Evaluating a Widely Implemented Proprietary Deterioration Index Model among Hospitalized Patients with COVID-19

Abstract

Rationale: The Epic Deterioration Index (EDI) is a proprietary prediction model implemented in over 100 U.S. hospitals that was widely used to support medical decision-making during the coronavirus disease (COVID-19) pandemic. The EDI has not been independently evaluated, and other proprietary models have been shown to be biased against vulnerable populations. Objectives: To independently evaluate the EDI in hospitalized patients with COVID-19 overall and in disproportionately affected subgroups. Methods: We studied adult patients admitted with COVID-19 to units other than the intensive care unit at a large academic medical center from March 9 through May 20, 2020. We used the EDI, calculated at 15-minute intervals, to predict a composite outcome of intensive care unit-level care, mechanical ventilation, or in-hospital death. In a subset of patients hospitalized for at least 48 hours, we also evaluated the ability of the EDI to identify patients at low risk of experiencing this composite outcome during their remaining hospitalization. Results: Among 392 COVID-19 hospitalizations meeting inclusion criteria, 103 (26%) met the composite outcome. The median age of the cohort was 64 (interquartile range, 53-75) with 168 (43%) Black patients and 169 (43%) women. The area under the receiver-operating characteristic curve of the EDI was 0.79 (95% confidence interval, 0.74-0.84). EDI predictions did not differ by race or sex. When exploring clinically relevant thresholds of the EDI, we found patients who met or exceeded an EDI of 68.8 made up 14% of the study cohort and had a 74% probability of experiencing the composite outcome during their hospitalization with a sensitivity of 39% and a median lead time of 24 hours from when this threshold was first exceeded. Among the 286 patients hospitalized for at least 48 hours who had not experienced the composite outcome, 14 (13%) never exceeded an EDI of 37.9, with a negative predictive value of 90% and a sensitivity above this threshold of 91%. Conclusions: We found the EDI identifies small subsets of high-risk and low-risk patients with COVID-19 with good discrimination, although its clinical use as an early warning system is limited by low sensitivity. These findings highlight the importance of independent evaluation of proprietary models before widespread operational use among patients with COVID-19.

Keywords: coronavirus disease; deterioration index; prediction model; validation study.

Figure 1.

High-risk analysis plot showing the relationship between the Epic Deterioration Index (EDI) threshold and the sensitivity, specificity, PPV, and NPV, with a histogram demonstrating the distribution of maximum EDI per patient. The high-risk area (≥68.8) is shaded in orange. NPV = negative predictive value; PPV = positive predictive value.

Figure 2.

Distribution of alert times based on exceeding the high-risk threshold (Epic Deterioration Index ≥ 68.8), demonstrating (A) all alerts and (B) alerts in the 24 hours before the outcome, with the first alert highlighted in red. Each point represents a hypothetical alert; no actual alerts were generated.

Figure 3.

Calibration curve comparing deciles of all predicted Epic Deterioration Index (EDI), rescaled to 0 to 1, with the observed risk, with a line demonstrating ideal calibration (solid) and a histogram of predicted EDI.

Figure 4.

Low-risk analysis plot showing the relationship between the Epic Deterioration Index (EDI) score threshold in the first 48 hours and the sensitivity, specificity, PPV, and NPV, with a histogram demonstrating the distribution of maximum EDI per patient. The low-risk area (<37.9) is shaded in green. NPV = negative predictive value; PPV = positive predictive value.

Figure 5.

Four example patients, of whom two experienced an adverse outcome, with shaded risk thresholds. Green (Epic Deterioration Index [EDI] < 37.9) represents low risk, yellow represents intermediate risk (EDI ≥ 37.9 to < 68.8), and orange (EDI ≥ 68.8) represents high risk. EDI scores recorded after the primary outcome are shown in the top panels but were not used in the model validation. The blue line represents transfer to an intensive care unit, and the red line represents the onset of mechanical ventilation.