Development and validity of a work functioning impairment scale based on the Rasch model among Japanese workers

[Abstract] : [Objectives] : The purpose of this study was to develop a new work functioning impairment scale (WFun) and examine its validity. [Methods] : The WFun was developed based on the Rasch model, which consists of seven items. We conducted a pilot study (n=1,000) using an Internet investigation and a field study (n=1,294) in a manufacturing industry, and we additionally collected data from six workplaces from other industries. This series of studies was examined with a Rasch model analyses including item fit statistics as well as hypothesis testing. Convergent validity was used to examined the association of the WFun with the Stanford Presenteeism Scale, SF-8, Work Ability Index, and several types of job disruptions. We also examined differential test functioning. [Results] : All the items showed adequate fit (infit mean-square statistics