Examination of the structural components of the Abilitator-A self-report questionnaire on work ability and functioning aimed at the population in a weak labour market position

According to the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) panel, structural validity describes how well Patient-Reported Outcome Measures' (PROM) scores reflect the dimensions of the measured construct. The main purpose of this study was to examine the structural components of the Abilitator, a co-developed self-report questionnaire on work ability and functioning for the population in a weak labour market position. We examined to what extent the Abilitator has reflective and formative elements in its five summary scales: "C. Inclusion", "D. Mind", "E. Everyday life", "F. Skills", and "G. Body". The Abilitator data sample (n = 4555, men 51%, mean age 37 years) was collected in 2017-2022 by the Finnish Institute of Occupational Health in cooperation with the European Social Fund Priority 5 projects in which the participants have multiple challenges to gain employment. For the structural components and validity analysis we implemented both Confirmatory Factor Analysis (CFA) and Exploratory Factor Analysis (EFA). Based on the COSMIN criteria for structural validity, the Abilitator reached approximate model fit with CFA when we analysed the different concepts of the questionnaire separately rather than in one unified model. An exception was "E. Everyday life" which was a formative summary scale, and it did not reach approximate fit. EFA showed that the items in the Abilitator's summary scales loaded on ten factors. The Abilitator had both reflective and formative elements in its structure. It reached structural validity in those separate concepts that were based on a reflective model. This study revealed interesting connections between different aspects of the Abilitator and produced valuable information for further modification of the questionnaire.