ABSTRACT
BACKGROUND: COVID-19 has become a global pandemic, and close contacts and asymptomatic patients are worthy of attention. METHODS: A total of 1844 people in close contacts with 76 COVID-19 patients were investigated, and nasopharyngeal swabs and venous blood were collected for centralized medical quarantine observation. Real-time fluorescence was used to detect SARS-CoV-2 nucleic acid in nasopharyngeal swabs of all close contacts, and the colloidal gold method was used to detect serum-specific antibodies. Levels of IgM- and IgG-specific antibodies were detected quantitatively through chemiluminescence from the first nucleic acid turned negative date (0 week) and on weekly intervals of ≤1 week, 1-2 weeks, 2-3 weeks, 3-4 weeks, 4-5 weeks, 5-6 weeks, and 6-7 weeks. RESULTS: The total positive rate of the colloidal gold method (88.5%, 23/26) was significantly higher (χ2 = 59.182, p < 0.001) than that of the healthy control group (2.0%, 1/50). There was significant difference in IgG concentration at different time points (0-7 weeks) after negative nucleic acid conversion (χ2 = 14.034, p = 0.029). Serum IgG levels were significantly higher at weekly time points of 4-5 weeks (Z = -2.399, p = 0.016), 5-6 weeks (Z = -2.049, p = 0.040), and 6-7 weeks (Z = -2.197, p = 0.028) compared with 1-2 weeks after negative nucleic acid conversion. However, there was no significant difference (χ2 = 4.936, p = 0.552) in IgM concentration between time points tested (0-7 weeks) after negative nucleic acid conversion. The positive rates of IgM and IgG in asymptomatic patients (χ2 = 84.660, p < 0.001) were significantly higher than those in the healthy control group (χ2 = 9.201, p = 0.002) within 7 weeks of negative nucleic acid conversion. CONCLUSIONS: The IgG concentration in asymptomatic cases remained at a high level after nucleic acid turned negative. Nucleic acid detection combined with IgM and IgG antibody detection is an effective way to screen asymptomatic infections.
Subject(s)
COVID-19 Serological Testing/methods , Immunoglobulin G/blood , Immunoglobulin M/blood , Adult , Aged , COVID-19/epidemiology , Carrier State/blood , China/epidemiology , Female , Gold Colloid , Humans , Male , Middle AgedABSTRACT
BACKGROUND AND PURPOSE: Studies have shown that some cytokines in COVID-19 patients were elevated. This study aims to assess whether IL-10, IL-1ß, IL-6, MCP-1, TNF-α, IP-10 and IL-4 serve as potential diagnostic biomarkers of COVID-19. METHODS: The above serum cytokines in COVID-19 patients and non-COVID-19 patients were detected by ELISA and SARS-CoV-2 IgM and IgG were detected by the chemiluminescence method. The independent-sample Mann-Whitney U test was utilised to compare cytokine levels in different groups and courses, the Levene T-test and T'-test were utilised to compare they in different genders and the Spearman correlation test was utilised to analyse the correlation between the cytokine levels with ages and SARS-CoV-2 IgG and IgM. RESULTS: Serum levels of IL-10, IL-1ß, MCP-1, TNF-α and IL-4 in COVID-19 patients were significantly higher than those in non-COVID-19 patients, while IL-6 were only significantly higher than in healthy people, IP-10 were significantly lower than in other diseases patients. AUCs of COVID-19 diagnosed by IL-10, IL-1ß, IL-6, MCP-1, TNF-α, IP-10 and IL-4 were 0.735, 0.775, 0.595, 0.821, 0.848, 0.38 and 0.682, respectively. In the COVID-19 patients' serum, the levels of IL-10 and MCP-1 of male were noticeably higher than those of female, and all cytokines were significantly positively correlated with age, IL-1ß and IL-4 were significantly negatively correlated with SARS-CoV-2 IgM, while IL-10, IL-1ß, IL-6, TNF- and IP-10 were significantly negatively correlated with SARS-CoV-2 IgG. IL-10 on 43-56 days was significantly lower than at 29-42 days, TNF-α at 15-42 days was significantly higher than at 0-14 days, IP-10 at 0-14 days was the highest and IL-4 at 29-42 days was significantly higher than at 0-14 days. CONCLUSIONS: The detection of IL-10, IL-1 ß, IL-6, MCP-1, TNF-α and IL-4 would assist the clinical study of COVID-19, and IP-10 may be the cytokine of early elevation in COVID-19 patients.