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BackgroundEvaluating the performance of SARS-CoV-2 serological assays and clearly articulating the utility of selected antigen, isotypes and thresholds is crucial to understanding the prevalence of infection within selected communities. MethodsThis cross-sectional study, implemented in 2020, screened PCR-confirmed COVID-19 patients (n=86), banked pre-pandemic and negative donors (n=96), health care workers and family members (n=552), and university employees (n=327) for anti-SARS-CoV-2 receptor-binding domain (RBD), trimeric spike protein (S), and nucleocapsid protein (N) IgG and IgA antibodies with a laboratory developed Enzyme-Linked Immunosorbent Assay (ELISA) and tested how antigen, isotype and threshold choices affected the seroprevalence. The following threshold methods were evaluated: (i) mean + 3 standard deviations of the negative controls; (ii) 100% specificity for each antigen/isotype combination; and (iii) the maximal Youden index. ResultsWe found vastly different seroprevalence estimates depending on selected antigens, isotypes and the applied threshold method, ranging from 0.0% to 85.4%. Subsequently, we maximized specificity and reported a seroprevalence, based on more than one antigen, ranging from 9.3% to 25.9%. ConclusionsThis study revealed the importance of evaluating serosurvey tools for antigen, isotype, and threshold-specific sensitivity and specificity, in order to interpret qualitative serosurvey outcomes reliably and consistently across studies.
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Aim To investigate the effects of maternal chronic aluminum exposure on memorial behaviour and hippocampal intracellular Ca2+ concentration ([Ca2+]i)on their offspring after the induction of LTP(long-term potentiation). Methods Adult Wistar rats (150~200 g) were exposed to aluminum by drinking distilled water, the concentration of AlCl3 is 0.015 mol?L-1(2 g?L-1) and 0.03 mol?L-1(4 g?L-1) aluminum chloride (AlCl3) solution, respectively, for 30 days prior to mating and during the whole gestation and suckling period. Their offspring were distributed into three experimental groups: control group; two exposed groups (represented by 0.2%-Al and 0.4%-Al ) administrated aluminum exposure ended at postnatal day 21. The brain tissue and blood aluminum levels were measured by Atomic absorption spectrometry (AAS). Memorial ability of the offspring was tested by Step down test.[Ca2+]i was measured by the technique of Fura-2/AM calcium ions fluorescence indicator. Results The mean aluminum content in blood and brain tissue was significantly higher than the control group(P0.05), but was significantly decreased in 0.4%-Al exposed group(P