Professional identity is a multifaceted concept that transcends mere affiliation with a particular profession and involve a complex interplay of individual beliefs and perceptions [1]. Chiropractic, defined by the World Health Organisation [2] as “a health care profession concerned with the diagnosis, treatment and prevention of disorders of the neuromusculoskeletal system and the effects of these disorders on general health; there is emphasis of manual techniques used such as joint adjustments and/or manipulation, with particular focus on subluxations” (p3), faces an ongoing lack of clarity surrounding its role within the broader healthcare landscape [3,4]. Disagreement persists on what characterises the chiropractic profession, its philosophy, and scope of practice [[5], [6], [7]]. The identity crisis extends beyond external perceptions, impacting chiropractors themselves, who grapple with the unclear public identity of the profession due to contrasting practice styles [8,9]. Despite commentary from chiropractic researchers and academics on the profession's ongoing struggle to define its identity [[10], [11], [12], [13], [14], [15]], attempts to bridge divergent approaches have been met with contention [7,16], and remain unresolved [17,18]. Debate continues to revolve around categorisation of chiropractic professionals into subtypes relating to philosophical and therapeutic orientations in patient care [[19], [20], [21], [22], [23], [24]]. Recent research by Glucina et al. [25] revealed that practitioner subtypes alone may oversimplify the rich concept of chiropractic professional identity (CPI). Exploring the field of professional identity across numerous disciplines through a concept analysis, six overarching domains were found to constitute CPI [1]: knowledge of professional ethics and practice standards [2], chiropractic history [3], practice philosophy and motivation [4], chiropractor roles and expertise [5], professional pride and attitude, and [6] professional engagement and interaction behaviours. This multi-dimensional framework serves as the foundation for this study.

Chiropractic professional identity has been defined by Glucina et al. [25] as "a chiropractor's self-perception and ownership of their practice philosophies, roles and functions, and their pride, engagement, and knowledge of their profession" (p80). In this context, it is crucial to recognise the enduring schism between Vertebral Subluxation (VS) and Musculoskeletal (MSK) treatment-focused chiropractors, a division with deep-rooted conceptual differences, potentially hindering the profession's advancement [26]. Broadly, chiropractors impact the neuromusculoskeletal system, while the focus of VS chiropractors centres on evaluating and addressing biomechanical derangements of the spine, which are assumed to be caused by bodily stressors, producing clinically significant maladaptive effects on neurological function and sensorimotor integration [27,28]. In contrast, MSK treatment-focused chiropractors prioritise improving dysfunctional joints through mobilisation to alleviate pain [15]. A third, “centrist”, group of chiropractors incorporates elements of the traditional VS-focused chiropractic philosophy, while concurrently addressing general MSK complaints [29,30].Research examining chiropractic practice orientation subtypes has employed diverse methodologies. Some studies [20,31] applied subtype categorisations proposed by McGregor et al. [22]. In this Canadian study, the majority (81.2%) of chiropractors belonged to the orthodox, mainstream MSK evidence-based category, while the remaining 18.8% were classified as unorthodox or traditional VS-based chiropractors [22]. Using these categorisations, a European study reported that 79.9% of chiropractors were orthodox, leaving 20.1% in the unorthodox category [31]. In the United States, Gliedt et al. [20] adapted the McGregor et al. [22] framework, creating three mutually exclusive chiropractic subgroups, with results indicating that 21.2% identified as VS-focused, 56.8% as spine/neuromusculoskeletal focused, and 22% as a "healthy life doctor" or general primary care-focused chiropractic subgroup. Chiropractic students' perspectives on subtypes and categorisations have shown significant variability, often quantified through percentages reflecting agreement with specific attitude statements [24,[32], [33], [34]]. Practice orientation subtypes contribute to discord within the profession, potentially hindering its unity [4,7]. Chiropractors adhering to traditional VS beliefs may pose barriers to the legitimisation of chiropractic within wider healthcare [20]. The prevailing narrative within chiropractic academia advocates an evidence-based approach, emphasising the management of MSK disorders for a limited range of conditions, as championed by the MSK-focused proponents [15,35]. The MSK approach is credited by some with making the profession more accountable, scientifically based, and grounded in academic research to improve clinical service efficacy and safety [15,36]. In contrast, VS chiropractors, according to proponents of the MSK-focused approach, do not align with evidence-based practices and could impede mainstream chiropractic progress [37]. Nevertheless, scientific research conducted by chiropractors investigating VS in basic and clinical science is largely overlooked by MSK-focused advocates [21].

Professional identity instruments have been developed in various health-related disciplines such as nursing [e.g. Nurses Self-Concept Questionnaire [38]], counselling [e.g. Professional Identity Scale in Counselling [39]], physicians [e.g. Development Scale [40]] and healthcare workers [e.g. Professional Identity Scale for Healthcare Students and Professionals [41]]. However, within chiropractic, while research has explored attitudes related to CPI, there is currently no tool available that specifically assesses CPI across its multiple domains. This represents a significant gap in the profession, as essential questions about chiropractors’ professional identity and their expected behaviours remain unanswered. Developing an instrument to measure CPI could help chiropractors clarify their role and distinguish themselves from other related professions. Furthermore, it could shed light on areas where the chiropractic profession could enhance and strengthen its professional identity, potentially leading to increased self-esteem, job satisfaction, and success [1,42,43]. Notably a strong professional identity is crucial, as a poor identity within chiropractic, has been linked to burnout and professional dissatisfaction [44].

The objective of this current research is to develop a concise psychometrically robust instrument capable of capturing the fundamental elements shared across all chiropractic practice approaches while operationalising the CPI construct. The significance of this study becomes evident in several key areas: Firstly, clinicians can significantly benefit from this tool as it empowers them to assess their own CPI, potentially leading to enhanced career satisfaction and personal growth. Secondly, patients also stand to gain from this research as the CPIES can be applied to explore correlations with patient health outcomes, providing insights into the effectiveness and significance of diverse aspects of chiropractic care. Additionally, the instrument can be employed to assess the development of professional identity over time, contributing to deeper understanding of the evolving nature of CPI. Lastly, chiropractic organisations and institutions can use the CPIES to evaluate their collective or individual CPI, aligning their practices more closely with their values and objectives.