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The Development and Psychometric Properties of the Patient Self-Report Neck Functional Status Questionnaire (NFSQ).

STUDY DESIGN
Retrospective analysis of cross-sectional data.


OBJECTIVE
To describe the development of a new self-report Neck Functional Status Questionnaire (NFSQ) and to assess its psychometric properties and practical application. The NFSQ was designed to assess functional status in patients with cervical (spine) disorders who seek outpatient therapy.


BACKGROUND
Many patients seek outpatient therapy due to cervical disorders. Currently, no patient-reported outcome measures exist that capture the ability to perform functional activity in a manner that reflects the experience of this patient population.


METHODS
Four hundred thirty-nine patients who were being treated for cervical disorders responded to a set of survey questions to assess activity-related functional outcomes associated with cervical disorders. Using item response theory, we assessed candidate items for unidimensionality and local independence, item fit, person separation, precision, targeting, and differential item functioning. We also compared discriminant validity of functional status measures estimated by the item response theory model (NFSQ fixed) and measures generated using a simulated computerized adaptive test (NFSQ computerized adaptive test).


RESULTS
Based on expert opinion and subsequent processing and analyses, a final set of 28 items was used to develop the NFSQ. Unidimensionality and local independence were supported. The mean ± SD sample ability level of 57.6 ± 14.3 (scale range, 0-100) matched well with the mean item difficulty of the NFSQ of 51.3 ± 7.4. Differential item functioning was negligible for levels of age group, sex, and symptom acuity. The NFSQ computerized adaptive test measures were as precise as the NFSQ fixed measures.


CONCLUSION
Study results supported the preliminary validity of the 28-item NFSQ for use in assessing patients with different levels of functional status related to their cervical disorders in outpatient rehabilitation settings.