P70 Evaluating the WASTEd: a new co-produced patient-reported measure of axial spondyloarthritis (axSpA) fatigue and energy
Authors: Pearson Nathan A , Parsons Helen , Tutton Elizabeth , Martindale Jane , Strickland George , Thompson Jean , Packham Jonathan , Haywood Kirstie L 
Published: April 2020

Abstract

Background
Fatigue in axSpA is described as a complex, multidimensional symptom that involve disease-specific, cognitive/behavioural and personal factors. However, current assessment guidance in axSpA recommends using a single-item visual analogue scale on fatigue severity. This type of provides a limited assessment and may fail to adequately capture the multiplicity of fatigue experience. Despite the high prevalence and significant impact of fatigue, there is currently no axSpA-specific patient-derived multi-item questionnaire for fatigue. In our previous qualitative research, we identified energy as a related but distinct component of fatigue experience in axSpA. In response, and in collaboration with our patient and public involvement (PPI) group, we have co-produced a 30-item patient-reported outcome measure (PROM) specific to axSpA-fatigue and energy: the Warwick Axial Spondyloarthritis faTigue and Energy measure (WASTEd). The aim of this study was to evaluate the quality of the WASTEd and make statistically informed item refinement decisions following completion by a UK-wide patient cohort.

Methods
A UK-based postal survey of 580 axSpA patients provided necessary data supporting both classic (Classic Test Theory; CTT) and modern (Rasch Measurement Theory; RMT) psychometric evaluation. CTT analysis included evaluating structural validity using exploratory factor analysis (EFA), internal consistency using Cronbach’s alpha and assessing item-total correlations. RMT analysis included evaluating evidence of local dependency between items, item fit and category characteristic curves.

Results
The survey response rate was 64.13% (n = 372). EFA identified four factors: energy, fatigue, symptoms and control. Five items were removed due to narrow cross-loadings. Final item-total correlations ranged from 0.61 to 0.83. Cronbach’s alpha was estimated to be 0.97. Rasch analysis highlighted one item as under discriminating. Numerous items showed evidence of respondents opting for a middle-option answer following visual inspection of the category characteristic curves. Findings were discussed with the study PRP group and co-refinement (item removal, modification or introduction) decisions were made during the meeting. A further seven items were removed to produce a final 18-item short-form version of the WASTEd.

Conclusion
The WASTEd has good evidence of data quality, structural validity and content validity. Psychometric evidence supports qualitative findings that energy is a distinct but related component in fatigue experience. Following a final stage of testing, the WASTEd will be ready for incorporation into both research and clinical practice settings, providing an essential patient-derived assessment of fatigue and energy with which to inform shared decision-making.

Disclosures
N.A. Pearson None. H. Parsons None. E. Tutton None. J. Martindale Honoraria; JM has received speaker fees and/or honoraia from Abbvie Ltd, Novartis, Pfizer and UCB. Grants/research support; JM has received a research grant from Pfizer. G. Strickland None. J. Thompson None. J. Packham None. K.L. Haywood None.