Cross-cultural adaptation and psychometric properties of the Italian version of the Patient-Specific Functional Scale (PSFS) in subjects with shoulder pain

Abstract

Purpose

To cross-culturally adapt the Patient-Specific Functional Scale (PSFS) into Italian and study its classic psychometric properties in subjects with shoulder pain (SP).

Materials and Methods

The PSFS was translated into Italian and administered to 109 SP subjects. Acceptability (time to administer, floor and ceiling effects), reliability (internal consistency [Cronbach’s alpha], test-retest reliability [Intraclass Correlation Coefficient (ICC)], and measurement error [Standard Error of Measurement (SEM), Minimal Detectable Change, (MDC)]), were assessed. Moreover, construct validity was investigated through a-priori hypothesis testing, comparing the PSFS with the Disability of the Shoulder, Arm and Hand (DASH) scale, 36-item Short Form Health Survey (SF-36) and Numeric Pain Rating scale (NPRS).

Results

The PSFS was successfully adapted into Italian, and its acceptability was satisfied. Internal consistency was high (Cronbach’s alpha = 0.925), and test-retest reliability was good (ICC = 0.866, 95% CI = 0.749–0.931). A SEM of 0.7 points and an MDC of 1.9 points were obtained. We observed moderate evidence for construct validity, with 4/6 correlations between other measures being respected.

Conclusion

This study provided reliability and validity of the PSFS in a sample of Italian SP subjects. Future studies should assess the responsiveness of using the PSFS as an outcome measure to capture clinical changes after treatment.

IMPLICATION FOR REHABILITATION

• The Patient-Specific Functional Scale is a reliable, and easy-to-use patient-reported outcome measure.

• The Patient-Specific Functional Scale was cross-cultural validated in the Italian language.

• The Patient-Specific Functional Scale has excellent internal consistency, high reliability, low measurement error, and moderate construct validity in subjects with shoulder pain.

• The Patient-Specific Functional Scale can be used in clinical practice by Italian physiotherapists to assess subjects with shoulder pain.

Keywords:

• Shoulder pain
• patient reported outcome measures
• psychometrics
• validation study
• rehabilitation

Acknowledgments

The authors want to thank Prof. Paul Stratford for helping define the study’s methodology and Dr. Elena Lanfranchi for helping collect the data.

Disclosure statement

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Additional information

Funding

The research activity of Matteo Cioeta, Sanaz Pournajaf, and Michela Goffredo was supported by the Italian Ministry of Health (Ricerca Corrente).