Changes in serum virus-specific IgM/IgG antibody in asymptomatic and discharged patients with reoccurring positive COVID-19 nucleic acid test (RPNAT).

BACKGROUND: Studies have demonstrated the diagnostic efficiency of antibody testing in COVID-19 infection. There is limited data on the IgM/IgG changes in asymptomatic and discharged patients with reoccurring positive nucleic acid test (RPNAT). This study aims to investigate these IgM/IgG changes. METHODS: There were 111 patients with positive nucleic acid test (NAT) and 40 suspected patients enrolled in the study. The serum SARS-CoV-2 specific IgM/IgG antibody levels were retrospectively analysed with the disease progress in asymptomatic and RPNAT patients. RESULTS: The best overall performance was found by combining the IgM, IgG, and CT; 95.1% sensitivity and 75% specificity. This was tested in 111 RT-PCR positive cases. The median IgM and IgG levels were lower in the asymptomatic group compared to the symptomatic group (p < .01). Among 15 RPNAT cases, the IgM levels of the RPNAT group at the time of discharge (IgM2.79, IQR: 0.95-5.37) and retest (IgM 2.35, IQR: 0.88-8.65) were significantly higher than those of the non-reoccurring positive nucleic acid test group (Non-RPNAT) (IgM on discharge: 0.59, IQR: 0.33-1.22, IgG on retest: 0.92, IQR: 0.51-1.58). CONCLUSION: Serum SARS-CoV-2 specific IgM/IgG antibody levels remained at a low level during hospitalisation for asymptomatic patients. Elevated IgM levels may have implications in the identification of RPNAT patients before discharge. Key messages This study determined the IgM/IgG changes in asymptomatic and RPNAT patients. The rate of serum SARS-CoV-2 specific IgM/IgG antibody levels increase in the asymptomatic group was lower than in the symptomatic group during hospitalisation. The IgM level did not decrease significantly at discharge in the RPNAT patients, and was higher than that of the Non-RPNAT group on discharge. These results highlight the importance of timely monitoring of IgM levels to identify RPNAT patients before discharge.

A colloidal gold-based immunochromatographic strip for rapid detection of SARS-CoV-2 antibodies after vaccination.

Vaccination interventions is consideredan important preventive measure to block the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and protect the organism from pathogen infection effectively. However, a quick and accurate technique to evaluate the immune efficacy of the SARS-CoV-2 inactivated vaccine remains scarce. In this paper, an IgM-IgG antibody combined detection colloidal gold immunochromatography assay kit was optimized and developed, which can assess the efficacy of the inactivated SARS-CoV-2 vaccine. We collected fingertip blood samples from 3 vaccinees and 1 unvaccinated sample. The results showed that the proportion of antibody was high after the second shots immunization. The colloidal gold-based immunochromatographic strip is rapid, convenient and easy to operate. It can be used as an auxiliary method for preliminary evaluation of the antibody effect of vaccine recipients, and provide a reference index for the potential clinical application value of the vaccine.

Clinical validation of an immunochromatographic SARS-Cov-2 IgM/IgG antibody assay with Japanese cohort.

BACKGROUND: The coronavirus disease 2019 (COVID-19) has become a major health threat. To overcome COVID-19, appropriate diagnosis methods are urgently needed. The aim of this study was to clinically evaluate the colloidal gold immunochromatography assay for SARS-Cov-2 IgM/IgG antibody (Ab). METHODS: Patients confirmed COVID-19 (n = 51) were recruited prospectively from the Musashino Red Cross hospital and Tokyo Medical and Dental University Medical Hospital, between March and May 2020. And the analytical specificity was assessed with serum samples of patients without COVID-19 (n = 100) collected between August to September 2019 before SARS-CoV-2 was first reported in China. RESULTS: Among COVID-19 patients, a total of 87 serum samples were tested for SARS-Cov-2 IgM/IgG Ab assay. IgM was detected 71.0 %, 86.9 %, and 83.3 % at day8-14, 15-28, >29 after symptom onset and IgG was detected in 81.6 %, 87.0 %, and 94.4 %, respectively. The sensitivity of IgM and IgG Ab after day8 assay was significantly higher than before day7, respectively (p=0.0016, 0.0003). There were no positive results in 100 serum samples from patients without COVID-19. CONCLUSION: The SARS-Cov-2 IgM/IgG Ab assay had 79.7% / 86.1% sensitivity (the 8 days after from onset) and 100% specificity in this population.

Analysis of adjunctive serological detection to nucleic acid test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection diagnosis.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused coronavirus disease 2019 (COVID-19) epidemic in China, December 2019. The clinical features and treatment of COVID-19 patients remain largely elusive. However, accurate detection is required for SARS-CoV-2 infection diagnosis. We aimed to evaluate the antibodies-based test and nucleic acid-based test for SARS-CoV-2-infected patients. METHODS: We retrospectively studied 133 patients diagnosed with SARS-CoV-2 and admitted to Renmin Hospital of Wuhan University, China, from January 23 to March 1, 2020. Demographic data, clinical records, laboratory tests, and outcomes were collected. Data were accessed by SARS-CoV-2 IgM-IgG antibody test and real-time reverse transcriptase PCR (RT-PCR) detection for SARS-CoV-2 nucleic acid in COVID-19 patients. RESULTS: Of 133 COVID-19 patients, there were 44 moderate cases, 52 severe cases, and 37 critical cases with no differences in gender and age among three subgroups. In RT-PCR detection, the positive rate was 65.9%, 71.2%, and 67.6% in moderate, severe, and critical cases, respectively. Whereas the positive rate of IgM/IgG antibody detection in patients was 79.5%/93.2%, 82.7%/100%, and 73.0%/97.3% in moderate, severe, and critical cases, respectively. Moreover, the IgM and IgG antibodies concentrations were also examined with no differences among three subgroups. CONCLUSION: The IgM-IgG antibody test exhibited a useful adjunct to RT-PCR detection, and improved the accuracy in COVID-19 diagnosis regardless of the severity of illness, which provides an effective complement to the false-negative results from a nucleic acid test for SARS-CoV-2 infection diagnosis after onsets.