A core outcome measurement set for whiplash associated disorders—Editorial

The global disability burden of musculoskeletal pain conditions has been well documented in recent years [1]. Whiplash Associated Disorder (WAD) is a common musculoskeletal condition, traumatic in onset usually from a road traffic crash, that incurs substantial costs related to treatment of physical and mental health as well as lost productivity [2]. Whilst the cardinal symptom of WAD is neck pain, the condition appears to be more complex than neck pain of nontraumatic onset, at least for some individuals. For example, people with WAD report higher pain, disability [3] and distress [4], greater cognitive problems [5], and more marked features of nociplastic pain including greater pain sensitivity [6] and loss of endogenous modulation [5]. The Global Burden of Disease initiative does not differentiate traumatic and non-traumatic musculoskeletal pain, but it is likely that WAD contributes significantly to global disability burden. Progress in improving health outcomes after whiplash injury has been slow. The majority of treatments including physical and psychological approaches have mostly small effects on pain and disability [7,8]. Inconsistency and heterogeneity in the use of patient-reported outcome measures in clinical trials of treatments for WAD has hampered comparisons between clinical trials and limited capacity for data pooling in systematic reviews [9,10]. To address this problem, in 2017, we established an International Steering Committee that aimed to develop a Core Outcome Set (COS) for clinical trials of interventions for patients with WAD (the CATWAD initiative). The committee adhered to the recommendations of the Core Outcome Measures in Effectiveness Trials (COMETs), the protocol was registered in the COMET database and published in detail [11]. The first step in the process of COS development is to agree upon core outcome domains that should be measured. Through a 3-stage Delphi consensus process with stakeholder groups including clinical researchers, clinicians, patients and insurance personnel, six core domains were recommended: Physical Functioning, Perceived Recovery, Work and Social Functioning, Psychological Functioning, Quality of Life and Pain [12]. Following this process, systematic reviews were conducted for each core domain to identify potential core outcome instruments and evaluate their measurement properties, feasibility, and ease of use. In terms of identifying core outcome instruments shown to have sound psychometric properties in WAD, the results of the systematic reviews were disappointing. Numerous PROMS were identified covering the six core domains, but none had undergone evaluation of content validity in patients with WAD, although some had moderate to high quality evidence for sufficient internal structure. The reviews found that PROMs for pain and disability had undergone more extensive evaluation than some of the other domains [13,14]. In particular, psychological PROMs were not well evaluated in patients with WAD [15], concerning for a condition where psychological factors have been shown to be an important factor associated with health outcomes. Based on these results, the International Steering Committee reached 100% consensus to recommend the following COS: Neck Disability Index and Whiplash Disability Questionnaire (Physical Functioning), Global Rating of Change Scale (Perceived Recovery), one of five PROMS [PFACTS-C, Pain Self Efficacy Questionnaire, Pain Catastrophizing Scale, Harvard Trauma Questionnaire, and the Posttraumatic Stress Diagnostic Scale] (Psychological Functioning), EQ-5D-5L of SF-6D (Quality of Life), Numeric Pain Rating Scale and Visual Analogue Scale (Pain) and single item questions and SF-6D (Work and Social Functioning). With respect to psychological PROMs, it is suggested that one of the five be selected based on the nature of the intervention being tested. For example, if the intervention is targeting fear of movement, then the PFACTS-C could be used. There is clear need for further evaluation of measurement properties of some of the recommended PROMs in patients with WAD. As this occurs with time, the CATWAD recommendations will be updated. Nevertheless, a core outcome measurement set for WAD is available for use and agreed by an international and multidisciplinary group of researchers, clinicians, and patients. The use of core sets has been shown to improve outcome standardisation in clinical trials [16] and can greatly benefit future evidence syntheses for patients with WAD.