Heterogeneity in functional status among moderately frail older adults: improving predictive performance using a modified approach of subgrouping the Clinical Frailty Scale

PURPOSE: Moderately frail individuals [Clinical Frailty Scale (CFS) 6] demonstrate heterogeneity in basic activities of daily living (bADL). We aimed to establish whether functional dependency in moderate frailty predicts poorer outcomes and examined the utility of subgrouping the CFS in predicting mortality and institutionalisation. METHODS: We prospectively studied 201 hospitalised frail patients (89.5 ± 4.7 years, female 70.1%). We examined Katz Index (KI) against adverse outcomes in CFS6 (n = 106). We then compared predictive performances of a modified CFS version 1 (mCFS-1; category 6A: CFS6 and KI ≥ 2; 6B: CFS6 and KI ≤ 1) and modified CFS version 2 (mCFS-2; category 6A: CFS6 and KI ≥ 2; 6B1: CFS6, KI ≤ 1 and feeding independent; 6B2: CFS6, KI ≤ 1 and feeding dependent) against the CFS. Multivariate analysis was used to compare each tool against mortality and institutionalisation. Receiver operator characteristic analysis was performed to determine area under curve and optimal cut-points for each tool. RESULTS: KI ≤ 1 in CFS6 was associated with higher 12-month mortality (39.3% vs. 15.6%, p = 0.01); amongst KI items, feeding dependent predicted 12-month mortality (p < 0.05). Using mCFS-1, category 6A did not increase 12-month mortality compared with category 5 (OR 1.83, 95% CI 0.52–6.47), unlike category 6B (OR 6.33, 95% CI 2.07–19.33). mCFS-2 produced higher mortality in category 6B1 (OR 5.19, 95% CI 1.30–20.69) and 6B2 (OR 6.92, 95% CI 2.14–22.35). Similar observations were seen for institutionalisation. Optimal cut-point for 12-month mortality was category 6 for CFS, and 6B and 6B1 for mCFS-1 and mCFS-2, respectively. CONCLUSION: This study corroborates the heterogeneity of functional status in moderately frail individuals and validates the use of a modified approach to subgrouping the CFS6 via bADL functional status for improved predictive performance. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s41999-020-00418-8) contains supplementary material, which is available to authorized users.