To assess construct validity, correlations were used to examine the relationships of the four instruments with identified constructs expected to correlate at least moderately (>.5) or stronger (.75). Moderate correlations were projected for: 1) self-reported work productivity; 2) perceived exertion at work; and 3) perceived upper-extremity disability. Strong correlations were projected for: 1) generic work role; 2) self-rated difficulty doing work; 3) occupational performance; and 4) occupational satisfaction. The expected correlations occurred most often for the WLQ-16 and the WIS-RA; for both scales these were with self-reported work productivity and perceived upper-extremity disability. The SPS-6 met the expected correlation with self-reported work productivity. The DASH-W demonstrated no predicted correlations.
All of the tools, except the DASH-W, demonstrated known-groups validity. The groups represented current work status (i.e., normal or reduced hours). Significant results meant that those with reduced hours had greater at-work disability.
When asked which of the four tools was most preferred, 44.6% of the respondents selected the RA-WIS. It was also rated best in terms of ease of understanding, length, and making sense. The WLQ-16, though, was rated as slightly better on comprehensiveness. Even though it is not likely that this sample had many arthritis-related issues, they obviously found that they were affected by the same at-work issues. This finding suggests that disability related to arthritis is similar to that of anyone experiencing shoulder or elbow disorders.
Overall, the authors concluded that the WLQ-16 was “the best and most versatile” for measuring at-work disability in workers with shoulder or elbow disorders. This instrument demonstrated the strongest construct validity, although few of the projected correlations were strong. The WLQ-16 also showed good distributive qualities; none of the participants had a floor or ceiling score on the WLQ-16 items.
More study of these two instruments—WLQ-16 and RA-WIS—with arthritis samples needs to be done. An issue that needs to be addressed is whether the types of jobs differ for persons with different diagnoses. When the WLQ was used with patients with RA, they could not answer a number of questions.10 Patients with RA for example, may seek different types of jobs than those who have an injury-related condition or even those who have a different arthritis diagnosis. Because of the chronic nature of the disease, persons with RA may seek work that is not physically demanding. Findings of the study with patients with RA also suggest that such instruments as the Health Assessment Questionnaire (HAQ) may need to be used along with the at-work measure in order to detect functional limitations.
