ORIGINAL ARTICLE  COVID-19 SECTION Open access

Italian Journal of Emergency Medicine 2021 April;10(1):24-9

DOI: 10.23736/S2532-1285.21.00073-2

Copyright © 2021 THE AUTHORS

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language: English

Sensitivity of IgM and IgG serology for SARS-CoV-2 plus physicians’ gestalt or rRT-PCR for COVID-19 diagnosis

Gabriele CERINI ¹ ✉, Filippo LAGI ², Giuliano DE STEFANO ¹, Andrea NENCIONI ¹, Maddalena OTTAVIANI ¹, Maria G. COLAO ³, Gian M. ROSSOLINI ^{3, 4}, Barbara TOGNETI ⁴, Stefano GRIFONI ¹, Peiman NAZERIAN ¹ ED COVID-19 

¹ Department of Emergency Medicine, Careggi University Hospital, Florence, Italy; ² Unit of Infectious and Tropical Diseases, Department of Experimental and Clinical Medicine, Careggi University Hospital, Florence, Italy; ³ Unit of Microbiology and Virology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy; ⁴ Department of Health and Management, Careggi University Hospital, Florence, Italy

BACKGROUND: The diagnosis of acute infection of COVID-19 remains an important challenge for clinicians. Serology has been used as population screening tool and it was introduced also in some EDs even if its sensitivity in this context was not well known. The aims of the study were to evaluate the accuracy of serology for the diagnosis of COVID-19 in the Emergency Department (ED) and to evaluate if the sensitivity of the physicians’ gestalt and the sensitivity of the first nasopharingeal swab are increased by serology.
METHODS: Patients were prospectively enrolled from April 7 to April 30, 2020. A blood sample for the titration of immunoglobulins IgM and IgG for SARS-Cov-2 was performed in all patients at the same of the nasopharyngeal swab. Physicians, based on clinical features and bedside diagnostic imaging tests, blinded to nasopharyngeal swab and serology results, established if COVID-19 was likely or unlikely (physicians’ gestalt). Final diagnosis was independently established by two experts after review of 30-day follow-up data.
RESULTS: A total of 923 patients was enrolled. 111 (12.4%) had a final diagnosis of COVID-19. Accuracy of IgM and IgG tests for COVID-19 diagnosis were similar (P=0.74). Both sensitivity and specificity of IgM and IgG were similar (P=1 and P= 0.64 respectively). The accuracy of physicians’ gestalt alone (88.1%, CI 95% 84.4-91.9) was similar to the accuracy of physicians’ gestalt plus serology (87.9% CI 95% 84.4-91.3) (P=0.85). Sensitivity of physicians’ gestalt was 80.2% (CI 95% 71.5-87.1) and was only slightly increased by serology (85.6%, CI 95% 77.7-91.5) (P=0.03). The sensitivity of a diagnostic strategy integrating the first nasopharingeal swab with serology to rule out COVID-19 was not significantly different from the sensitivity of nasopharingeal swab alone (91% CI95% 84.1-95.6 vs. 92.8%, CI95% 86.3-96.8) (P=0.5).
CONCLUSIONS: Serology is not accurate for COVID-19 diagnosis in ED and it cannot be used to safely rule out COVID-19 in association with physician’s gestalt or in association with the first nasopharyngeal swab.

KEY WORDS: COVID-19; Diagnosis; Serology; Emergency service, hospital; Pneumonia; Sepsis; Infections