Cross-Cultural Validity and Differential Item Functioning of the Orthotics and Prosthetics Users' Survey With Swedish and United States Users of Lower-Limb Prosthesis.

OBJECTIVES: To investigate the cross-cultural validity of the Orthotics and Prosthetics Users' Survey (OPUS), to evaluate differential item functioning (DIF) related to country, sex, age, amputation level, and amputated side (unilateral, bilateral), and to determine known-group validity of the OPUS. DESIGN: Survey. SETTING: Outpatient clinics. PARTICIPANTS: The sample (N=321) consisted of Swedish (n=195) and U.S. (n=126) adults using lower-limb prostheses. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Four OPUS modules were used: lower extremity functional status, client satisfaction with device (CSD), client satisfaction with services (CSS), and health-related quality of life. Rasch analysis was used to calculate measures for persons and items. RESULTS: The cross-cultural validity was satisfactory. Many items demonstrated DIF related to country and demographic characteristics, but the impact on mean person measures was negligible. The rating scales of CSD and CSS needed adjustments, and the unidimensionality of CSD and CSS was weak. The differences between the mean measures of known patient groups were statistically significant for 2 out of 6 comparisons. CONCLUSIONS: This study supports the validity of OPUS measure comparisons between Sweden and the United States and between subgroups with different demographic characteristics. Some of the country-related DIF may reflect the different health care financing systems. The findings demonstrate that the OPUS can discriminate between certain patient groups. The results also challenge some of our preconceptions about persons with bilateral amputation, indicating that we might know these persons less well than we think.

Test-retest reliability and rater agreements of assessment of capacity for myoelectric control version 2.0.

The Assessment of Capacity for Myoelectric Control (ACMC) is an observation-based tool that evaluates ability to control a myoelectric prosthetic hand. Validity evidence led to ACMC version 2.0, but the test-retest reliability and minimal detectable change (MDC) of the ACMC have never been evaluated. Investigation of rater agreements in this version was also needed because it has new definitions in certain rating categories and items. Upper-limb prosthesis users (n = 25, 15 congenital, 10 acquired; mean age 27.5 yr) performed one standardized activity twice, 2 to 5 wk apart. Activity performances were videorecorded and assessed by two ACMC raters. Data were analyzed by weighted kappa, intraclass correlation coefficient (ICC), and Bland-Altman method. For test-retest reliability, weighted kappa agreements were fair to excellent (0.52 to 1.00), ICC2,1 was 0.94, and one user was located outside the limits of agreement in the Bland-Altman plot. MDC95 was less than or equal to 0.55 logits (1 rater) and 0.69 logits (2 raters). For interrater reliability, weighted kappa agreements were fair to excellent in both sessions (0.44 to 1.00), and ICC2,1 was 0.95 (test) and 0.92 (retest). Intrarater agreement (rater 1) was also excellent (ICC3,1 0.98). Evidence regarding the reliability of the ACMC is satisfactory and MDC95 can be used to indicate change.

Influence of standardized activities on validity of Assessment of Capacity for Myoelectric Control.

The Assessment of Capacity for Myoelectric Control (ACMC) is an observation-based clinical tool that evaluates ability to control a myoelectric prosthetic hand during bimanual activities. Two validity aspects were investigated: potential bias interaction between prosthesis users and activities performed during assessment, and potential bias interaction between activities and different user characteristics (sex or prosthetic side). Six activities were standardized for the ACMC. Upper-limb myoelectric prosthesis users (47 congenital, 11 acquired; 31 male, 27 female, average age 19.9 yr) performed three standardized activities, each on one occasion. Bias-interaction analysis in the many-facet Rasch model identified inconsistent patterns in the interactions of individual users and activity facets and between activities and user characteristics. The standardized activities had no significant influence on measures of user ability. The activities functioned similarly across both sexes (p-value greater than or equal to0.12) and across both prosthetic sides in persons with upper-limb reduction deficiency (p-value greater than or equal to0.50) and persons with acquired amputation (p-value greater than or equal to0.13). The results provide evidence for the validity of the ACMC across the standardized activities and support use of the ACMC in prosthesis users of both sexes and prosthetic sides. The newly standardized activities are recommended for future ACMC use.

Upper limb prosthetic outcome measures: review and content comparison based on International Classification of Functioning, Disability and Health.

The International Classification of Functioning, Disability and Health (ICF) has been recommended as a framework for evaluation of aspects of health. The aim of this study was to compare the contents of outcome measures for upper limb prosthesis users by using the ICF. Measurement focus and psychometric properties of these measures were also investigated. Outcome measures that used upper limb prosthesis users as subjects in their development and psychometric evaluations were selected. The psychometric studies (n = 14) were reviewed and scored and the items in the measures were linked to the ICF. One measure for all ages (ACMC), five paediatric measures (CAPP-FSI, CAPP-PSI, PUFI, UBET and UNB) and two adult measures (OPUS and TAPES) were selected. The concepts extracted (n = 393) were linked to 54 categories in the ICF. The ACMC, CAPP-FSI, UBET, UNB and PUFI measure categories mostly under the ICF component 'Activity and participation'. The TAPES and OPUS also measure ICF categories that describe the emotional and social status of a person. The main conclusion is that the use of a mixture of outcome measures would give a better picture on the aspects of our clients. Measures that focus on the social interaction in paediatric users are required.

Assessment of capacity for myoelectric control: evaluation of construct and rating scale.

OBJECTIVE: To examine the construct and rating scale of the Assessment of Capacity for Myoelectric Control, an assessment to evaluate ability in using a prosthetic hand. DESIGN: Cross-sectional study. SUBJECTS: Upper limb prosthesis users with different prosthetic levels/sides and prosthetic experience were included (n = 96). METHODS: Subjects' assessments with the Assessment of Capacity for Myoelectric Control were collected by 6 raters during their regular hospital visits. Rasch analysis was used, since it allowed an analysis of the data at the item and category levels. Dimension, item hierarchy and item fit statistics were used to examine the construct. Different Rasch parameters were used to examine rating scale structure and its use. RESULTS: The consistency of item difficulties with clinical knowledge and the unidimensionality confirmed that the construct is valid. Two items functioned unexpectedly (misfit), but the misfit was idiosyncratic to the sample, not systematic to the items. The 4-point rating scale usefully differentiated the subjects on the basis of their abilities. The use of category 2 was somewhat redundant. CONCLUSION: The Assessment of Capacity for Myoelectric Control is a valid assessment that evaluates ability in using a prosthetic hand. Revision of the category 2 definition would improve the functioning of the rating scale.