ECONOMIC-EVALUATION OF INSULIN LISPRO VERSUS NEUTRAL (REGULAR) INSULIN THERAPY USING A WILLINGNESS-TO-PAY APPROACH

This willingness-to-pay (WTP) analysis is the first study of its kind undertaken in Australia to support an application for listing of a new drug on the Australian national formulary. The technique offers the a dvantage of being able to summarise diverse outcomes of therapy in a s ingle unit of measure. Willingness to pay is used to value benefits in cost-benefit analysis (CBA), and CBA represents an absolute decision rule. An open-ended question with a bid-up approach was used to minimi se bias and elicit the maximum amount patients would be willing to pay for insulin lispro. The WTP study incorporated scenarios describing t he outcomes from insulin lispro and neutral (regular) insulin, the res ults from a formal metaanalysis and a description of the injection cha racteristics of the therapies. A sample of 83 patients with type I or II diabetes mellitus were surveyed using an open questionnaire to dete rmine their maximum willingness to pay for the therapy they preferred. Overall, 92% of patients preferred insulin lispro (referred to as ins ulin A) and 8% preferred neutral insulin (referred to as insulin B). T he incremental benefit per patient was calculated as 452.16 Australian dollars ($A) per year. Insulin lispro was listed on the Australian na tional formulary at a 36% premium over neutral insulin, so the additio nal cost per patient would be $A70.32 per year. Therefore, costs were exceeded by the benefits and insulin lispro was deemed to offer a net benefit. A multivariate analysis indicated that those patients who wer e middle-aged had the strongest preference for insulin lispro.