Development of the AOSpine Patient Reported Outcome Spine Trauma (AOSpine PROST): a universal disease-specific outcome instrument for individuals with traumatic spinal column injury

The AOSpine Knowledge Forum Trauma initiated a project to develop universal disease-specific outcome instruments for spine trauma patients. Because of the possible discrepancies when comparing outcomes from the patients’ perspective to clinical and radiological assessments by the clinicians, two separate tools were developed: the Patient Reported Outcome Spine Trauma (AOSpine PROST) to represent the patients’ perspective, and the Clinician Reported Outcome Spine Trauma (AOSpine CROST) to cover the perspective of the treating surgeons [1].

Although a number of outcome measures have been used in individuals with traumatic spine injuries, these tend to focus on the impact of paralysis [2]. In the absence of an instrument that is specifically designed and validated for spine trauma patients without complete paralysis, it is difficult to compare outcomes of different treatments of the spinal column injury within and between studies [3]. Because of the persisting controversies on the optimal treatment of many types of these injuries, there is a real need for such an instrument [4‐6].

The systematic approach and methodology of the International Classification of Functioning, Disability, and Health (ICF) of the World Health Organization (WHO) was used as the basis for the development of the AOSpine PROST [7, 8]. The ICF recognizes that functioning and disability are multi-dimensional concepts relating to different components: body functions (b), body structures (s), activities and participation (d), and environmental factors (e). Figure 1 shows the components of the ICF and the hierarchical organization of more than 1400 categories into different levels of detail. This article reports on the multi-phase process used in developing the AOSpine PROST, as well as the results of its application in a pilot study.

Four different studies were completed in the preparatory phase of the project, all of which have been published. Three preparatory studies aimed to identify ICF categories relevant to measure the outcomes of traumatic spinal column injuries from different perspectives. The research perspective was covered by a systematic literature review [3]. Out of 5117 screened references, 245 were included, and 17 different frequently used outcome measures used in spine trauma research were identified. The content of these measures were linked to 57 ICF categories, using established linking rules [9, 10]. The expert perspective was explored through a web-based survey among 150 experienced spine trauma surgeons from all world regions, and identified 13 ICF categories as most relevant [11]. The patient perspective was investigated in an international empirical study including 187 patients from nine trauma centers in seven countries, and yielded 38 ICF categories as the most important [12]. A fourth study investigated various question and response formats for their potential use in the patient reported outcome instrument [13].

In the next phase, a formal consensus process integrated evidence from the preparatory studies and expert opinion [14].

From a pool of candidates already involved or interested in the project, eleven international spine trauma experts from six countries were selected to attend a consensus conference. The selected experts are globally renowned for their contributions that have advanced the field of spine trauma research and care. Based on voting and group discussions, 25 out of 159 relevant ICF categories were selected as core categories (Table 1). A core ICF category was defined as being (a) relevant for adult traumatic spinal column injury patients, (b) relevant for clinical and functional recovery during the acute and post-acute time frame, and (c) meaningful to include in the outcome instrument. The attendants also agreed on one specific question format as well as the 0–100 Numeric Rating Scale (NRS-101) as the response format to use as the scale (Fig. 2).

Using the systematic approach and methodology of the ICF, and based on the results of four different preparatory studies and an international consensus conference, a disease-specific patient reported outcome instrument for traumatic spinal column injury patients has been developed. A Dutch draft version of this 19-item AOSpine PROST was pilot tested and showed very satisfactory results for comprehensibility, relevance, acceptability, feasibility, and completeness, as well as high internal consistency.

The ICF methodology as well the ‘think aloud’ and ‘probing’ methods have proven to be very good and valid methodologies for developing and refining outcome instruments [7, 8, 15, 17‐19].

The 19 items of AOSpine PROST cover a wide range of domains, including and beyond the scope of activities of daily living. With the specific response scale, patients are able to compare their current level of function with their situation before the trauma. This makes the AOSpine PROST valuable compared to outcome measures that solely focus on the level of dependence in patients’ daily activities, such as the SCIM and WISCI [20, 21]. Applying these outcome instruments to patients with only mild or transient neurological deficits would result in ceiling effects. Moreover, the AOSpine PROST includes many items that could be very relevant for spinal cord injured patients, e.g. ‘Urination’, ‘Defecation’, and ‘Changing your body position’. In contrast to many other outcome measures used in this specific patient population, which include generic outcome measures and instruments designed for patient populations with degenerative conditions [3], the AOSpine PROST holds promise as a useful outcome measure in patients with and without neurological deficit, making it more feasible for clinical use as well.

All 25 core ICF categories could be incorporated in the AOSpine PROST, except for Products or substances for personal consumption (e110). This ICF category was defined as a core category, with the rationale of possibly including a separate item that would describe the use of opioids. During the pilot study, two patients indicated that opioid use is a missing item and should be included. However, the overall concept of the outcome instrument relates more to the functional impairment and the problems in daily living related to this impairment and not to specific treatment strategies such as the use of medication. Opioid use could be taken into account for the AOSpine CROST, the future outcome instrument from the perspective of the treating surgeons [22, 23].

The findings obtained from the pilot study are of great value for refining the AOSpine PROST prior to multicenter validation of this instrument. In the next phase, the items ‘Work/Study’ and ‘Energy level and motivation’ will be adjusted because of the difficulties experienced by the patients when answering these questions. Examples will be added to the ‘Work/Study’ item, and the motivation part will be removed from the item ‘Energy level and motivation’ as ceiling effects could be expected for ‘Motivation’ when separating it as an item. Another valuable finding was that patients scored their level of function by taking all provided examples into account and calculate an average score. This may lead to lower item-total correlations for the specific items. To abolish this obscurity, instructions will be added to base the score on the situation or example where the patient is most disabled.

We do recognize several limitations of the development process for this outcome instrument. First, this process slightly deviates from the ICF Core Set development guideline, e.g. a focus group was not included in the preparatory phase [7]. Nevertheless, the chosen process provides a solid and systematic base for the selection of the core ICF categories described in this article. Second, a specific trauma patient population was chosen. The rational was to exclude confounding factors and focus on the effect of spinal column injury on health and function in the acute and post-acute phase. Once validated in this specific patient population, the AOSpine PROST will be subjected to further validation in completely paralyzed patients as well. Third, the number of patients included in the pilot study could be debated. We believe this is a sufficient number to explore the most common obstacles experienced by the patients to fill out the AOSpine PROST. Fourth, analyses as test–retest reliability, floor and ceiling effect, or responsiveness were not performed in the pilot study. These analyses will be performed in the next phase in a multicenter validation study including a considerable larger number of patients. Finally, in the development process the Dutch version was freely translated into English to be reviewed by the AOSpine Knowledge Forum Trauma. We believe this is acceptable for this phase of the project. Once a definitive Dutch version is developed and ready to be validated, a careful translation into English will be performed and the linguistic equivalence of both versions will be checked using established guidelines [24].

In conclusion, using the ICF methodology and incorporating the results of four preparatory studies and an international consensus conference, the AOSpine Patient Reported Outcome Spine Trauma (AOSpine PROST) was developed. Taking the results from the subsequent pilot study into account, a definite version will be developed, followed by international multicenter studies to validate both the Dutch and English versions. Once validated, the AOSpine PROST together with the AOSpine CROST have the potential to be useful in the clinics as well as research, to evaluate, compare and establish the effectiveness of interventions in the treatment of spine trauma patients. In this context, the outcomes as assessed by these tools could be related to many clinical characteristics including the type of fractures, the provided treatments and radiological results.