Changes in cost-effectiveness over time. The case of Epoetin Alfa for renal replacement therapy patients in the UK.

We analysed the factors influencing cost-effectiveness of a health care intervention over time using economic evaluations of erythropoietin as a case study. The analytical framework of a study conducted in 1990 was used to revisit the cost-effectiveness of erythropoietin. Study variables were updated to 2000 using meta-analysis, published sources, and expert opinion. After 10 years of further experience with the use of erythropoietin the cost-effectiveness ratio now falls within the range considered acceptable in the UK. The analysis shows that the vast proportion of the reduction in the cost-effectiveness ratio achieved since 1990 results from reductions in the dose and price of erythropoietin. True cost-effectiveness of a treatment can change over time, and early analysis can reach incorrect conclusions because of data deficiencies. The existence of a body such as NICE might have delayed the widespread adoption of erythropoietin in the UK, but the higher standards of clinical and economic evidence demanded by such a body might have expedited the appropriate pricing,dosage, and hence utilisation of the treatment.