Factor Structure and Convergent Validity of the Derriford Appearance Scale-24 Using Standard Scoring Versus Treating “Not Applicable” Responses As Missing Data: A Scleroderma Patient-Centered Intervention Network Cohort Study

Erin L. Merz¹, Linda Kwakkenbos^2,3,4, Marie-Eve Carrier², Shadi Gholizadeh⁵, Sarah D. Mills⁶, Rina S. Fox⁷, Lisa Jewett^2,8, Heidi Williamson⁹, Diana Harcourt⁹, Shervin Assassi¹⁰, Daniel E. Furst¹¹, Karen Gottesman¹², Maureen D Mayes¹³, Tim Moss⁹, Brett D. Thombs^2,3 and Vanessa L. Malcarne^6,14, ¹Department of Psychology, California State University, Dominguez Hills, Carson, CA, ²McGill University, Montreal, QC, Canada, ³Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, QC, Canada, ⁴Radboud University, Nijmegen, Netherlands, ⁵Psychoogy, SDSU/UC San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, ⁶SDSU/UC San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, ⁷Northwestern University Feinberg School of Medicine, Chicago, IL, ⁸Jewish General Hospital, Montreal, QC, Canada, ⁹University of the West of England, Bristol, United Kingdom, ¹⁰University of Texas McGovern Medical School, Houston, TX, ¹¹Department of Internal Medicine and Rheumarology, University of California Los Angeles, David Geffen School of Medicine, Division of Rheumatology; University of Washington, Seattlr, Washington; University of Florence, Florence, Italy, Los Angeles, CA, ¹²Scleroderma Foundation, Los Angeles, CA, ¹³Department of Internal Medicine - Rheumatology, University of Texas-McGovern Medical School, Houston, TX, ¹⁴Psychology, San Diego State University, San Diego, CA

Meeting: 2017 ACR/ARHP Annual Meeting

Date of first publication: September 18, 2017

Keywords: Systemic sclerosis

Session Information

Date: Tuesday, November 7, 2017

Session Title: ARHP Measures and Measurement of Healthcare Quality Poster

Session Type: ACR Poster Session C

Session Time: 9:00AM-11:00AM

Background/Purpose: Valid measures of appearance concern are needed in systemic sclerosis, a rare, disfiguring rheumatologic disease. The Derriford Appearance Scale-24 (DAS-24) is a self-report measure that assesses appearance-related distress related to visible differences. There is uncertainty regarding the DAS-24 factor structure, possibly due to its scoring method of the 14 items with a “not applicable” response option.

Methods: Patients with systemic sclerosis (N = 950) completed self-report measures at enrollment to the Scleroderma Patient-centered Intervention Network (SPIN) Cohort Study. DAS-24 items marked “not applicable” were scored two ways: (1) “not applicable” scored as 0, per standard DAS-24 scoring; (2) “not applicable” treated as missing. Internal consistency reliability was evaluated using Cronbach’s alpha. The one-factor DAS-24 model was evaluated using confirmatory factor analysis. Convergent validity was evaluated using bivariate correlations with social interaction anxiety, depressive symptomatology, fear of negative evaluation, and satisfaction with appearance.

Results: Internal consistency reliability was high (α = .92). When items marked by respondents as “not applicable” were scored as 0, the one-factor model fit poorly (CFI = .896, RMSEA = .096). When items marked by respondents as “not applicable” were treated as missing data, the one-factor model fit well (CFI = .958, RMSEA = .065). Convergent validity analyses revealed strong correlations that were similar across scoring methods (Standard rs: .44-.68; Missing rs: .47-.72).

Conclusion: Treating “not applicable” responses as missing improved the measurement model, but did not yield substantively different relationships with theoretically related constructs. It is unlikely that using standard DAS-24 scoring greatly impacts the practical interpretation of scores. Indications of item redundancy and poorly performing items suggest that the DAS-24 could be improved and potentially shortened.

Disclosure: E. L. Merz, None; L. Kwakkenbos, None; M. E. Carrier, None; S. Gholizadeh, None; S. D. Mills, None; R. S. Fox, None; L. Jewett, None; H. Williamson, None; D. Harcourt, None; S. Assassi, None; D. E. Furst, None; K. Gottesman, None; M. D. Mayes, None; T. Moss, Derriford Appearance Scale, 4; B. D. Thombs, None; V. L. Malcarne, None.

To cite this abstract in AMA style:

Merz EL, Kwakkenbos L, Carrier ME, Gholizadeh S, Mills SD, Fox RS, Jewett L, Williamson H, Harcourt D, Assassi S, Furst DE, Gottesman K, Mayes MD, Moss T, Thombs BD, Malcarne VL. Factor Structure and Convergent Validity of the Derriford Appearance Scale-24 Using Standard Scoring Versus Treating “Not Applicable” Responses As Missing Data: A Scleroderma Patient-Centered Intervention Network Cohort Study [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/factor-structure-and-convergent-validity-of-the-derriford-appearance-scale-24-using-standard-scoring-versus-treating-not-applicable-responses-as-missing-data-a-scleroderma-patient-c/. Accessed September 24, 2021.

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