key: cord-0751860-tabgw0ai
authors: Di Paolo, Marcello; Iacovelli, Alessandra; Olmati, Federica; Menichini, Ilaria; Oliva, Alessandra; Carnevalini, Martina; Graziani, Elda; Mastroianni, Claudio Maria; Palange, Paolo
title: False-negative RT-PCR in SARS-CoV-2 disease: experience from an Italian COVID-19 unit
date: 2020-07-13
journal: ERJ Open Res
DOI: 10.1183/23120541.00324-2020
sha: 618eceeb14d79e9bd86451e044949e819f51a822
doc_id: 751860
cord_uid: tabgw0ai

False-negative cases of #COVID19 are being increasingly reported. Laboratory diagnosis through RT-PCR testing alone lacks adequate sensitivity to be recommended as the only valid criterion to confirm COVID-19 diagnosis. https://bit.ly/2BLFnEe

In a retrospective cohort of 1014 Chinese patients, AI et al. [12] found detection rates for throat swab and CT scan of 59% and 88%, respectively. Taking RT-PCR result as a reference, chest CT showed sensitivity of 96.5%, specificity of 25.4%, positive predictive value of 65.3% and negative predictive value of 83.3%. CT performance seemed to be even slightly better among older patients (i.e. >60 years) and females.

An even lower sensitivity of RT-PCR testing was shown by LI et al. [13] in their retrospective analysis of 610 patients from Wuhan city with clinically and radiologically combined confirmation of COVID-19 diagnosis. In their cohort, only 39.5% cases had at least one positive RT-PCR result.

As for every laboratory test, real-time RT-PCR has intrinsic limitations that might significantly affect its accuracy in the diagnosis of COVID-19. False-negative results may depend on several pre-analytical and analytical vulnerabilities, such as inadequate procedures for specimen collection, handling, transport and storage; collection of inadequate material (quality or volume); sample contamination; execution of the test outside of the diagnostic window; use of nonvalidated assays; and many others [14] .

The combination of RT-PCR analytical vulnerability and major uncertainties about SARS-CoV-2 infection kinetics make it extremely difficult to accurately define the diagnostic window for the test itself, which becomes even harder to estimate on an individual basis rather than from an epidemiological point of view. Moreover, development of recombinant forms of SARS-CoV-2 may adversely affect the diagnostic accuracy of nucleic acid-based tests.

The source of respiratory specimen to be tested represents another critical issue. Collecting specimens at the right time from the right anatomic site seems crucial for laboratory diagnosis of SARS-CoV-2 infection through RT-PCR. WANG et al. [15] [16] , who also analysed the impact of time from symptom onset and disease severity on the detection rate of RT-PCR assays.

These data strongly encourage us to manage patients with a high pre-clinical likelihood (as everyone should be considered in those countries with high level of contagion) and typical clinical and radiological features as affected by COVID-19, independently of the result of real-time RT-PCR, especially if performed on specimens collected from the upper airways. Acquisition of lower respiratory tract samples should be always considered in the event of one or more negative RT-PCR assays, particularly in those

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2019-nCoV) in suspected human cases. Interim guidance. WHO REFERENCE NUMBER: WHO/COVID-19/laboratory/2020.5. www.who.int/ publications-detail/laboratory-testing-for-2019-novel-coronavirus-in-suspected-human-cases-20200117. Date last updated

European Centre for Disease Prevention and Control. Laboratory support for COVID-19 in the EU/EEA. www. ecdc.europa.eu/en/novel-coronavirus/laboratory-support. Date last updated: 15th

Interim Guidelines for Collecting, Handling, and Testing Clinical Specimens from Persons for Coronavirus Disease 2019 (COVID-19)

Use of chest CT in combination with negative RT-PCR assay for the 2019 novel coronavirus but high clinical suspicion

Negative nasopharyngeal and oropharyngeal swab does not rule out COVID-19

False-negative results of real-time reverse-transcriptase polymerase chain reaction for severe acute respiratory syndrome coronavirus 2: role of deep-learning-based CT diagnosis and insights from two cases

Computed tomographic imaging of 3 patients with coronavirus disease 2019 pneumonia with negative virus real-time reverse-transcription polymerase chain reaction test

A patient with COVID-19 presenting a false-negative reverse transcriptase polymerase chain reaction result

Sensitivity of chest CT for COVID-19: comparison to RT-PCR

Diagnosis of the coronavirus disease (COVID-19): rRT-PCR or CT?

Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases

Stability issues of RT-PCR testing of SARS-CoV-2 for hospitalized patients clinically diagnosed with COVID-19

Potential preanalytical and analytical vulnerabilities in the laboratory diagnosis of coronavirus disease 2019 (COVID-19)

Detection of SARS-CoV-2 in different types of clinical specimens

Evaluating the accuracy of different respiratory specimens in the laboratory diagnosis and monitoring the viral shedding of 2019-nCoV infections