Development and validation of a patient-reported outcome instrument for skin involvement in patients with systemic sclerosis.

OBJECTIVES: We developed a patient-reported outcome (PRO) instrument to assess the skin-related quality of life in patients with systemic sclerosis (SSc). METHODS: Participants with SSc provided input on skin-related health effects through focus groups. We developed items for scleroderma skin PRO (SSPRO) to encompass these effects. Further consideration from cognitive interviews and an expert panel led to reduction and modification of items. A 22-item SSPRO was field tested. Psychometric analysis included test-retest reliability, internal consistency and exploratory factor analysis (EFA). Construct validity was assessed through correlation with other participant and physician-assessed measures. RESULTS: 140 participants completed the SSPRO: mean age was 53.4 years, median disease duration was 5 years, 82.1% were female and 32.9% had diffuse cutaneous SSc. EFA supported four factors in SSPRO corresponding to hypothesised constructs: physical effects, physical limitations, emotional effects and social effects. Removal of 4/22 items resulted in acceptable goodness-of-fit statistics. Test-retest reliability (intraclass correlation coefficient=0.61-0.83) was moderate to high and internal consistency (Cronbach's α=0.89-0.96) was high. SSPRO correlated strongly with other participant-reported measures (r=0.59-0.88) suggesting construct validity, and less well with physician-assessed measures (r=0.31-0.40). SSPRO scores were significantly different for each level of participant-reported skin severity, and for limited versus diffuse cutaneous SSc. CONCLUSIONS: SSPRO has been developed with extensive patient input and demonstrates evidence for reliability and validity. It is complementary to existing measures of SSc skin involvement with emphasis on the patient's experience. Further research is needed to assess its sensitivity to change.

Expression of Generalized Anxiety Disorder Across the Lifespan.

In generalized anxiety disorder (GAD), both the associated symptoms and worry content have been shown to vary as a function of age (Jeste et al., 2005; Portman et al., 2011). However, few studies have conducted analyses beyond mean comparisons and no studies have examined whether the observed differences in worry content and the associated symptoms are due to the lack of measurement invariance across age groups. The current study evaluated whether the measurement and expression of GAD in adults varied as a function of age, using a clinical sample of 375 participants and dimensional measures of GAD. The sample was divided into three age groups (OLDER = 60+, MID = 40-59, YOUNG = 20-39), matched by sex and GAD status. Two associated symptoms were found to exhibit differential item functioning, overall distress/interference as well as fatigue, with higher levels distress/interference and lower levels of fatigue found in the OLDER age group despite equivalent GAD severity levels across groups. When examining the content of reported worries, differential item functioning was found in four worry domains. Holding the latent dimension of worry severity constant: (a) the YOUNG age group was found to have higher reported rate of social worries, and (b) the OLDER age group was found to have higher levels of reported worries about community/world affairs and health of self. The OLDER age group also exhibited lower levels of worry about work and school. These results are discussed with regard to the assessment of GAD across the lifespan.