key: cord-271871-8grkln6o
authors: Singer, J. S.; Cheng, E. M.; Murad, D.; de St. Maurice, A.; Hines, O. J.; Uslan, D. Z.; Garner, O.; Pregler, J.; Bukata, S. V.; Pfeffer, M. A.; Cherry, R. A.
title: Low Prevalence (0.13%) of COVID-19 Infection in Asymptomatic Pre-operative/Pre-procedure Patients at a Large Academic Medical Center Informs Approaches to Perioperative Care
date: 2020-08-14
journal: Surgery
DOI: 10.1016/j.surg.2020.07.048
sha: 
doc_id: 271871
cord_uid: 8grkln6o

Abstract Background The COVID-19 pandemic has resulted in reduced performance of elective surgeries and procedures at medical centers across the U.S. Awareness of the prevalence of asymptomatic disease is critical for guiding safe approaches to operative/procedural services. As COVID-19 PCR testing has been limited largely to symptomatic patients, healthcare workers (HCWs), or to those in communal care centers, data regarding asymptomatic viral disease carriage are limited. Study Design In this retrospective observational case series evaluating UCLA Health patients enrolled in pre-operative/pre-procedure protocol COVID-19 RT-PCR testing between 4/7/20 – 5/21/20, we determine the prevalence of COVID-19 infection in asymptomatic patients scheduled for surgeries and procedures. Results Primary outcomes include the prevalence of COVID-19 infection in this asymptomatic population. Secondary data analysis includes overall population testing results and population demographics. 18 of 4751 (0.38%) patients scheduled for upcoming surgeries and high risk procedures had abnormal (positive/inconclusive) COVID-19 RT-PCR testing results. 6/18 patients were confirmed asymptomatic. 4/18 had inconclusive results. 8/18 had positive results in the setting of recent symptoms or known COVID-19 infection. The prevalence of asymptomatic COVID-19 infection was 0.13%. More than 90% of patients had residential addresses within a 67 mile geographic radius of our medical center, the median age was 58, and there was equal male/female distribution. Conclusions These data demonstrating low levels (0.13% prevalence) of COVID-19 infection in an asymptomatic population of patients undergoing scheduled surgeries/procedures in a large urban area have helped to inform perioperative protocols during the COVID-19 pandemic. Testing protocols like ours may prove valuable for other health systems in their approaches to safe procedural practices during COVID-19.

These data demonstrating low levels (0.13% prevalence) of COVID-19 infection in an asymptomatic 117 population of patients undergoing scheduled surgeries/procedures in a large urban area have helped to 118 inform perioperative protocols during the COVID-19 pandemic. Testing protocols like ours may prove 119 valuable for other health systems in their approaches to safe procedural practices during COVID-19. 120 121 Introduction: 122 SARS-CoV-2, the coronavirus responsible for the COVID-19 global pandemic, was first identified in 123

Wuhan, China, in a cluster of cases of severe pneumonia. 1, 2 Transmission most often occurs through 124 droplet and direct contact, though aerosol spread also occurs. Three animal coronaviruses have recently 125 evolved to become the newest human coronaviruses. These include SARS-CoV, MERS, and SARS-CoV-2, 126 all with potential to cause severe disease, contagion, and resultant pandemic. 3 127 COVID-19 is genetically closely related to SARS-CoV and has emerged as a highly contagious coronavirus 128 with wide variability in severity of disease, 2 often manifesting as a simple common cold, however, 129 potentially progressing to more serious infections like pneumonia and respiratory failure, usually in an 130 otherwise predisposed patient with underlying health conditions. Data exist suggesting that anywhere 131 from 5-75% of those with COVID-19 could be asymptomatic. 4 While the pandemic continues to evolve, 132 at the time of this publication, more than 18 million people have been infected globally, with over 4.8 133 million in the United States, over 150,000 have died in the U.S., and global deaths approach 605,000. 5,6 134 Lethality is approximaty 3.8% globally. 5,6 135 An identified casualty of the COVID-19 global pandemic has been the cancelation or delay of what have 136 been considered elective or non-essential procedures or surgeries. 7, 8 This disruption is a consequence of 137 three operational aims: (1) to maintain low hospital census levels in anticipation of any potential COVID-138 19 surge, (2) to limit unnecessary patient and health care worker (HCW) SARS-CoV-2 exposures, and (3) 139 to reduce consumption of limited supplies including stocks of personal protective equipment ( Approaches could range from continuing to provide care unabated for considerations of associated 158 potential risk and availability of protective equipment, an approach that would be summarily rejected by 159 HCWs and health system leaders, to performing no surgeries or procedures until SARS-CoV-2 has been 160 extinguished, an equally unrealistic approach. 161

In an effort to help inform these discussions, federal, state, and professional society guidance has been 163 published relative to performing surgery during the COVID-19 pandemic. Early in the pandemic, the 164 American College of Surgeons (ACS) and the Centers for Medicare and Medicaid Services proposed 165 recommendations for limiting elective and non-essential procedures. 7,8 Individual states weighed in, 166 with 33 issuing guidance on limiting elective surgeries. 10 There has been greater focus on cancer 167 surgeries with efforts made to balance the elective scheduling of most cancer operations with the risk of 168 disease progression. 11 In a recent publication in the obstetrics and gynecology literature, Cohen, et al. 169 (12) , suggested that in the absence of life-threatening emergencies requiring surgery, non-operative 170 treatment with a delay of surgeries should be adopted. 12, Given the aerosol generating nature of airway 171 surgery and airway management, otolaryngologists and anesthesiologists have been particularly eager 172 to identify best practices to reduce risks of exposure. 13 More recently, the ACS published an updated 173 guideline addressing resumption of elective surgeries. 14 Their recommendations follow several 174 overarching considerations which include balancing regional COVID-19 epidemiologic awareness, 175 sustaining a capable workforce and PPE supply capacity, creating clear patient communication plans 176 addressing COVID-19 testing policies, while designing prioritization processes that adjust to institutional 177 resources and patient needs. 14 This updated ACS guidance reflects the evolving nature of the COVID-19 178 pandemic and supports individualized health system approaches based on local and regional COVID-19 179 epidemiology and health system resources and priorities. Early during the COVID-19 pandemic, our medical center adopted CDC and ACS recommendations to 211 suspend elective surgical and interventional procedures. Starting 4/16/20, UCLA Health implemented 212 universal masking of all healthcare workers and patients/visitors older than two years of age. Beginning, 213 4/7/20, we implemented the following protocol and algorithms for resuming elective surgical and 214 interventional procedures. We introduced universal pre-operative/pre-procedure COVID-19 RT-PCR 215 testing for all patients scheduled for operative procedures requiring the presence of an anesthesiologist 216 or interventional procedures considered high risk for potential exposure to aerosolized virus, or any 217 patient moving through perioperative areas (pre-op/post-anesthesia care unit) where exposures to 218 other large groups may occur. The two day interval was selected to allow for test results to return, to 219 reduce potential interval exposure risk, and to reduce the interval between testing and surgery during 220 which a prior exposure may have converted to active infection. Testing occurs seven days a week. 221 proceduralist is asked to assess potential level of harm to the patient if the procedure would be 227 deferred. If the risk is considered low, the procedure is deferred pending viral clearance. If deferring the 228 procedure would incur perceived harm to the patient, the procedure may proceed using additional 229 perioperative precautionary measures and with airborne precautions using N95 respirator masks. In test was performed at an outside pre-approved lab. 264 A chart review was performed for any patient with abnormal test results to confirm their symptom 265 status at the time of COVID-19 pre-operative or pre-procedure testing. The data set was summarized at 266 the patient level. Some patients had more than one "pre-procedure" COVID-19 test performed for a 267 variety of reasons (rescheduled case dates, etc.). If any of these results was abnormal, only one entry 268 was used in the numerator to calculate prevalence of patients having had abnormal tests. The 269 denominator was discrete patient numbers having had pre-procedure testing performed. Patient-level 270 characteristics including age, race, and residential zip code were similarly extracted and joined to the 271 aforementioned data set. The distance in miles between the center of each subject's residential zip code 272 and our medical center zip code was used as an approximation of the patient's residential distance from 273 the hospital and was calculated using the ZipRadius R package. We compared our pre-operative and pre- Surgeries/procedures for the remaining patients with abnormal test results either proceeded following 305 repeat negative COVID-19 testing or remained deferred due to patient preference. All confirmed cancer-306 related procedures or surgeries proceeded though two patients awaiting biopsies/mass excisions were 307 rescheduled by one month pending repeat testing for viral clearance.. 308

Two patients with positive/detected COVID-19 testing results had residential addresses in Las Vegas, NV. 309

The remaining patients with positive results had residential addresses within a 10 mile radius of our 310 medical center. Table 2 -19 and others may have been diagnosed with COVID-19 infection while awaiting  325 testing. We believe this accounts for the eight symptomatic patients in our study population. 326

As a large urban referral center, we adopted the CDC and ACS recommendations early in the pandemic, 327 suspending elective surgical and interventional procedures, and later relaxing those suspensions while 328 balancing local/regional COVID-19 epidemiology, data regarding our pre-operative/pre-procedure 329 testing results, and health system resources and priorities. Our protocols designed to address COVID-19-330 related disruptions to surgery and procedure performance have guided an approach to prioritizing and 331 safely performing surgical and interventional procedures, balancing the needs of the patient, HCW 332 safety, and PPE supplies. Before all surgical/procedural patients were tested, our protocols for reducing 333 exposures in the operating room included a 20 minute time out following any intubation to allow 334 clearance of potentially aerosolized viral particles before the entire team entered the operating theater 335 for procedure start and included use of additional perioperative and airborne precautionary measures. 336 Information about the very low level of COVID-19 infection in asymptomatic pre-op/pre-procedure 337 patients using our COVID-19 RT-PCR testing with high clinical sensitivity, specificity, and negative 338 predictive value, has provided reassurance to our surgeons, proceduralists, and anesthesiologists and 339 has led to protocol modifications. Given the accuracy of our testing, our healthcare workers are 340 reassured that using standard PPE should provide adequate protection during interactions with patients 341 who have tested negative. Further, for patients with negative surveillance testing, the 20 minute post-342 intubation time out has been lifted and universal donning of N95 respirator masks has been relaxed. At 343 our health system, we continue to require universal masking of all healthcare workers, patients, and 344 visitors older than two years of age. 345

One possible interpretation of our data is that there may be very low levels of COVID-19 infection in 346 those who do not express COVID-like symptoms. Evidence suggests that between 5-75% of patients 347 diagnosed with COVID-19 may be asymptomatic, 4 however, the prevalence of COVID-19 infection in 348 asymptomatic patients is unknown. In interpreting our data, one must consider our catchment 349 population. Patients awaiting surgeries and procedures at our health system may inherently represent a 350 population at lower risk of COVID-19 infection. This patient population likely includes fewer in nursing 351 homes and communal living facilities, where the known prevalence of COVID-19 is higher. Patients 352 awaiting procedures may also practice stricter social distancing in order to avoid COVID-19 exposures 353 that could interfere with their planned procedures. There may be additional inherent differences as 354 regards health insurance coverage and proportion of tertiary/quaternary patients at our medical center 355 compared to higher risk populations. Taken together, these factors could lower the prevalence of 356 disease in our studied population, which represents a sample of the overall LA area demographic 357

When comparing our surgical/procedural population to LA County data, there are clear differences with 358 more whites/Caucasians, older patients, and fewer Hispanics/Latinos in our data set as compared to the 359 greater Los Angeles area population. As highlighted in Figure 2 , our sample population of patients 360 scheduled for upcoming surgeries and procedures represents an overall older population as compared 361 to the greater LA area population demographics. We did see a trend toward younger age for our 362 symptomatic, or recently diagnosed COVID-19 positive, patients, more commensurate with overall LA 363 population demographic data. While the number of patients in this category was too low to determine 364 statistical significance of this trend, we hypothesize that the younger cohort may exercise less strict 365 social distancing, may be more active critical workforce members, and may more likely act as care 366

givers, activities potentially contributing to an increased exposure/infection risk when compared to the 367 overall cohort. 368

As emerging evidence suggests that the prevalence and severity of COVID-19 disease presentations are 369 greater in blacks and Hispanics, one might conclude that our data do not equally represent populations 370 with baseline higher prevalence of disease. 21-23 Though the numbers of patients with abnormal testing in 371 our dataset are too small to calculate statistical significance, we did not see trends toward higher 372 prevalence of asymptomatic or symptomatic disease in under-represented populations as compared to 373 our overall population. The overall very low numbers of COVID-19 positive patients in our data set 374 preclude the ability to extrapolate significance of this finding. 375

Our data do not address the proportion of the regional population that has been exposed and is now 376 immune. Recent data suggest a possible seroprevalence of antibodies to SARS-CoV-2 of 4.65% in Los 377

Angeles County. 24 In that data set, 13% of those tested for antibody to SARS-CoV-2 reported fever with 378 cough, 9% fever with shortness of breath, and 6% loss of smell or taste, suggesting that a proportion of 379 those tested may have been symptomatic for COVID-19 at the time of testing. According to Spellberg, et 380 al., the prevalence of COVID-19 infection in patients with mild flu-like illness treated at another large 381 academic medical center in Los Angeles (LA County-USC), was 5%. 24 They excluded patients with known 382 COVID-19 exposures, recent travel, or severe symptoms but included only patients endorsing mild flu-383 like symptoms. Our data, demonstrating a 0.13% prevalence of asymptomatic COVID-19 infection, may 384 be explained by the nature of our testing a population of patients presumed to be asymptomatic and 385 awaiting scheduled surgeries/procedures. 386

Using a surveillance pre-procedure COVID-19 RT-PCR test with high clinical sensitivity, specificity, and 388 negative predictive value, we found very low levels (0.13% prevalence) of COVID-19 infection in 389 asymptomatic patients undergoing scheduled surgeries/procedures at UCLA Health. Comparing data 390 obtained by similar analyses from other asymptomatic populations would be required before 391 determining scalability of our findings or applying this asymptomatic prevalence data to wider 392 populations. 393

As the scientific community gains further understanding of the pathophysiology of SARS-CoV-2, we 394 continue to evaluate our testing protocols in line with CDC and ACS guidance, with plans to adjust as 395 

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