Prognosis for older people at presentation to emergency department based on frailty and aggregated vital signs

Abstract

Background: Risk stratification for older people based on aggregated vital signs lack the accuracy to predict mortality at presentation to the Emergency Department (ED). We aimed to develop and internally validate the Frailty adjusted Prognosis in ED tool (FaP-ED) for 30-day mortality combining frailty and aggregated vital signs. Methods: Single-center prospective cohort of undifferentiated ED patients aged 65 or older, consecutively sampled upon ED presentation from a tertiary Emergency Center. Vital signs were aggregated using the National Early Warning Score (NEWS) as a measure of illness or injury severity and frailty was assessed with the Clinical Frailty Scale (CFS). The FaP-ED was constructed by combining NEWS and CFS in multivariable logistic regression. The primary outcome was 30-day mortality. Measures of discrimination and calibration were assessed to evaluate predictive performance and internally validated using bootstrapping. Results: 2250 patients were included, 67 (1.8%) were omitted from analyses due to missing CFS, loss to follow-up, or terminal illness. Thirty-day mortality rate was 5.4% (N = 122, 95% CI = 4.5%–6.4%). Median NEWS was 1 (Inter-Quartile Range (IQR): 0–3) and median CFS was 4 (IQR: 3–5). The Area Under Receiver Operating Characteristic (AUROC) for FaP-ED was 0.86 (95% CI = 0.83–0.90). This was significantly higher than NEWS (0.81, 95% CI = 0.77–0.85, DeLong: Z = 3.5, p < 0.001) or CFS alone (0.82, 95% CI = 0.78–0.86, DeLong: Z = 4.4, p < 0.001). Bootstrapped estimates of FaP-ED AUROC, calibration slope, and intercept were 0.86, 0.95, and −0.09, respectively, suggesting internal validity. A decision-threshold of CFS 5 and NEWS 3 was proposed based on qualitative comparison of positive Likelihood Ratio at all relevant FaP-ED cutoffs. Conclusion: Combining aggregated vital signs and frailty accurately predicted 30-day mortality at ED presentation and illustrated an important clinical interaction between frailty and illness severity. Pending external validation, the Fap-ED operationalizes the concept of such “geriatric urgency” for the ED setting.