The Shoulder Pain and Disability Index: The Construct Validity and Responsiveness of a Region-Specific Disability Measure

Abstract

Background and Purpose. The purposes of this study were (1) to assess the construct validity of the Shoulder Pain and Disability Index (SPADI) and (2) to determine whether the SPADI is more responsive than the Sickness Impact Profile (SIP), a generic health status measure. Subjects. The sample consisted of 94 patients who were diagnosed with a shoulder problem and referred to six outpatient physical therapy clinics. Methods. Clinically meaningful change was determined by use of an ordinal rating scale designed to determine whether the patient's shoulder function was improved, the same, or worse following treatment. Spearman rho correlations were calculated for the initial visit SPADI and SIP scores. The standardized response mean (SRM) was used to measure responsiveness for the patients who were judged to be improved. One-tailed paired t tests (α=.01) were used to determine whether differences existed among SRM values. Results. Correlations between the SPADI and SIP scores ranged from r=.01 to r=.57. The SRM value was higher for the SPADI total score (SRM=1.38) than for the SIP total score (SRM=0.79). Conclusion and Discussion. Most correlations between SPADI and SIP scores provided support for the construct validity of the SPADI. The SPADI does not appear to strongly reflect occupational and recreational disability and is more responsive than the SIP.