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Interpreting SARS-CoV-2 Test Results

Educational Objective
To understand how to interpret the results of diagnostic tests and apply them clinically.
1 Credit CME

A 53-year-old woman was referred to the gastroenterology clinic for endoscopy because of a submucosal gastric nodule. She had not received a COVID-19 vaccination and lived in Maryland, which had a 7-day cumulative COVID-19 case rate of 70 per 100 000 individuals at the time of her visit. Review of systems was unremarkable except for intermittent abdominal pain. She had no fever, cough, shortness of breath, difficulty breathing, muscle aches, headache, sore throat, anosmia, dysgeusia, or diarrhea. SARS-CoV-2 reverse transcriptase–polymerase chain reaction (RT-PCR) testing prior to the procedure was performed, in accordance with the American Society of Anesthesiologists Statement on Perioperative Testing1 for monitored anesthesia. Results of preoperative testing are shown in Table 1.

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C. Proceed with endoscopy, the patient is clinically recovered and not contagious

SARS-CoV-2 RT-PCR is the primary diagnostic test for COVID-19 (Medicare reimbursement, $75). The test amplifies targeted nucleic acid sequences to detect SARS-CoV-2 RNA. RT-PCR testing detects SARS-CoV-2 RNA at low levels, with analytic sensitivity of 98% and specificity of 97%.2 Analytic sensitivity and specificity refer to RT-PCR detection of SARS-CoV-2 RNA in laboratory samples, while clinical sensitivity and specificity refer to identifying patients with and without COVID-19. Clinical sensitivity is approximately 90% and clinical specificity is approximately 95%.35 Time from symptom onset, specimen source, and user error all affect clinical sensitivity (Table 2). Sensitivity of RT-PCR to detect patients with SARS-CoV-2 that can be cultured and infect others is 99%; however, specificity is limited by persistent detection of noninfectious viral RNA.4,5,7

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Article Information

Corresponding Author: KC Coffey, MD, MPH, University of Maryland School of Medicine, 10 S Pine St, MSTF 257-B, Baltimore, MD 21201 (karen.coffey@som.umaryland.edu).

Published Online: September 17, 2021. doi:10.1001/jama.2021.16146

Correction: This article was corrected on October 6, 2021, to correct an error in the Discussion that presented an incorrect positive predictive value for a SARS-CoV-2 test. The Discussion has been corrected and indicates that the positive predictive value of the test for the patient was 6.5%.

Conflict of Interest Disclosures: Dr Diekema reported receiving grants from bioMerieux, Inc for clinical research and personal fees for consulting from Inflammatix, Inc and OpGen, Inc for consulting outside the submitted work. Dr Morgan reported receiving grants from the Veterans Association, Agency for Healthcare Research and Quality, and Centers for Disease Control and Prevention and having an editorial role at Nature Springer outside the submitted work. No other disclosures were reported.

Additional Contributions: We thank the patient for granting permission to publish this information.

References
1.
ASA and APSF statement on perioperative testing for the COVID-19 virus. News release. American Society of Anesthesiologists. December 8, 2020. Accessed July 15, 2021. https://www.asahq.org/about-asa/newsroom/news-releases/2020/12/asa-and-apsf-statement-on-perioperative-testing-for-the-covid-19-virus
2.
Hanson KE, Caliendo AM, Arias CA, et al. IDSA Guidelines on the Diagnosis of COVID-19: Molecular Diagnostic Testing. Infectious Diseases Society of America; 2020. Accessed June 7, 2021. https://www.idsociety.org/practice-guideline/covid-19-guideline-diagnostics/
3.
Miller  TE , Garcia Beltran  WF , Bard  AZ ,  et al.  Clinical sensitivity and interpretation of PCR and serological COVID-19 diagnostics for patients presenting to the hospital.   FASEB J. 2020;34(10):13877-13884. doi:10.1096/fj.202001700RRPubMedGoogle ScholarCrossref
4.
Pekosz  A , Parvu  V , Li  M ,  et al.  Antigen-based testing but not real-time polymerase chain reaction correlates with severe acute respiratory syndrome coronavirus 2 viral culture.   Clin Infect Dis. 2021;ciaa1706. doi:10.1093/cid/ciaa1706PubMedGoogle Scholar
5.
Prince-Guerra  JL , Almendares  O , Nolen  LD ,  et al.  Evaluation of Abbott BinaxNOW rapid antigen test for SARS-CoV-2 infection at two community-based testing sites: Pima County, Arizona, November 3-17, 2020.   MMWR Morb Mortal Wkly Rep. 2021;70(3):100-105. doi:10.15585/mmwr.mm7003e3PubMedGoogle ScholarCrossref
6.
Schuit  E , Veldhuijzen  IK , Venekamp  RP ,  et al.  Diagnostic accuracy of rapid antigen tests in asymptomatic and presymptomatic close contacts of individuals with confirmed SARS-CoV-2 infection: cross sectional study.   BMJ. Published online July 27, 2021. doi:10.1136/bmj.n1676Google Scholar
7.
Findings from investigation and analysis of re-positive cases. Korea Centres for Disease Control and Prevention. Published May 2020. Accessed June 7, 2021. https://www.mofa.go.kr/viewer/skin/doc.html?fn=20200521024820767.pdf&rs=/viewer/result/202106
8.
Rhoads  D , Peaper  DR , She  RC ,  et al.  College of American Pathologists (CAP) Microbiology Committee Perspective: caution must be used in interpreting the cycle threshold (Ct) value.   Clin Infect Dis. 2021;72(10):e685-e686. doi:10.1093/cid/ciaa1199PubMedGoogle ScholarCrossref
9.
Interim guidance on ending isolation and precautions for adults with COVID-19. Centers for Disease Control and Prevention. Updated March 16, 2021. Accessed June 7, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/duration-isolation.html
10.
Abu-Raddad  LJ , Chemaitelly  H , Coyle  P ,  et al.  SARS-CoV-2 antibody-positivity protects against reinfection for at least seven months with 95% efficacy.   EClinicalMedicine. 2021;35:100861. doi:10.1016/j.eclinm.2021.100861PubMedGoogle Scholar
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