Criterion-related validity of Bedriddenness Rank with other established objective scales of ADLs, and Cognitive Function Score with those of cognitive impairment, both are easy-to-use official Japanese scales: A prospective observational study.

Aim: Bedriddenness Rank (BR) and Cognitive Function Score (CFS), issued by the Ministry of Health, Labour and Welfare, Japan, are easy-to-use and widely used in the medical and long-term care insurance systems in Japan. This study aims to clarify the criterion-related validity of the CFS with the Mini-Mental State Examination (MMSE) and ABC Dementia Scale (ABC-DS), and to re-evaluate the criterion-related validity of BR with the Barthel Index (BI) or Katz Index (KI) in more appropriate settings and a larger population compared with the previous study.

Methods: A single-center prospective observational study was conducted in an acute care hospital in a suburban city in Japan. All inpatients aged 20 years or older admitted from October 1, 2018 to September 30, 2019. The relationship between BR and the BI and KI, and the relationship between CFS and the MMSE and ABC-DS were analyzed using Spearman's correlation coefficients.

Results: We enrolled 3,003 patients. Of these, 1,664 (56%) patients exhibited normal BR. The median (interquartile range) values of the BI and KI were 100 (65-100) and 6 (2-6), respectively. Spearman's rank correlation coefficients between BR and the BI and KI were -0.891 (p < 0.001) and -0.877 (p < 0.001), respectively. Of the patients, 1,967 (65.5%) showed normal CFS. The median (interquartile range) MMSE of 951 patients with abnormal CFS and ABC-DS of all patients were 15 (2-21) and 117 (102-117), respectively. Spearman's rank correlation coefficients between CFS and MMSE and ABC-DS were -0.546 (p < 0.001) and -0.862 (p < 0.001), respectively.

Conclusions: BR and CFS showed significant criterion-related validity with well-established but complicated objective scales for assessing activities of daily living and cognitive functions, respectively. These two scales, which are easy to assess, are reliable and useful in busy clinical practice or large-scale screening settings.