Comparison of the measurement properties of the Functional Independence and Difficulty Scale with the Barthel Index in community-dwelling elderly people in Japan

The new Functional Independence and Difficulty Scale (FIDS) is a tool for assessing the performance of basic activities of daily living (BADL). Because many BADL measures already exist, it is important to know whether FIDS can offer added benefit over the existing measures. This study compared measurement properties between the FIDS and a representative BADL assessment tool, the Barthel Index (BI). Recruitment of the participants was done on the basis of convenience sampling. Participants were community-dwelling elderly Japanese subjects (n= 314; age ≥65 years) divided into a healthy elderly group [n= 225; subjects not using long-term care insurance (LTCI) services] and frail elderly group (n= 89; subjects using LTCI services). For each group, ceiling effect (percent participation with the maximum score) was calculated, and it was compared between the two scales. Associations between the FIDS, BI and Medical Outcomes Study Short Form 8 Health Survey (SF-8) were evaluated by Spearman correlation coefficient and partial correlations. Partial correlations coefficients to SF-8 were compared between the two scales. FIDS showed a relatively small ceiling effect compared to the BI. Compared to the BI, FIDS showed a significant positive partial correlation with the broader aspect of the SF-8 subscales, but the strength of correlation between FIDS and SF-8 was weak to negligible. The FIDS might be less affected by ceiling effect than the BI. Additional studies using a sufficient number of probability samples are needed to clarify whether FIDS has any benefit over BI in terms of correlations with the SF-8.