Health Policy Journal Club, Health Policy

Health Policy Journal Club: Are You Sick Enough to Need the ED?

Diagnosis-Based Algorithms Aren't Sure Either

Payers and policymakers have shown great interest to reduce "low-acuity" emergency department (ED) visits, as the ED is a costly environment in which to receive care. Some payers have even denied reimbursements for ED care if a visit is later deemed to be "not an emergency." Physicians have rallied to fight against these practices because it conflicts with the Prudent Layperson Standard and can ultimately put them at risk of not being reimbursed and/or patients at risk of being billed for treatment they thought would be covered. The Prudent Layperson Standard was implemented in 1997 to ensure that insurance coverage for emergency medical conditions was based on initial symptoms as opposed to final diagnosis. In other words, someone who presents to the ED for chest pain should not be penalized financially for being diagnosed with heartburn after a myocardial infarction has been ruled out.

There have been systematic attempts to identify low-acuity ED visits by International Classification of Disease (ICD) diagnosis codes, but how valid these algorithms are based on retrospective assignment of these codes is debatable. In a recent study, the authors identified 15 published algorithms that used ICD codes to retrospectively identify low-acuity ED visits. They then applied these algorithms to actual patient data, and assessed the algorithms against each other to see if they were consistent with one another. The results showed that the algorithms were quite inconsistent and failed to reliably characterize the same ED visit as low acuity. The authors then assessed each algorithm's performance against a composite of encounter-level characteristics that may be a better marker for a "low-acuity" visit (eg, clinical and triage data such as triage score of 4 or 5, fewer than 2 diagnostic tests ordered, not admitted, etc.). They found that none of the 15 algorithms performed particularly well against this more clinically oriented composite.

Overall, these findings suggest that algorithms using ICD codes to retrospectively classify ED visits as "low-acuity" are inconsistent and prone to error. While we need to better understand how the U.S. health care system can best allocate its resources for patients with acute, unscheduled health concerns, some of the tools that are being used now to decide if ED visits are necessary may be actively harming patients. This study should give policymakers and payers much pause before implementing policy based on these retrospective methods.


ARTICLE: Chen AT, Muralidharan M, Friedman AB. Algorithms identifying low-acuity emergency department visits: A review and validation study. Health Serv Res. 2022; Online ahead of print. doi: 10.1111/1475-6773.14011.

To characterize and validate the landscape of algorithms that use International Classification of Disease (ICD) codes to identify low-acuity emergency department (ED) visits.

Data sources: Publicly available ED data from the National Hospital Ambulatory Medical Care Survey (NHAMCS).

Study design: We systematically searched for studies that specify algorithms consisting of ICD codes that identify preventable or low-acuity ED visits. We classified ED visits in NHAMCS according to these algorithms and compared agreements using the Jaccard index. We then evaluated the performance of each algorithm using positive predictive value (PPV) and sensitivity, with the reference group specified using low-acuity composite (LAC) criteria consisting of both triage and clinical components. In sensitivity analyses, we repeated our primary analysis using only triage or only clinical criteria for reference.

Data collection: We used the 2011-2017 NHAMCS data, totaling 163,576 observations before survey weighting and after dropping observations missing a primary diagnosis. We translated ICD-9 codes (years 2011-2015) to ICD-10 using a standard crosswalk.

Principal findings: We identified 15 papers with an original list of ICD codes used to identify preventable or low-acuity ED presentations. These papers were published between 1992 and 2020, cited an average of 310 (SD 360) times, and included 968 (SD 1175) codes. Pairwise Jaccard similarity indices (0 = no overlap, 1 = perfect congruence) ranged from 0.01 to 0.82, with mean 0.20 (SD 0.13). When validated against the LAC reference group, the algorithms had an average PPV of 0.308 (95% CI [0.253, 0.364]) and sensitivity of 0.183 (95% CI [0.111, 0.256]).

Overall, 2.1% of visits identified as low acuity by the algorithms died prehospital or in the ED, or needed surgery, critical care, or cardiac catheterization.

Conclusions: Existing algorithms that identify low-acuity ED visits lack congruence and are imperfect predictors of visit acuity.

EMRA + PolicyRx Health Policy Journal Club: A collaboration between Policy Prescriptions and EMRA

As emergency physicians, we care for all members of society, and as such have a unique vantage point on the state of health care. What we find frustrating in our EDs - such as inadequate social services, the dearth of primary care physicians, and the lack of mental health services - are universal problems. As EM residents and fellows,  we learn the management of myocardial infarctions and traumas, and how to intubate, but we are not taught how health policy affects all aspects of our experience in the ED. Furthermore, given our unique position in the health care system, we have an incredible opportunity to advocate for our patients, for society, and for physicians. Yet, with so many competing interests vying for our conference education time, advocacy is often not included in the curricula. This is the gap this initiative aims to fill.  Each month, you will see a review of a new health policy article and how it is applicable to emergency physicians.  

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