Measuring health-related quality of life outcomes in women with endometriosis: results of the Gynaecology Audit Project in Scotland

The clinical management of endometriosis was addressed within the recent Gynaecology Audit Project in Scotland. The impact of endometriosis and its treatment on women's health-related quality of life was examined using a condition-specific measure and a general measure, the Short Form 36 health survey (SF-36). Postal questionnaires containing the health-related quality of life measures were sent to 273 women at diagnosis and six months later. The measurement properties, including the reliability, validity and responsiveness, of the measures were examined. The condition-specific questions and the SF-36 had a high level of reliability. The validity of the condition-specific scores was demonstrated by their high correlation with the SF-36 which is a well-validated measure. Furthermore, the condition-specific scores were related to clinicians' assessment of disease severity and the need for further treatment. At the six month follow-up, changes in scores conformed to expected hypotheses, demonstrating the responsiveness of both measures. As a general measure, the SF-36 appeared to reflect the effects of both the condition of interest (i.e. endometriosis) and other conditions affecting health at the time of measurement (i.e. treatment side effects). The condition-specific measure was more responsive than the SF-36 to the changes in pain symptoms which resulted from active treatment. A condition-specific questionnaire, together with a general measure such as the SF-36 health survey, can provide a reliable, valid and responsive package of measures for assessing health-related quality of life in women with endometriosis. Such measures should be used alongside clinical measures of outcome to assess the effectiveness of different treatment strategies for endometriosis. A similar approach combining general and specific instruments would be useful in medical audits of other conditions.