The objective of the present study was to evaluate the true positivity among people, whose results of initial testing of nasopharyngeal swabs (NPS) showed a very low viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Seventy-seven people detected with low viral loads of SARs-CoV-2 in nasopharyngeal samples (Ct ≥ 35) were enrolled in the study. For this purpose, a second NPS was collected for rRT-PCR (real-time reverse transcription polymerase chain reaction) combined with a pair of serum samples for detection of anti-nucleocapsid (anti-N) and anti-spike (anti-S) antibodies. In 8 people, subsequent examinations indicated an increase in viral loads, thereafter, followed by an increase of anti-N and anti-S antibodies, findings compatible with an early stage of COVID-19 infection. In 9 people, who already had increased anti-N antibodies, subsequent examination showed a decrease or absence of viral load and an increase in antibodies, indicative of a late stage of COVID-19 infection. In 60 people, subsequent examination showed absence of infection (as indicated by absence of viral load and antibodies). We propose that the combination of a second NPS and one serum-specimen, both taken three days after the first NPS, helps significantly to avoid false-positive results.
【저자키워드】 COVID-19, Diagnosis, Greece, N gene, False positive, anti-spike antibodies, Anti-nucleocapsid antibodies, low viral load, 【초록키워드】 antibodies, SARS-CoV-2, coronavirus, Infection, Nasopharyngeal swab, rRT-PCR, COVID-19 infection, Viral load, anti-N antibodies, reverse transcription, early stage, Anti-spike, Combination, False-positive results, acute respiratory syndrome, viral loads, help, late stage, anti-S, serum sample, nasopharyngeal sample, NPs, decrease, polymerase chain, initial, enrolled, evaluate, significantly, indicated, subsequent, was collected, absence, increase in, 【제목키워드】 rRT-PCR, experience,