Paper Standard Gamble: the reliability of a paper questionnaire to assess utility.

BACKGROUND

Quality of life is often best estimated by standard gamble techniques. However, these techniques usually require time-consuming and expensive interviews or computer-directed questionnaires. Paper Standard Gamble (PSG) is a paper questionnaire that has previously been shown to accurately represent standard gambles elicited by computer. The authors sought to demonstrate its test-retest reliability in comparison to other, paper-based measures of quality of life.

METHODS

The authors used a longitudinal cohort design with duplicate assessments of quality of life by PSG, the Dermatology Life Quality Index, and the Mental and Physical Component Summary scores of the SF-12 in stable dermatology out-patients. Baseline measures were performed by mail 1 to 2 weeks before a scheduled dermatology clinic visit. Follow-up measures were performed in the waiting room before being seen by the dermatologist. The authors calculated the coefficient of variation and the Spearman rank correlation coefficient for each of the instruments.

RESULTS

74 patients with stable skin conditions participated. The coefficient of variation of PSG (0.47%) was smaller than the other instruments (4.26%-5.22%); PSG's correlation was higher (0.97 v. 0.65-0.80).

CONCLUSION

PSG, a 1-page paper questionnaire, is a reliable measure of patient utility suitable for use in postal surveys.