Cost-effectiveness of an Emergency Department-Based Intensive Care Unit

IMPORTANCE

Value in health care is quality per unit cost (V = Q/C), and an emergency department-based intensive care unit (ED-ICU) model has been associated with improved quality. To assess the value of this care delivery model, it is essential to determine the incremental direct cost of care.

OBJECTIVE

To determine the association of an ED-ICU with inflation-adjusted change in mean direct cost of care, net revenue, and direct margin per ED patient encounter.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective economic analysis evaluated the cost of care delivery to patients in the ED before and after deployment of the Joyce and Don Massey Family Foundation Emergency Critical Care Center, an ED-ICU, on February 16, 2015, at a large academic medical center in the US with approximately 75 000 adult ED visits per year. The pre-ED-ICU cohort was defined as all documented ED visits by patients 18 years or older with a complete financial record from September 8, 2012, through June 30, 2014 (660 days); the post-ED-ICU cohort, all visits from July 1, 2015, through April 21, 2017 (660 days). Fiscal year 2015 was excluded from analysis to phase in the new care model. Statistical analysis was performed March 1 through December 30, 2021.

EXPOSURES

Implementation of an ED-ICU.

MAIN OUTCOMES AND MEASURES

Inflation-adjusted direct cost of care, net revenue, and direct margin per patient encounter in the ED.

RESULTS

A total of 234 884 ED visits during the study period were analyzed, with 115 052 patients (54.7% women) in the pre-ED-ICU cohort and 119 832 patients (54.5% women) in the post-ED-ICU cohort. The post-ED-ICU cohort was older (mean [SD] age, 49.1 [19.9] vs 47.8 [19.6] years; P < .001), required more intensive respiratory support (2.2% vs 1.1%; P < .001) and more vasopressor use (0.5% vs 0.2%; P < .001), and had a higher overall case mix index (mean [SD], 1.7 [2.0] vs 1.5 [1.7]; P < .001). Implementation of the ED-ICU was associated with similar inflation-adjusted total direct cost per ED encounter (pre-ED-ICU, mean [SD], $4875 [$15 175]; post-ED-ICU, $4877 [$17 400]; P = .98). Inflation-adjusted net revenue per encounter increased by 7.0% (95% CI, 3.4%-10.6%; P < .001), and inflation-adjusted direct margin per encounter increased by 46.6% (95% CI, 32.1%-61.2%; P < .001).

CONCLUSIONS AND RELEVANCE

Implementation of an ED-ICU was associated with no significant change in inflation-adjusted total direct cost per ED encounter. Holding delivery costs constant while improving quality demonstrates improved value via the ED-ICU model of care.

Laboratory evolution of one disulfide isomerase to resemble another

It is often difficult to determine which of the sequence and structural differences between divergent members of multigene families are functionally important. Here we use a laboratory evolution approach to determine functionally important structural differences between two distantly related disulfide isomerases, DsbC and DsbG from Escherichia coli. Surprisingly, we found single amino acid substitutions in DsbG that were able to complement dsbC in vivo and have more DsbC-like isomerase activity in vitro. Crystal structures of the three strongest point mutants, DsbG K113E, DsbG V216M, and DsbG T200M, reveal changes in highly surface-exposed regions that cause DsbG to more closely resemble the distantly related DsbC. In this case, laboratory evolution appears to have taken a direct route to allow one protein family member to complement another, with single substitutions apparently bypassing much of the need for multiple changes that took place over approximately 0.5 billion years of evolution. Our findings suggest that, for these two proteins at least, regions important in determining functional differences may represent only a tiny fraction of the overall protein structure.

Mammalian Crumbs3 is a small transmembrane protein linked to protein associated with Lin-7 (Pals1)

Drosophila Crumbs is a transmembrane protein that plays an important role in epithelial cell polarity and photoreceptor development. Overexpression of Crumbs in Drosophila epithelia expands the apical surface and leads to disruption of cell polarity. Drosophila Crumbs also interacts with two other polarity genes, Stardust and Discs Lost. Recent work has identified a human orthologue of Drosophila Crumbs, known as CRB1, that is mutated in the eye disorders, retinitis pigmentosa and Leber congenital amaurosis. Our work has demonstrated that human CRB1 can form a complex with mammalian orthologues of Stardust and Discs Lost, known as protein associated with Lin-7 (Pals1) and Pals1 associated tight junction (PATJ), respectively. In the current report we have cloned a full length cDNA for a human paralogue of CRB1 called Crumbs3 (CRB3). In contrast to Drosophila Crumbs and CRB1, CRB3 has a very short extracellular domain but like these proteins it has a conserved intracellular domain that allows it to complex with Pals1 and PATJ. Mouse and human CRB3 have identical intracellular domains but divergent extracellular domains except for a conserved N-glycosylation site. CRB3 is localized to the apical surface and tight junctions but the conserved N linked glycosylation site does not appear to be necessary for CRB3 apical targeting. CRB3 is a specialized isoform of the Crumbs protein family that is expressed in epithelia and can tie the apical membrane to the tight junction.

The carboxyl terminus of zona occludens-3 binds and recruits a mammalian homologue of discs lost to tight junctions

Mammalian homologues of the Drosophila polarity proteins Stardust, Discs Lost, and Crumbs have been identified as Pals1, Pals1-associated tight junction protein (PATJ), and human Crumbs homologue 1 (CRB1), respectively. We have previously demonstrated that PATJ, Pals1, and CRB1 can form a tripartite tight junction complex in epithelial cells and that PATJ recruits Pals1 to tight junctions. Here, we observed that the Pals1/PATJ interaction was not crucial for the ultimate targeting of PATJ itself to tight junctions. This prompted us to examine if any of the 10 post-synaptic density-95/Discs Large/zona occludens-1 (PDZ) domains of PATJ could bind to the carboxyl termini of known tight junction constituents. We found that the 6th and 8th PDZ domains of PATJ can interact with the carboxyl termini of zona occludens-3 (ZO-3) and claudin 1, respectively. PATJ missing the 6th PDZ domain was found to mislocalize away from cell contacts. Surprisingly, deleting the 8th PDZ domain had little effect on PATJ localization. Finally, reciprocal co-immunoprecipitation experiments revealed that full-length ZO-3 can associate with PATJ. Hence, the PATJ/ZO-3 interaction is likely important for recruiting PATJ and its associated proteins to tight junctions.

The Maguk protein, Pals1, functions as an adapter, linking mammalian homologues of Crumbs and Discs Lost

Membrane-associated guanylate kinase (Maguk) proteins are scaffold proteins that contain PSD-95-Discs Large-zona occludens-1 (PDZ), Src homology 3, and guanylate kinase domains. A subset of Maguk proteins, such as mLin-2 and protein associated with Lin-7 (Pals)1, also contain two L27 domains: an L27C domain that binds mLin-7 and an L27N domain of unknown function. Here, we demonstrate that the L27N domain targets Pals1 to tight junctions by binding to a PDZ domain protein, Pals1-associated tight junction (PATJ) protein, via a unique Maguk recruitment domain. PATJ is a homologue of Drosophila Discs Lost, a protein that is crucial for epithelial polarity and that exists in a complex with the apical polarity determinant, Crumbs. PATJ and a human Crumbs homologue, CRB1, colocalize with Pals1 to tight junctions, and CRB1 interacts with PATJ albeit indirectly via binding the Pals1 PDZ domain. In agreement, we find that a Drosophila homologue of Pals1 participates in identical interactions with Drosophila Crumbs and Discs Lost. This Drosophila Pals1 homologue has been demonstrated recently to represent Stardust, a crucial polarity gene in Drosophila. Thus, our data identifies a new multiprotein complex that appears to be evolutionarily conserved and likely plays an important role in protein targeting and cell polarity.