Are RNA-Based Tests Sufficient for COVID-19 Diagnosis? An Inspiration of Three Asymptomatic Cases

Abstract

In this work, we discovered a new phenomenon-asymptomatic COVID-19 infection, or covert case, during the pandemic. All the 3 patients had a history of exposure, with no symptoms, and no abnormalities were found in computed tomography scan or lab tests. Except for case 2, the other patients' severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) nucleic acid tests were negative. But their anti-SARS-COV-2 nucleocapsid antibody showed a dynamic trend, consistent with the process of virus infection and clearance. A growing number of asymptomatic or covert cases need more attention. Lack of surveillance may lead to another outbreak. We hope to demonstrate our cases to attract the attention of governments or health authorities that covert cases should be the focus as well.

Keywords: COVID-19; PCR-negative; asymptomatic; diagnosis.

Figure 1.

The outcomes of coronavirus disease 2019 (COVID-19) infection. The disease can be divided into 3 stages: Stage I, severe acute respiratory syndrome coronavirus 2infection with no symptoms, clinically will last for 2 weeks as the incubation period. Stage II, the virus colonized in the respiratory tract through droplets, aerosol, etc. With the increase in the viral load, some people show symptoms such as fever, cough, fatigue, myalgia, etc., who then COVID-19 diagnosis is confirmed by a positive nucleic acid polymerase chain reaction (PCR) test. Their condition maybe mild (need no treatment), moderate (need a hospital care), and severe or even critical (need an intensive care unit care). Another group of people also confirmed by a positive nucleic acid PCR test with no symptoms called covert cases. Stage III, the immune system may produce antibody during the process of virus’s elimination. The titer of immunoglobulin (Ig)G increased, while IgM decreased during the convalescent period.

Figure 2.

Timeline of lab test of covert cases.