Abstract
BACKGROUND: Clinical interpretation of patient-reported outcome measures is an essential step in patient-centered care. Interpretation of scores derived from the Neck Functional Status Computerized Adaptive Test (NFS-CAT) has not been studied. OBJECTIVES: To (1) assess the reliability of point estimates and improvement scores, (2) determine thresholds of minimal clinically important improvement (MCII), and (3) develop a functional staging model to facilitate clinical interpretation of NFS-CAT scores. METHODS: A secondary retrospective cohort analysis was performed using data from patients aged 14 to 89 years who started an episode of care for neck impairments during 2016-2017 and completed the NFS-CAT at admission. The reliability of point estimates and of improvement scores was derived from the NFS-CAT standard error of measurement. The MCII was estimated by combining distribution- and anchor-based approaches. A functional staging model was developed to describe clinical meaningfulness of the quantitative scores provided by the NFS-CAT. RESULTS: Of 250 741 patients who completed the NFS-CAT at admission (mean ± SD age, 54 ± 16 years; 65% female), 169 039 (67%) also completed the NFS-CAT at discharge. The standard error of measurement was stable across the measurement continuum, ranging from 3.7 to 3.9 NFS-CAT points. Minimal detectable improvement was 6.8 points at the 90% confidence level. The estimate of the MCII was 8.1 points, with more change points needed to achieve the MCII for patients with lower baseline scores. Large rates of functional staging change during treatment were observed, demonstrating responsiveness of the functional staging model. CONCLUSION: This study demonstrated how the NFS-CAT can be interpreted to better assist clinicians and patients with neck impairments during outpatient rehabilitation. Copyright © 2019 Journal of Orthopaedic & Sports Physical Therapy®