions: Failure to remove population effects from observed outcome eff ects may lead to biased decision-making. Although not directly observable, the population effect can be imputed from secondary data. The decomposition and imputing technique allows for a more meaningful interpretation of the results for the purpose of policy analysis.