Diagnosing COVID‐19 in the Emergency Department: A Scoping Review of Clinical Examinations, Laboratory Tests, Imaging Accuracy, and Biases

Abstract

Objective Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) emerged as a global pandemic in early 2020 with rapidly evolving approaches to diagnosing the clinical illness called coronavirus disease (COVID‐19). The primary objective of this scoping review is to synthesize current research of the diagnostic accuracy of history, physical examination, routine laboratory tests, real‐time reverse transcription–polymerase chain reaction (rRT‐PCR), immunology tests, and computed tomography (CT) for the emergency department (ED) diagnosis of COVID‐19. Secondary objectives included a synopsis of diagnostic biases likely with current COVID‐19 research as well as corresponding implications of false‐negative and false‐positive results for clinicians and investigators. Methods A Preferred Reporting Items for Systematic Reviews and Meta‐Analyses–Scoping Review (PRISMA‐ScR)–adherent synthesis of COVID‐19 diagnostic accuracy through May 5, 2020, was conducted. The search strategy was designed by a medical librarian and included studies indexed by PubMed and Embase since January 2020. Results A total of 1,907 citations were screened for relevance. Patients without COVID‐19 are rarely reported, so specificity and likelihood ratios were generally unavailable. Fever is the most common finding, while hyposmia and hypogeusia appear useful to rule in COVID‐19. Cough is not consistently present. Lymphopenia is the mostly commonly reported laboratory abnormality and occurs in over 50% of COVID‐19 patients. rRT‐PCR is currently considered the COVID‐19 criterion standard for most diagnostic studies, but a single test sensitivity ranges from 60% to 78%. Multiple reasons for false‐negatives rRT‐PCR exist, including sample site tested and disease stage during which sample was obtained. CT may increase COVID‐19 sensitivity in conjunction with rRT‐PCR, but guidelines for imaging patients most likely to benefit are emerging. IgM and IgG serology levels are undetectable in the first week of COVID‐19, but sensitivity (range = 82% to 100%) and specificity (range = 87% to 100%) are promising. Whether detectable COVID‐19 antibodies correspond to immunity remains unanswered. Current studies do not adhere to accepted diagnostic accuracy reporting standards and likely report significantly biased results if the same tests were to be applied to general ED populations with suspected COVID‐19. Conclusions With the exception of fever and disorders of smell/taste, history and physical examination findings are unhelpful to distinguish COVID‐19 from other infectious conditions that mimic SARS‐CoV‐2 like influenza. Routine laboratory tests are also nondiagnostic, although lymphopenia is a common finding and other abnormalities may predict severe disease. Although rRT‐PCR is the current criterion standard, more inclusive consensus‐based criteria will likely emerge because of the high false‐negative rate of PCR tests. The role of serology and CT in ED assessments remains undefined.

Epidemiology and clinical features of emergency department patients with suspected and confirmed COVID‐19: A multisite report from the COVID‐19 Emergency Department Quality Improvement Project for July 2020 (COVED‐3)

“…Although the clinical features of COVID‐19 are well described, relatively little has been published about the characteristics of ED patients who undergo testing for SARS‐CoV‐2. For this reason, there are limited data on the accuracy of COVID‐19 diagnostic and clearance strategies in the ED 11 …”

Multicenter registry of United States emergency department patients tested for SARS‐CoV‐2

“…23 The proposed CORC rule can be used to guide the decision whether to test or not, and assuming that accurate likelihood ratios can be produced for diagnostic tests for SARS-CoV-2, the pretest probability criteria derived from this work will allow an estimate of post-test probability. 6,24 With upcoming influenza, respiratory syncytial, and other viral challenges approaching, the need for clinical criteria to exclude or estimate the probability of COVID-19 may increase.…”

“…7 Reports of low test sensitivity for swab reverse transcriptase polymerase chain reaction (rtPCR) tests, and tests that use other nucleic amplification techniques, have raised concern. 4,6,14 Without specific reliable exclusionary criteria, emergency care clinicians cannot make expeditious decisions for each of the tens of millions of ED patients with symptoms consistent with COVID-19, nor can the emergency care system operate efficiently with the potential need to order a SARS-CoV-2 test for each of these patients.…”

COVID-19 Triage and Test Center: Safety, Feasibility, and Outcomes of Low-Threshold Testing

“…A self-referral bias appears likely. Third, as our patients were walk-in patients at the TTC, it must be assumed that this is a rather healthy population, which could cause a possible spectrum bias [ 34 ]. Verification bias appears to be minimal in our study, as almost all patients presenting to the TTC received RT-PCR testing.…”