Towards an instrument targeting mobility-related participation: Nordic cross-national reliability

To investigate test-retest reliability and internal consistency of a new instrument for evaluation of mobility device interventions.

The instrument comprised 4 scales and one summed index. Two test-retest interviews involved 147 mobility device users (mean age 60 years) with a broad range of functional limitations, living at home.

For 2 scales and the summed index the reliability was substantial or almost perfect (kappa 0.71/ kappaW 0.76/intraclass correlation coefficient = 0.93; confidence interval = 0.90-0.95). The reliability of one scale was moderate (kappaW 0.41), but after reduction of grades and combination with another scale, it was substantial (kappaW 0.66). The reliability of the fourth scale was moderate (kappaW 0.55). The internal consistency of 3 scales varied from alpha 0.63 to 0.76.

Even though the test-retest reliability of all but one of the scales of the new instrument was substantial to almost perfect, this study demonstrated that revision is required. The challenges identified were probably due to the highly complex relationship between outdoor participation while using mobility devices and accessibility to the outdoor physical environment. Thus, based on the results of this study the instrument will be revised and subsequently launched as the "Nordic mobility-related participation outcome evaluation of assistive device intervention" (NOMO instrument). More research on the concept of mobility-related participation and the psychometric qualities of the instrument is required.