Validity and reliability of the Turkish version of the patient-specific functional scale in patients with low back pain

Abstract

Background The Patient-Specific Functional Scale (PSFS) is among the most used measures to evaluate physical function. The PSFS has not been translated into Turkish to date. The purpose of the present study was to translate and cross-culturally adapt the PSFS into Turkish (PSFS-T) and to assess its reliability and validity in patients with low back pain. Methods A total of 105 participants completed the PSFS-T, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), and Visual Analogue Scale (VAS) for pain. Sixty-nine participants completed the PSFS-T questionnaire twice in 7 days. The internal consistency of the PSFS-T was assessed using Cronbach's alpha while the Intraclass Correlation Coefficient (ICC) was used to evaluate test-retest reliability. The convergent validity of PSFS-T was determined with ODI, RMDQ, and VAS questionnaires by using Pearson's correlation coefficient analysis. Results The PSFS-T demonstrated acceptable internal consistency (Cronbach's alpha = 0.79) and good test-retest reliability (ICC2,1 = 0.75) with no floor or ceiling issues. The PSFS-T showed a moderate correlation with ODI (Rp =0 .49, p<0.001) and RMDQ (Rp =0 .46, p<0.001). A poor correlation was found between PSFS-T and VAS (Rp = 0.36, p< 0.001). Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC) for the PSFS-T scores were 0.69 and 1.91 respectively Conclusion The Turkish version of PSFS is a valid and reliable instrument for the assessment of low back patients. It may be considered a preferable scale for clinical assessment of Turkish-speaking patients with low back pain.