Relationship of the Patient-Specific Functional Scale to commonly used clinical measures in hand osteoarthritis

STUDY DESIGN: Prospective cohort correlation study. INTRODUCTION: There is no known published research on correlations between the Patient-Specific Functional Scale (PSFS), hand grip strength, and the Disability of the Arm, Shoulder and Hand (DASH) in a population with hand osteoarthritis (OA). PURPOSE: The purpose of this study is to establish reliability of the PSFS and to evaluate the relationship between the PSFS, hand grip strength, and the DASH for a population with hand OA. METHODS: Thirty-five participants in 4 hand clinics completed the PSFS, hand grip strength testing, and the DASH at the onset of therapy and at discharge. Eighteen participants enrolled at the primary investigator's site completed a baseline PSFS one week before the pretreatment collection with data used to establish relative and absolute reliability. Data were analyzed separately at pretreatment and posttreatment with Spearman's rho correlation (P < .05). Intraclass correlation (2, 1), standard error of the measurement, and minimum detectable change (MDC90 and MDC95) were calculated from the repeated baseline and pretreatment PSFS. RESULTS: Intraclass correlation for PSFS was (r = 0.80) with the standard error of the measurement = 0.56, MDC90 = 1.30, and MDC95 = 1.56. Small correlation between the PSFS and DASH scores was found pretreatment (ρ = -0.10) and change scores (ρ = 0.13). CONCLUSION: Excellent reliability with small measurement error has established clinical utility of the PSFS for the population with hand OA. These outcome measures were shown to measure different constructs and therefore should not be used interchangeably. LEVEL OF EVIDENCE: 3.