Development of the PsAQoL: a quality of life instrument specific to psoriatic arthritis

Background: Patient reported outcome measures used in studies of psoriatic arthritis (PsA) have been found to be inadequate for determining the impact of the disease from the patient’s perspective. Objective: To produce the PsAQoL, a PsA-specific quality of life (QoL) instrument, employing the needs based model of QoL that would be relevant and acceptable to respondents, valid, and reliable. Methods: Content was derived from qualitative interviews conducted with patients with PsA. Face and content validity were assessed by field test interviews with a new sample of patients with PsA. A postal survey was conducted to improve the scaling properties of the new measure. Finally, a test-retest postal survey was used to identify the final measure and to test its scaling properties, reliability, internal consistency, and validity. Results: Analysis of the qualitative interview transcripts identified a 51 item questionnaire. Field test interviews confirmed the acceptability and relevance of the measure. Analysis of data from the first postal survey (n = 94) reduced the questionnaire to 35 items. Rasch analysis of data from the test-retest survey (n = 286) identified a 20 item version of the PsAQoL with good item fit. This version had excellent internal consistency (a = 0.91), test-retest reliability (0.89), and validity. Conclusions: The PsAQoL is a valuable tool for assessing the impact of interventions for PsA in clinical studies and trials. It is well accepted by patients, taking about three minutes to complete, is easy to administer, and has excellent scaling and psychometric properties

Development of the ASQoL: a quality of life instrument specific to ankylosing spondylitis

Background: Although disease-specific health status measures are available for ankylosing spondylitis (AS), no instrument exists for assessing quality of life (QoL) in the condition. Objective: To produce an AS-specific QoL measure that would be relevant and acceptable to respondents, valid, and reliable. Methods: The ASQoL employs the needs-based model of QoL and was developed in parallel in the UK and the Netherlands (NL). Content was derived from interviews with patients in each country. Face and content validity were assessed through patient field test interviews (UK and NL). A postal survey in the UK produced a more efficient version of the ASQoL, which was tested for scaling properties, reliability, internal consistency, and validity in a further postal survey in each country. Results: A 41 item questionnaire was derived from interview transcripts. Field testing interviews confirmed acceptability. Rasch analysis of data from the first survey (n=121) produced a 26 item questionnaire. Rasch analysis of data from the second survey (UK: n=164; NL: n=154) showed some item misfit, but showed that items formed a hierarchical order and were stable over time. Problematic items were removed giving an 18 item scale. Both language versions had excellent internal consistency (α=0.89–0.91), test-retest reliability (r(s)=0.92 UK and r(s)=0.91 NL), and validity. Conclusions: The ASQoL provides a valuable tool for assessing the impact of interventions for AS and for evaluating models of service delivery. It is well accepted by patients, taking about four minutes to complete, and has excellent scaling and psychometric properties

The international development of the RGHQoL: a quality of life measure for recurrent genital herpes.

This paper describes the international development and psychometric testing of the Recurrent Genital Herpes Quality of Life Questionnaire (RGHQoL), a condition-specific quality of life (QoL) instrument. The theoretical foundation for the measure is the needs-based model of QoL and the content of the instrument was derived from in-depth qualitative interviews with relevant patients in the UK. Versions of the RGHQoL were required for the UK, USA, Italy, Germany, France and Denmark for use in international clinical trials. The results indicate that the final 20 item measure has good reliability, internal consistency and validity for all language versions. A small responsiveness study in Denmark suggested that the measure is sensitive to changes in QoL associated with the initiation of suppression treatment for recurrent genital herpes (RGH). It is concluded that the RGHQoL is a valuable instrument for inclusion in clinical trials. The psychometric properties of the instrument are such that it may also be used to monitor the progress of individual patients

Development of the PSORIQoL, a psoriasis-specific measure of quality of life designed for use in clinical practice and trials

Background: Patients with psoriasis have significant impairment in their quality of life (QoL). Several patient-completed instruments are available to measure outcome in dermatological conditions but these primarily focus on severity of disease rather than on QoL. Objectives: To develop a new instrument specifically designed to measure QoL in psoriasis—the Psoriasis Index of Quality of Life (PSORIQoL). Methods: The content of the instrument was derived from qualitative interviews with 62 psoriasis patients in the U.K., Italy and the Netherlands. Content analysis of the interview transcripts from the three countries identified potential items for the questionnaire. All further stages of the project were conducted in the U.K. only. Face and content validity were determined by means of a focus group held with seven psoriasis patients and face-to-face interviews with a further 21 patients. A new draft version of the PSORIQoL, together with the Dermatology Life Quality Index (DLQI) and the General Well-Being Index (GWBI), were completed by a new sample of psoriasis patients contacted by mail, in order to determine construct validity. A subsample of the respondents completed a similar package 2 weeks later, to assess reproducibility (reliability). Results: The first version of the PSORIQoL consisted of 61 items covering the needs identified in the interviews as having been affected by psoriasis or its treatment. These included fear of negative reactions from others, self-consciousness and poor self-confidence, problems with socialization, physical contact and intimacy, limitations on personal freedom and impaired relaxation, sleep and emotional stability. Following the focus group and field-test interviews, a new draft measure consisting of 45 items was completed by 148 patients, 88 of whom completed and returned a similar package 2 weeks later. Application of Rasch analysis identified a final 25-item version of the PSORIQoL. This version had a test–retest reliability coefficient of 0·89, indicating good reproducibility. The levels of association with the DLQI and PGWB indicated that the PSORIQoL measures a related but distinct construct. Conclusions: The PSORIQoL appears to be a practical, reliable and valid instrument for measuring the impact of psoriasis on QoL. It remains necessary to establish the instrument's responsiveness to changes in QoL associated with treatment