High inter-rater reliability of Japanese bedriddenness ranks and cognitive function scores: a hospital-based prospective observational study

BACKGROUND: The statistical validities of the official Japanese classifications of activities of daily living (ADLs), including bedriddenness ranks (BR) and cognitive function scores (CFS), have yet to be assessed. To this aim, we evaluated the ability of BR and CFS to assess ADLs using inter-rater reliability and criterion-related validity. METHODS: New inpatients aged ≥75 years were enrolled in this hospital-based prospective observational study. BR and CFS were assessed once by an attending nurse, and then by a social worker/medical clerk. We evaluated inter-rater reliability between different professions by calculating the concordance rate, kappa coefficient, Cronbach’s α, and intraclass correlation coefficient. We also estimated the relationship of the Barthel Index and Katz Index with the BR and CFS using Spearman’s correlation coefficients. RESULTS: For the 271 patients enrolled, BR at the first assessment revealed 66 normal, 10 of J1, 15 of J2, 18 of A1, 31 of A2, 37 of B1, 35 of B2, 22 of C1, and 32 of C2. The concordance rate between the two BR assessments was 68.6%, with a kappa coefficient of 0.61, Cronbach’s α of 0.91, and an intraclass correlation coefficient of 0.83, thus showing good inter-rater reliability. BR was negatively correlated with the Barthel Index (r = − 0.848, p < 0.001) and Katz Index (r = − 0.820, p < 0.001), showing justifiable criterion-related validity. Meanwhile, CFS at the first assessment revealed 92 normal, 47 of 1, 19 of 2a, 30 of 2b, 60 of 3a, 8 of 3b, 8 of 4, and 0 of M. The concordance rate between the two CFS assessments was 70.1%, with a kappa coefficient of 0.62, Cronbach’s α of 0.87, and an intraclass correlation coefficient 0.78, thus also showing good inter-rater reliability. CFS was negatively correlated with the Barthel Index (r = − 0.667, p < 0.001) and Katz Index (r = − 0.661, p < 0.001), showing justifiable criterion-related validity. CONCLUSIONS: BR and CFS could be reliable and easy-to-use grading scales of ADLs in acute clinical practice or large-scale screening, with high inter-rater reliabilities among different professions and significant correlations with well-established, though complicated to use, instruments to assess ADLs. TRIAL REGISTRATION: UMIN000041051 (2020/7/10). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-021-02108-x.