Quality of Life during the Treatment of Gallstone Disease: Issues in the Development of Health State Descriptions.

There are three main options for the treatment of gallstone disease, namely open cholecystectomy, laparoscopic cholecystectomy and extracorporeal shockwave lithotripsy. An economic evaluation of these was undertaken. Because the three options have serious but different effects upon the quality of life (QoL) the study design was a cost utility analysis (CUA). In such a design the output of each intervention is measured in quality adjusted life years (QALYs) or healthy year equivalents (HYEs). Measurement of these require the construction of valid health state scenarios. The objective of the present paper is to describe these scenarios and the issues arising from this. Other results and issues from the project are present in Street (1993), Cook and Richardson (1993), and Cook, Richardson and Street (1993a; 1993b). In the paper a variety of methodological issues are discussed that are associated with the construction of the health state scenarios. First, an issue overlooked in the literature to date is that health state values change with the underlying perspective or value basis adopted by the researcher. This has typically been an ex post perspective in which the quality of life actually experienced is measured at a point in time. The alternative is an ex ante perspective in which the patient's anticipated outcome and considerations of risk aversion become relevant. Secondly (and to a greater or lesser extent in common with most economic analyses in the health sector) the patient experience cannot be inferred from the clinical outcome and, at present, the long run clinical consequences of the various treatments are uncertain. Thirdly, in the absence of a universally accepted method for constructing health states scenarios the conversion of qualitative and survey QoL information into scenarios appropriate for cost utility analysis remains problematic. The paper outlines the three treatment options for gallstone disease. It describes the patient experience as obtained from interviews and a postal questionnaires and how the final health state descriptions were derived from this. It is concluded that there is a need for a general instrument which in the context of life and quality of life judgements about resource allocations itself is cost effective, as well as valid and sensitive to changes in quality of life factors across a wide range of diseases.