Head-to-head Rasch comparison of the Prosthesis Evaluation Questionnaire-Mobility Section and the Prosthetic Mobility Questionnaire 2.0 in Italian lower-limb prosthesis users

Background:The Prosthesis Evaluation Questionnaire-Mobility Section (PEQ-MS) and the Prosthetic Mobility Questionnaire (PMQ 2.0) are two validated self-report questionnaires assessing mobility in people with lower-limb amputation. Objective:The aim of this study was to assess and compare the psychometric properties of PEQ-MS and PMQ 2.0 in a sample of 100 Italian lower-limb prosthesis users. Methods:We conducted a secondary Rasch analysis of data from a prospective single-group observational study, comparing the PEQ-MS and PMQ 2.0 head to head and then cocalibrating them onto a common interval-scaled metric, through common-person equating, to compare their operational range. Results:The PMQ 2.0 showed good measurement qualities. The PEQ-MS had acceptable psychometric properties, despite some weakness in item selection. Cocalibration of the two questionnaires indicated that they assess the same underlying construct (prosthetic mobility), but PMQ 2.0 items have a wider range of difficulty (by one logit). Finally, we created a nomogram allowing to "cross-walk" between scores of the two questionnaires. Conclusions:Comparison of the two questionnaires showed that the PMQ 2.0 has a better measurement performance and larger operational range than the PEQ-MS, making it more suitable for assessing lower-limb prosthesis users with a large range of locomotor abilities, in particular those with higher mobility levels.