The GSCI Principal Investigator (SH) and Scientific Secretaries (MN, RC, PC, EH) invited internationally recognized, interprofessional authors, policy and opinion leaders, scientists, and clinicians with expertise and interest in spinal disorders to participate in the GSCI classification development process. After the initial list of invitees was developed, the experts were asked for additional participant recommendations. During this initial process, GSCI Principal Investigators focused on including representatives from a broad range of disciplines and nations. Criteria for the classification system were developed to meet the mission of the GSCI (see Online Resource Figure 1 for criteria for the development of the classification system for spine-related concerns).
Review of spine classification systems
A search of the literature was performed and input from the members of the GSCI was collected to identify classification systems that could meet the criteria for the development of the care pathway and implementable model of care. The literature search revealed many papers classifying the severity of specific spine pathologies such as vertebral body fractures, scoliosis, disk herniation or degeneration but failed to identify classification systems that would apply more generally to people with spine-related symptoms or concerns. Members of the GSCI then identified 10 extant spinal disorders classification systems that were widely used or proposed for clinical guideline or research considerations and that addressed people presenting with spine-related symptoms (Table 1) [7,8,9,10,11,12,13,14,15,16,17].
One of the most widely used classification systems to differentiate spinal disorders by clinicians and payers in high-resource countries is the International Classification of Diseases (ICD) developed by World Health Organization (WHO) . The ICD-10 lists over 300 diagnostic codes which could apply to people who present with spinal symptoms or diagnoses. The use of the ICD requires a specific, often pathological diagnosis. Most of the ICD codes focus on an exclusive biomedical approach to spinal disorders . This classification, although helpful in tracking diagnoses, does not apply well to implementation in a care pathway since they include over 300 diagnostic codes and do not take into account psychosocial factors.
The International Classification of Functioning, Disability and Health (ICF) also developed by the WHO focuses on function . The ICF describes function as “an umbrella term for body functions, body structures, activities and participation.”  The ICF is a general description of function that, if used in isolation, does not discuss a pathological diagnosis or intervention. To achieve this goal, it should be linked to ICD codes. The ICF and ICD are important in defining diagnoses and disability. However, these classification systems are complex, detailed and are difficult to use outside of a comprehensive high-resource health care setting with extensive administrative resources.
Several task forces have been convened to address spine conditions or symptoms, review the evidence for interventions, and make classification recommendations. The Quebec Task Force on Whiplash-Associated Disorders divided neck pain into five groups . This classification, however, only addressed whiplash injuries to the neck, mostly from motor vehicle crashes. The Quebec Task Force on Spinal Disorders recommended differentiating spine-related disorders into groups based on symptoms, clinical, and neurological findings . It focuses on symptoms and pathology and requires the user to differentiate 11 classes, which mostly relate to pathology. The Bone and Joint Decade Task Force on Neck Pain and Its Associated Disorders used the Quebec Whiplash Classification system as a foundation and defined groups based on activity interference due to neck pain and the presence or absence of radiculopathy . Serious pathology was defined as group IV in this classification, and conditions in this group were not addressed further. The National Institute of Health Back Pain Standards (NIHBPS) mirrors the criteria of the Neck Pain Task Force (NPTF) focusing on symptoms and disability for low back pain but, in addition, differentiated classes based on chronicity and severity of impact or impairment . The NPTF and NIHBPS classification systems have been valuable in the discussion of the evidence for effectiveness of interventions and have led to more reasonable and logical approaches to patients, especially those with incapacitating low back and neck pain. These efforts have resulted in a greater focus on interventions that are supported by available evidence. They have stressed the importance of psychosocial factors and the reduction of the use of interventions with little supporting evidence. However, they address a limited number of symptoms such as low back, neck pain, or whiplash-associated symptoms. Therefore, they are not suitable for use in a setting that applies to people with spine symptoms or concerns irrespective of the nature of the symptom, spine region, severity, chronicity, and potential pathologies that a general spine care pathway needs to address.
Work-related disabilities were addressed in several classifications. The South Australia Work Cover Corporation Classification System was developed to determine legal impairment and focuses primarily on differentiating patients with non-specific pain from those with a pathological diagnosis . The AMA Guide to the Evaluation of Permanent Impairment, 5th edition is widely used in the USA as a means of establishing compensation for spine-related disability . This system is based on clinical findings (e.g., muscle spasm or range of motion), the presence of radiculopathy, and loss of structural integrity. The 6th edition of the AMA Guides has similar goals but focuses on symptoms and impairment of activities caused by the symptoms . These classification systems are used to determine legal impairment and should only be applied when a patient reaches the point of maximum medical improvement and therefore do not apply to people who are seeking care.
After deliberation, the panelists felt that any classification system should be compatible with survey instruments such as those developed by the Global Alliance for Musculoskeletal Health, so it would be relatively easy to translate the results of surveys into the implementation of a care pathway . The classification panel recognized that none of the available and widely used classification systems presented above can guide clinicians to care for people who present with all possible forms of spine symptoms, concerns, or pathologies. It became evident that the panel needed to develop a comprehensive classification system to address all spine care concerns before a care pathway could be considered. The classification must include any person who might present to a spine program. The panel recognized that in some low-resource communities there may be presentations other than primary neck or low back pain, which may not be adequately addressed in the classic evidence-based guidelines that were established in high-income settings. In many global spine care programs, people may have concerns about minor irritating symptoms, prevention, and risk factors, but also pain that is in multiple spine regions, neurological symptoms and deformities, in addition to serious systemic pathology. Thus, the classification system must be created to address all presentations.
Several meetings were held to refine the classification system. An initial draft that incorporated applicable principles of existing classification systems was presented to the GSCI workgroup. The participants wanted the classification to be compatible with other spine classification systems, relatively simple to use, and applicable to first-contact, health care specialties or professions. Refinements of the document were made through 4 round-table group discussions and multiple meetings among the executive and members of the classification panel. This process yielded an initial seed classification system (see Online Resource Figure 2).
Modified Delphi process
A modified Delphi process was performed to gain further input on the classification system and to obtain consensus from an interprofessional, international panel of spine care clinicians, researchers, and other stakeholders [21,22,23]. The modified Delphi process was selected because it allowed all participants to have an equal voice in the discussion and reduced the potential for bias or intimidation by senior researchers [21,22,23]. Throughout the process, comments were blinded so that the participants’ identities were not tied to comments when being reviewed by the principal investigators (SH, CJ). Comments were opened by the principal investigators only after all participants had responded. The participants gave informed consent that the GSCI research papers would be published with information including participant names, information from surveys/emails, and relevant conflict of interest information for purposes of transparency. Participants were given the right to refuse or withdraw without penalty at any time. This project was approved by National University of Health Sciences Institutional Review Board (#H-1503). All participants were informed about the nature of the study and the modified Delphi process and gave written consent by completing the electronic questionnaire. Surveys were distributed using an online survey program (SurveyMonkey Inc, SurveyMonkey.com, San Mateo, California, USA).
The seed document was provided as the starting document. The first Delphi survey asked participants for their level of agreement on the overall classification, on each individual class, and gave the respondent the opportunity to provide comments. The first survey also included questions about demographics and their views and beliefs about health care. The first Delphi survey responses were collected and were matched to the relevant class. Each comment was considered and addressed by the GSCI Principal Investigators (SH, CJ) and the Executive Team (RC, PC, EH, MN) in a response report, which included recommended changes in the initial proposal with explanations and clarifications to address comments and concerns. Examples of patient presentations for each class were provided to clarify use of the classification (see supplemental file Appendix A).
All 43 participants from the first survey were invited to participate in the second round and were given the full response report in advance. The second Delphi survey asked participants to state their overall agreement, agreement with minor changes, or disagreement with the updated draft and to include any comments about the updated classification system. Consensus for the second survey was defined a priori as 80% agreement. The responses and comments were collected from the second survey. Since there was high agreement (95% of participants supported the updated classification), a third survey was not undertaken. Based upon feedback from the second survey, minor changes were made to the classification system, which included corrections to grammar and congruence. Following this, all participants were asked to review the manuscript draft, provide additional input, and invited to join as coauthors. (see Online Resource Figure 3 for the steps in the consensus process.)