What can we learn from 68 000 clinical frailty scale scores? Evaluating the utility of frailty assessment in emergency departments

Abstract

Background: Emergency departments (EDs) in England are under significant strain, with increasing attendances and extended wait times, affecting frail older adults. The clinical frailty scale (CFS) has been implemented as a tool to assess frailty in ED settings, but its reliability and predictive accuracy as a screening tool remain debated.

Objective: To evaluate the use and variability of the CFS in EDs and its association with patient outcomes, including discharge rates, length of stay, readmission and mortality.

Methods: A retrospective cohort study of ED attendances at two London (UK) hospitals from 2017 to 2021. Data included CFS scores, demographics, clinical observations and outcomes. Comparative statistics, logistic regression, Cox proportional hazards models and competing risk regression were applied to examine CFS predictive validity.

Results: In a sample of 123 324 ED visits, CFS scores strongly correlated with adverse outcomes: e.g. for long-term mortality (n = 33 475, events = 8871), each CFS single-point increase was associated with a 25% increase in mortality risk (95% CI 1.23-1.26). CFS scores varied significantly between raters and across visits, median difference two levels (interquartile range 1-3). Intraclass correlation coefficient analysis showed that 33.1% of CFS score differences was attributable to between-patient differences, 15.4% to inter-rater differences, with 51.5% residual variance from non-frailty factors, such as acute illness severity.

Conclusion: The CFS is associated with crucial patient outcomes in the ED. Inter-rater variability and potentially confounding factors can limit its consistency. Automation to enhance CFS score reliability should be explored as a means to support proactive management.

Keywords: clinical frailty scale (CFS); electronic health records (EHRs); emergency department (ED); frailty assessment; older people.

Figure 1

Kaplan–Meier survival curves illustrating the discharge probability over a 10-day period for various CFS scores. Each curve represents a different CFS score from 1.5 (very fit/fit) to 9 (terminally ill). The graph highlights a clear trend where the discharge probability decreases as frailty increases. Notably, the curves for CFS scores 6, 7, 8 and 9 closely overlap, indicating that beyond a certain level of frailty, further increases in the frailty score do not significantly affect the likelihood of discharge.

Figure 2

Kaplan–Meier survival curves illustrating survival probability over a 90-day period following ED attendance for various CFS scores. Each curve represents a different CFS score from 1.5 (very fit/fit) to 9 (terminally ill). The graph highlights a distinct trend in which the survival probability decreases as frailty increases.

Figure 3

CFS scores over time for the 12 patients of 68 067 with the most frequent ED attendances. Each panel represents an individual patient. The x-axis shows years since their initial admission. The y-axis indicates the CFS score (range 1–9). Data points represent CFS scores recorded at each ED visit. This figure illustrates significant intra-patient variability in CFS scores over relatively short time periods. For example, the third panel in the first row (green dots) shows a patient scoring first 1(‘Very Fit’) and 8 (‘Very severely frail’) within ~3 months, and then surviving for at least 2 years with scores as low as 3 (‘Managing well’). This variability seems at odds with a CFS score that reflects a relatively stable measure of baseline frailty, highlighting potential inconsistencies in CFS assessment.