key: cord-0818933-877ok5rt
authors: Sangal, Rohit B.; Peaper, David R.; Rothenberg, Craig; Landry, Marie L.; Sussman, L. Scott; Martinello, Richard A.; Ulrich, Andrew; Venkatesh, Arjun K.
title: Universal SARS-CoV-2 Testing of Emergency Department Admissions Increases Emergency Department Length of Stay
date: 2021-09-08
journal: Ann Emerg Med
DOI: 10.1016/j.annemergmed.2021.09.005
sha: df05bdb819ed708c13adf5cf1efd5e9993410136
doc_id: 818933
cord_uid: 877ok5rt

Background Our institution experienced both a change in SARS-CoV-2 testing policy as well as substantial changes in local COVID-19 prevalence allowing for a unique examination of the relationship between SARS-CoV-2 testing and ED length of stay (LOS). Methods An observational interrupted time series of all patients admitted to an academic health system between March 15, 2020 and September 30, 2020. Given testing limitations from March 15 to April 24, all patients receiving a SARS-CoV-2 test were symptomatic. On April 24, testing was expanded to all ED admissions. The primary and secondary outcome was ED LOS and number needed to test (NNT) to obtain a positive, respectively. Results A total of 70,856 patients were cared for in the EDs during the seven month period. The testing change increased admission LOS by 1.89 hours (SE 0.25, 95% CI: 1.39, 2.38). The NNT was 2.5 patients and was highest yield on April 1, 2020 when the state positivity rate was 39.7%, however the NNT exceeded 170 patients by Sept 1, 2020 at which point the state positivity rate was 0.5%. Discussion While universal SARS-CoV-2 testing of ED admissions may meaningfully support mitigation and containment efforts, the clinical cost of testing all admissions amidst low community positivity is notable. In our system, universal ED SARS-CoV-2 testing was associated with a 24% increase in admission LOS alongside the detection of only one positive case every other day. Given the known harms and risks of ED boarding and crowding, solutions must be developed to support regular operational flow while balancing infection prevention needs.

Despite expanding SARS-CoV-2 testing resources and availability, COVID-19 continues to spread and remains a persistent public health threat. Given evidence of viral transmission by asymptomatic persons, pandemic mitigation efforts necessitate identification of asymptomatic individuals. Depending on local disease prevalence, rates of asymptomatic patients testing positive ranges from 1% to as high as 30%. 1 Within hospitals, identification and isolation of asymptomatic individuals with SARS-CoV-2 has garnered much attention as a method to prevent outbreaks, reduce bed transfers of cohorted patients and to allay fears of hospital acquired COVID-19.

Universal pre-admission patient testing continues to be a challenge. Similar to influenza, identifying which patients require isolation facilitates early cohorting of infected patients which helps to limit staff and patient exposure and allows more efficient bed management. 2, 3 A similar approach has been employed in emergency departments (ED) with regards to However, in low prevalence areas this approach may unnecessarily delay care, given that most molecular tests utilized in hospital-based EDs require extended turnaround times. As ED volumes continue to rebound towards pre-COVID-19 numbers, further extending length of stay (LOS) exacerbates ED crowding and boarding-both of which have both been associated with poor outcomes. 4, 5 Specifically, our institution transitioned from symptomatic to universal SARS-CoV-2 screening of ED admissions congruent with a community prevalence that changed from one of the highest J o u r n a l P r e -p r o o f in the nation in March, 2020 to one of the lowest seven months later. We examined the association between ED-based SARS-CoV-2 screening approaches and ED LOS.

This was an observational interrupted time series of all ED patients seen in tertiary care health system composed of an academic, community and free-standing ED (FSED) with a combined total annual visit volume exceeding 190,000 patients. Functionally, patients could transfer between healthcare system hospitals sites based on inpatient bed availability. Processes for admission were the same across all sites with the only exception being that patients admitted from the FSED were transferred to one of the other two sites upon bed availability. Of note, these EDs do not have observation units and patients in observation are managed by inpatient teams. Given this is a billing distinction without effect on bed assignment, observation or inpatient status was not sub-analyzed. We constructed a dataset inclusive of all ED timestamps, diagnoses and SARS-CoV-2 tests from the institutional data warehouse between March 15 and September 30, 2020. Given testing limitations, from March 15 to April 24, 2020, only patients under investigation (PUIs) with lower respiratory tract infectious symptoms, fever, or clinical suspicion for COVID-19 were tested. On April 24, testing was expanded from symptomatic patients to all ED admissions. While there was greater overall test availability, rapid molecular tests were still limited and preferentially used for ED specimens.

J o u r n a l P r e -p r o o f RT-PCR testing was performed locally using either an emergency use authorized (EUA) variation of the CDC protocol 6 or GeneXpert Xpress (Cepheid). Internal validation data supports the comparability of these assays, and a real-life application of these specific assays has been published. 7 Pre-universal testing PUIs were admitted to an isolation floor, swabbed for SARS-CoV-2 and appropriately reassigned based on results. After universal testing was implemented, GeneXpert Xpress tests were prioritized for the ED and other testing platforms used only if Xpress not available. Samples were not subject to batch loading. Xpress tests were run locally.

The primary analysis examined the relationship between ED testing strategy (symptomatic vs universal) and ED LOS. The primary outcome was ED LOS stratified between admitted and discharged patients. Consistent with national metrics, ED LOS was defined as the time in minutes between ED arrival and ED departure. 8 Boarding LOS, was defined as the time in minutes from ED admit order to ED departure. We constructed autoregressive integrated moving average regression models (ARIMA) adjusting for ED census, ICU admissions, COVID-19 inpatient count, non-COVID-19 inpatient count, net hospital admissions and week of testing. 9 ED census was used as a marker of ED crowding. 10, 11 Hospital active capacity (as opposed to total overall beds) is dependent on staffing resources and can change unpredictably. The daily net hospital admissions were calculated as discharges subtracted from admissions as a proxy for daily changes in hospital capacity which has been adapted from the Scottish Government who used this metric to measure dynamic capacity of COVID-19 patients throughout the pandemic. 12 Of note, the three EDs were pooled because several operational processes such as load balancing J o u r n a l P r e -p r o o f arrivals between EDs, cross campus ED transfers and cross campus hospitalization make LOS a reflection of the total system and not a site specific phenomenon. 13 However site specific analysis is available in the supplement (S4-6). Ten out of 200 (6.5%) of data were imputed using Kalman filtering as justified in prior literature for COVID-19 and ARIMA modeling. 14, 15 The secondary analysis focused on diagnostic yield of ED screening for SARS-CoV-2. The diagnostic yield was measured as the proportion of ED SARS-CoV-2 tests returning a positive result. For this analysis, we report descriptive statistics of the diagnostic yield as well as the number needed to test (NNT) at the weekly level. Furthermore, to provide context we concurrently report the community prevalence of COVID-19 from publicly available information. 16, 17 Data analysis was conducted using R version 3.6.3. This study was approved by the University Investigation Review Board.

A total of 70,856 patients were cared for in the EDs during the seven month study period. There were 11,541 (16.3%) patients in the pre-universal testing period and of these, 3,910 (33.9%) were admitted and 3,364 (86%) were symptomatic and tested. Of the patients seen after the policy change, 18,311 (30.9%) were admitted and all were tested (supplemental figure 1).

Given the setting of declining ED visits and rising ED admissions 18 we found significant effects of the universal testing policy on ED LOS (adjusting for covariates) for admitted patients ( Figure   1 ). The universal testing policy was associated with 1.89 hour increase in ED admitted LOS (SE J o u r n a l P r e -p r o o f 0.25, 95% CI: 1.39, 2.38) and represents a 24% increase in admission LOS (Supplemental Table   1 (Figure 2 ).

As the COVID-19 pandemic evolves across the US with heterogeneous community prevalence and variable access to testing resources in the ED, hospitals will increasingly face the need to make operational decisions balancing COVID-19 mitigation efforts with operational pressures.

We found that the common operational change to universal screening was associated with a 24% increase in ED LOS for admitted patients and that this delay in care was sustained as community prevalence of COVID-19 declined and health system resources rebounded.

Despite increased testing availability, and the ED SARS-CoV-2 rapid test taking as little as 45 minutes laboratory time to complete, overall ED LOS increased. This is due to inefficiencies J o u r n a l P r e -p r o o f related to manual and often fragmented processes around collection, transport, analysis and bedding systems that have a large cumulative effect. Notably, specimens must be hand delivered to the laboratory due to infection prevention concerns about using a pneumatic tube system. Of note, the clinical admission decision was not affected by the policy and the impact of universal testing directly increased boarding times for admitted patients. Qualitatively clinicians ordered this test early during clinical workups but a delay in leaving the ED was still observed. Finally, despite allowing high suspicion COVID-19 patients to be placed on a "COVID-19 Unit" before test results returned, prolonged ED LOS was still observed.

We confirmed the findings of Holmes and colleagues (2020) that there is a low positivity rate among asymptomatic individuals across a broader time frame of seven months (Supplemental figure 2) . There is likely a meaningful infection prevention benefit to universal screening of ED admissions, however it must be balanced with potential harms of ED crowding and inefficient resource use during times of low diagnostic yield. When examining the community positivity rate at the COVID-19 peak compared to its nadir against the number of ED patients needed to test to obtain a positive, the onerous effects are exponential when community prevalence is low. With 100 admissions per day across the EDs, community positivity of 0.5% translates to a NNT of nearly 170. While extended ED LOS may be warranted at times of high community prevalence and higher risk of within hospital transmission, it is less clear at times of low prevalence when a positive test might be expected every other day. This NNT is likely to continue to rise as community vaccination rates improve and the prevalence rate of COVID-19 decreases alongside adherence to other non-pharmaceutical interventions (ie social distancing). However, the effects of COVID-19 variants on viral prevalence are not yet fully understood, and loosening masking J o u r n a l P r e -p r o o f requirements and increasing occupancy limits may further promote community spread.

Furthermore, our NNT estimates are likely conservative given that false positives are more likely at times of low prevalence. A universal testing strategy is needed to identify asymptomatic individuals and can be possible without creating delays by exploring alternative policies related to bedding asymptomatic patients pending SARS-CoV-2 results or less sensitive screening tests with confirmatory molecular tests which has been successful at some institutions. 19 Unfortunately the rapid testing approach with reflex to PCR was not commercially available until late 2020 given initial supply was bought by the federal government. 20 Additionally, early CDC guidance was to not use pneumatic tube systems for SARS-CoV-2 swab transport 21 despite such systems being used with other viral samples to significantly decrease turnaround times associated with sample movement from patient to the laboratory. 22 There are several limitations to this study. First, generalizability may be limited as a single institution, however the conceptual framework of analyzing LOS as a function of testing strategy can be done elsewhere to inform policy decisions. Furthermore, the benefit of this universal testing policy is dependent on the COVID-19 burden in the region so our results must be taken in the context of individual regional COVID-19 trends. Given the dates of the study, vaccines were not yet available and if our hospital relaxed testing for asymptomatic fully vaccinated J o u r n a l P r e -p r o o f individuals, the results may be more muted. To date, despite one of the highest vaccination rates and lowest infection rates in the country, we have not relaxed testing standards. However we could expect that increased vaccinations are likely to only increase the NNT and in turn extend these effects on hospital flow. Finally, we did not explore the patient specific outcomes such as left without being seen, mortality or clinical decompensation within this study.

While universal COVID-19 testing of ED admissions may support mitigation and containment efforts, the clinical cost of testing all ED admissions, particularly amidst low community prevalence, is notable. In our system, universal COVID-19 testing was associated with a nearly three hour increase in ED LOS for all admitted patients alongside the detection of only one positive case every other day. Furthermore, as vaccination reduces community prevalence, innovative admission and infection prevention practices that can facilitate patient admission prior to SARS-CoV-2 testing results may offer a more practical solution to reducing patient exposure to the known harms and risks of ED crowding and boarding. Future research needs to include cost-benefit/effectiveness to better understand how to balance safety and patient experience, and to consider a NNT or community prevalence threshold for initiating/discontinuing asymptomatic testing. 

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