key: cord-0944379-umthoftd
authors: Jia, Xingwang; Xiao, Liehui; Liu, Yajie
title: False Negative RT-PCR and False Positive Antibody Tests ——Concern and Solutions in the Diagnosis of COVID-19
date: 2020-10-08
journal: J Infect
DOI: 10.1016/j.jinf.2020.10.007
sha: d33a04e36cad76fb613dd14a44778b02cc595eb8
doc_id: 944379
cord_uid: umthoftd

nan

Sir,

We read with interest that antibody testing using a rapid immunochromatographic assay is reliable in the diagnosis of severe acute respiratory syndrome coronavirus 2 ( SARS-CoV-2 ) infection 1 . However, the accuracy of antibody testing and RT-PCR does not meet the need for a large number of screening tests. False negative RT-PCR and false positive antibody tests are a concern.

Coronavirus disease 2019 (COVID-19), which is caused by SARS-Cov-2, was first detected at the end of 2019, and was named by the World Health Organization on January 12, 2020. COVID-19 is now a pandemic. It took only 25 days for newly confirmed cases to decrease to zero in Beijing in June, which revealed that timely discovery, accurate diagnosis, early isolation and treatment of COVID-19 are the most effective measures. positive antibody results could be eliminated after five times dilution with normal human serum, when the RF level was lower than 10 IU/mL. It was not eliminated after five times dilution with physiological saline [Fig. 1 ]. We also identified five patients with false antibody results, who had nasopharyngeal carcinoma, colon cancer, duodenal carcinoma, diabetes, and diffuse bronchitis, respectively. Serum RF level in these patients was lower than 100 IU/mL. The false positive antibody results could also be eliminated after 5 times dilution with normal human serum. Thus, further studies are needed to investigate the false results of this test. 4 We believe that no diagnostic technique has 100% sensitivity and specificity.

Although the RT-PCR test has become the standard method for the diagnosis of SARS-CoV-2 infection, false-negative rates have been reported. For the serological antibody test, the detection time needs to consider the window period. Moreover, several factors should be considered when diagnosing COVID-19, including epidemiology, history of exposure and clinical symptoms, such as fever or respiratory disease.

Therefore, the combination of serum IgM/IgG antibody detection, the nucleic acid test, CT scan and clinical features improves the accuracy of COVID-19 diagnosis.

This study was approved by the Ethics Committee of Shenzhen Hospital, Southern Medical University (NYSZYYEC20200009).

The authors declare that they have no conflict of interest. 

Reliability and usefulness of a rapid IgM-IgG antibody test for the diagnosis of SARS-CoV-2 infection: A preliminary report

False Negative Tests for SARS-CoV-2 Infection -Challenges and Implications

Detection of SARS-CoV-2 in Different Types of Clinical Specimens

Potential False-Negative Nucleic Acid Testing Results for Severe Acute Respiratory Syndrome Coronavirus 2 from Thermal Inactivation of Samples with Low Viral Loads

Clinical significance of IgM and IgG test for diagnosis of highly suspected COVID-19 infection

Humoral Immune Response to SARS-CoV-2 in Iceland

Cross-reaction of SARS-CoV antigen with autoantibodies in autoimmune diseases

We thank Lijun Zhang and Qing Liu of the Department of Clinical Laboratory Medicine Center, Shenzhen Hospital, Southern Medical University who collected the serum samples.