Charles Philip Gabel, MPhD, PT

Abstract
Background Context
Most spine patient-reported outcome measures are divided into neck and back subregions. This prevents their use in the assessment of the whole spine. By contrast, whole-spine patient-reported outcome measures assess the spine from cervical to lumbar as a single kinetic chain. However, existing whole-spine patient-reported outcomes have been critiqued for clinimetric limitations including concerns with practicality.

Purpose
To develop the Spine Functional Index (SFI) as a new whole-spine patient-reported outcome measure that addressed the limitations of existing whole-spine questionnaires; then to determine the SFI’s clinimetric and practical characteristics concurrently with a recognised criterion, the Functional Rating Index (FRI).

Study Design/Setting
Observational cohort study within ten physical therapy outpatient clinics.

Patient Sample
Spine-injured patients were recruited from a convenience sample referred by a medical practitioner to physical therapy. A pilot study (n=52, 57% female, age 47.6±17.5) followed by the main study (n=203, 48% female, age 41.0±17.8) that had an average symptom duration of less than five weeks.

Outcome Measures
SFI, FRI and Numerical Rating Scale (NRS).

Methods
The SFI was developed through three stages: 1) item generation, 2) item reduction with an expert panel and patient focus group, then 3) pilot field testing to provide provisional clinimetric properties, sample size requirements and to determine suitability for a larger study. Participants completed the SFI, FRI and NRS every two weeks for six weeks, then every four weeks until discharge or study completion at six months. Responses were assessed to provide individual psychometric and practical characteristics for both patient-reported outcomes, with the overall performance evaluated by the Measurement of Outcome Measures and Bot clinimetric assessment scales.

Results
The SFI demonstrated high criterion validity with the FRI, (Pearson’s r=0.87, 95%CI), equivalent internal consistency (α=0.91) and a single-factor structure. The SFI and FRI demonstrated suitable reliability (ICC2,1=0.97:0.95), responsiveness (standardized response mean=1.81:1.68), minimal detectable change with 90%CI (6.4%:9.7%), Flesch-scale reading ease (64%:47%) and user errors (1.5%:5.3%). The clinimetric performance was higher for the SFI on the Measurement of Outcome Measures (96%:64%) and on the Bot scale (100%:75%).

Conclusions
The SFI demonstrated sound clinimetric properties with lower response errors, efficient completion and scoring, and improved responsiveness and overall clinimetric performance compared to the FRI. These results indicated that the SFI was suitable for functional outcome measurement of the whole-spine in both the research and clinical settings.

Journal Abstract:  http://www.sciencedirect.com/science/article/pii/S1529943013015982