The Patient-Specific Functional Scale: measurement properties in patients with knee dysfunction

Abstract

Background and purpose: Assessing disability is important, and numerous interviewer-assisted and self-report questionnaires are used to accomplish this task. These questionnaires can be classified as being generic, condition or disease specific, or patient specific. The purpose of this study was to determine test-retest reliability, construct validity, and sensitivity to change of the Patient-Specific Functional Scale (PSFS) when applied to patients with knee dysfunction.

Subjects: Subjects were 38 physician-referred patients with knee dysfunction.

Methods: The PSFS and the Medical Outcomes Study 36-Item Short-Form Health Survey were administered at a patient's initial visit and following 2 to 3 weeks of treatment. An assessment of global change was also made by the patient and clinician at follow-up. These measures allowed the assessment of construct validity and sensitivity to change. To obtain an estimate of reliability, the PSFS was also administered within 72 hours of the initial assessment.

Results: Test-retest reliability and sensitivity to change were excellent (intraclass correlation coefficient [type 2,1] R = .84 and Pearson's r = .78, respectively). Validity was also confirmed.

Conclusion and discussion: Previous investigation on persons with low back pain suggested that the PSFS has promising measurement properties. The results of this study provide further evidence supporting the reliability, validity, and efficiency of the PSFS. Further investigation is needed to determine the extent to which the PSFS can be applied across a variety of conditions and age groups.