Analysis of rapid and molecular SARS-CoV-2 tests in patients with mild COVID-19

Abstract

Introduction: With real-time polymerase chain reaction (RT-PCR), the viral RNA of the new coronavirus is detected within the first three weeks of infection. Immunological tests detect IgM and IgG immunoglobulins against SARS-CoV-2, which usually appear since the second week of infection.

Objective: To describe the results of RT-PCR in outpatients and hospitalized patients with two or more IgM results by immunochromatography, without detection of IgG+ and with COVID-19.

Methods: Outpatients and hospitalized patients with two or more anti–SARS-CoV-2 IgM antibody results were selected, with no evidence of positive IgG. A total of 42 people were evaluated, nineteen of them were health professionals (outpatients) and 23 were hospitalized patients.

Results: Only seven people tested positive for SARS-CoV-2 by RT-PCR. Of those with symptoms, only two, out of eleven, tested positive for the molecular test, a results similar to that of asymptomatic patients who tested positive for the molecular test (five out of 21). Of the immunosuppressed patients, three patients had a positive RT-PCR result (two were cancer patients and one was HIV-positive). Of the patients who were negative by RT-PCR, six patients were cancer patients and two had diabetes.

Conclusions: SARS-CoV-2 detection by RT-PCR in immunocompromised patients should be done regardless of the presence of antibodies or symptoms, since they will not benefit from rapid tests due to their misdiagnosis. The presence of positive anti–SARS-CoV-2 IgM or positive RT-PCR should not be interpreted as an active infection in the patient; two tests of this nature with a difference greater than seven days usually coincide with the time in which the virus loses viability. To determine active infection, other patterns such as clinical and laboratory response should be assessed.