Clinical decision-making in older adults following emergency admission to hospital. Derivation and validation of a risk stratification score: OPERA

Abstract

Objectives of the study: Demographic changes alongside medical advances have resulted in older adults accounting for an increasing proportion of emergency hospital admissions. Current measures of illness severity, limited to physiological parameters, have shortcomings in this cohort, partly due to patient complexity. This study aimed to derive and validate a risk score for acutely unwell older adults which may enhance risk stratification and support clinical decision-making.

Methods: Data was collected from emergency admissions in patients ≥65 years from two UK general hospitals (April 2017- April 2018). Variables underwent regression analysis for in-hospital mortality and independent predictors were used to create a risk score. Performance was assessed on external validation. Secondary outcomes included seven-day mortality and extended hospital stay.

Results: Derivation (n = 8,974) and validation (n = 8,391) cohorts were analysed. The model included the National Early Warning Score 2 (NEWS2), clinical frailty scale (CFS), acute kidney injury, age, sex, and Malnutrition Universal Screening Tool. For mortality, area under the curve for the model was 0.79 (95% CI 0.78-0.80), superior to NEWS2 0.65 (0.62-0.67) and CFS 0.76 (0.74-0.77) (P<0.0001). Risk groups predicted prolonged hospital stay: the highest risk group had an odds ratio of 9.7 (5.8-16.1) to stay >30 days.

Conclusions: Our simple validated model (Older Persons' Emergency Risk Assessment [OPERA] score) predicts in-hospital mortality and prolonged length of stay and could be easily integrated into electronic hospital systems, enabling automatic digital generation of risk stratification within hours of admission. Future studies may validate the OPERA score in external populations and consider an impact analysis.

Fig 1. Receiver operating curves for in-hospital mortality for derivation and validation groups.

(A) derivation and (B) validation groups. OPERA score (Blue line), CFS (Red line) and NEWS2 (Green line). CFS—clinical frailty scale, NEWS2—national early warning score.

Fig 2. Nomogram of derivation model.

Example shown is of an acutely admitted 85-year-old male with a CFS of 7, creatinine 163 μmol/L (baseline 80), high risk MUST, and a NEWS2 of 9. Age 85 = 4 points (one point added for every 5 years above 65), CFS 7 = 14 points (individual CFS multiplied by two), AKI = 4 points, high risk MUST = 2 points (low = 0, medium = 1 and high = 2), male sex = 2 points, NEWS2 of 9 = 9 points (one point for every NEWS2 score). Total OPERA score 35 points. AKI—acute kidney injury, MUST—Malnutrition Universal Screening Tool.

Fig 3. Calibration curve on validation cohort of OPERA points model before and after recalibration.

(A) before recalibration, (B) after recalibration. Reference line, 95% confidence interval, lowess smoothing curve, and the distribution of mortality and survival against predicted probabilities.