Willingness to pay and time trade-off: useful utility indicators for the assessment of quality of life and patient satisfaction in patients with port wine stains

Abstract

For cost utility analyses in health economic research it is necessary to assess quality of life for content validation. Previously, both quality of life questionnaires and utility indicators such as willingness to pay and time trade-off have been used successfully in patients with chronic skin diseases, such as psoriasis vulgaris or atopic eczema. For the first time to assess willingness to pay and time trade-off in patients with port wine stains, and to study possible correlations between these indicators, patient income, quality of life questionnaires and subjective or objective outcome measures. The results of a survey on 36 patients with facial lesions who had completed laser treatment were used for assessments. The 'Chronic Skin Disease Questionnaire' (CSDQ) and the 'Short Form-36 Health Survey' (SF-36) were used as quality of life questionnaires. Special questions were used as a basis for calculating the utility indicators, willingness to pay and time trade-off. Completed questionnaires were sent back by 25 patients (69%). Willingness to pay and time trade-off were used as instruments for the assessment of quality of life [questions answered by 23 (92% of respondents)]; patients were willing to pay 11.8% of their monthly income and would offer a mean value of 1.2 h per day for an imaginary therapy leading to complete cure of the skin problem. Statistical correlation analyses were not performed because this pilot study included only a small number of patients. Frequency distributions show no apparent correlation between willingness to pay and patients' profession (used as a surrogate for income). Possible correlations were seen between willingness to pay, time trade-off, the scales 'anxiety/avoidance' and 'helplessness' of the CSDQ as well as 'social function' of SF-36 and subjective or objective efficacy. Twenty-nine patients (80%) were willing to pay for the treatment, a surrogate measure for patients' satisfaction with treatment modality. Overall, patients would pay an average of 16.0 euros per single treatment and 192.0 euros for the whole course of treatments. In contrast with patients who evaluated treatment modality as excellent or very good (willingness to pay for single treatment, euro 22.0; for whole treatment, 270.0 euros), patients who judged treatment good (8.0 euros, 145.0 euros), moderate or bad (12.0 euros, 146 .0 euros) were willing to pay markedly less. (i) The questions for willingness to pay and time trade-off were understood by most patients and produced meaningful answers. (ii) There were apparent correlations between the utility indicators, subjective or objective outcome and the scales of the quality of life questionnaires. (iii) The results show that these indicators have a high potential for use in this dermatological condition, especially as a basis for health economic evaluations.