Measuring Emergency Department Acuity

Area of Science:

• Health Services Research
• Emergency Medicine
• Healthcare Analytics

Background:

• Emergency Department (ED) acuity reflects patient illness severity, urgency, and resource intensity.
• Understanding the relative performance of common ED acuity measures is crucial but not well-established.

Purpose of the Study:

• To evaluate the association strength of common ED acuity proxy measures with a comprehensive measure of ED acuity.
• To identify which proxy measures best represent the true acuity spectrum in an ED setting.

Main Methods:

• Retrospective cross-sectional analysis of ED-level data.
• Used proportion of high-acuity charts (PHAC) as the reference standard, defined by specific Ambulatory Payment Classifications (APCs).
• Assessed associations using Spearman's rank correlation and regression models.

Main Results:

• Univariate analysis showed significant associations for ESI scores 1 or 2, case mix index (CMI), academic status, and ED volume, but none explained over 16% of PHAC variation.
• In multivariable regression, only academic status remained significantly associated with PHAC.
• Emergency Severity Index demonstrated the strongest association with PHAC, followed by CMI and ED volume.

Conclusions:

• The Emergency Severity Index (ESI) is the strongest single predictor among commonly used measures for ED acuity.
• Academic status captures unique acuity variability not explained by other common proxies.
• Current common ED acuity measures, even combined, explain only a limited portion (42.6%) of acuity variation, indicating a need for improved measurement tools.