ABSTRACT
The immense patient number caused by coronavirus disease 2019 (COVID-19) global pandemic brings the urge for more knowledge about its immunological features, including the profile of basic immune parameters. In this study, eighty-eight reported COVID-19 patients in Wuhan were recruited from January to February, 2020, including 32 severe/critical cases and 56 mild/moderate cases. Their mean age was 56.43 years (range 17-83) and gender ratio (male/female) was 43:45. We tested SARS-CoV-2 RNA with commercial kits, investigated the level of serologic IgM and IgG antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using magnetic particle chemiluminescence immunoassays, and compared the results of serologic tests and nucleic acid test (NAT). Among 88 patients, 95.45% were confirmed as positive by the combination of NAT and antibody test, which was significantly higher (P < 0.001) than by single nucleic acid test (73.86%) or serologic test (65.91%). Then the correlation between temporal profile and the level of antibody response was analyzed. It showed that seroconversion started on day 5 after disease onset and IgG level was rose earlier than IgM. Comparison between patients with different disease severity suggested early seroconversion and high antibody titer were linked with less severe clinical symptoms. These results supported the combination of serologic testing and NAT in routine COVID-19 diagnosis and provided evidence on the temporal profile of antibody response in patients with different disease severity.
Subject(s)
COVID-19 Serological Testing/methods , COVID-19/immunology , COVID-19/virology , SARS-CoV-2/immunology , Adolescent , Adult , Aged , Aged, 80 and over , Antibodies, Viral/immunology , Antibody Formation , COVID-19/blood , COVID-19/epidemiology , COVID-19 Nucleic Acid Testing/methods , China/epidemiology , Female , Humans , Immunoglobulin G/blood , Immunoglobulin G/immunology , Immunoglobulin M/blood , Immunoglobulin M/immunology , Luminescent Measurements/methods , Male , Middle Aged , Pandemics , Real-Time Polymerase Chain Reaction/methods , SARS-CoV-2/genetics , Young AdultABSTRACT
The outbreak of COVID-19 caused by a novel Coronavirus (termed SARS-CoV-2) has spread to over 210 countries around the world. Currently, reverse transcription quantitative qPCR (RT-qPCR) is used as the gold standard for diagnosis of SARS-CoV-2. However, the sensitivity of RT-qPCR assays of pharyngeal swab samples are reported to vary from 30% to 60%. More accurate and sensitive methods are urgently needed to support the quality assurance of the RT-qPCR or as an alternative diagnostic approach. A reverse transcription digital PCR (RT-dPCR) method was established and evaluated. To explore the feasibility of RT-dPCR in diagnostic of SARS-CoV-2, a total of 196 clinical pharyngeal swab samples from 103 suspected patients, 77 close contacts and 16 supposed convalescents were analyzed by RT-qPCR and then measured by the proposed RT-dPCR. For the 103 fever suspected patients, 19 (19/25) negative and 42 (42/49) equivocal tested by RT-qPCR were positive according to RT-dPCR. The sensitivity of SARS-CoV-2 detection was significantly improved from 28.2% by RT-qPCR to 87.4% by RT-dPCR. For 29 close contacts (confirmed by additional sample and clinical follow up), 16 (16/17) equivocal and 1 negative tested by RT-qPCR were positive according to RT-dPCR, which is implying that the RT-qPCR is missing a lot of asymptomatic patients. The overall sensitivity, specificity and diagnostic accuracy of RT-dPCR were 91%, 100% and 93%, respectively. RT-dPCR is highly accurate method and suitable for detection of pharyngeal swab samples from COVID-19 suspected patients and patients under isolation and observation who may not be exhibiting clinical symptoms.