Purpose
Antibody assays against SARS-CoV-2 are used in sero-epidemiological studies to estimate the proportion of a population with past infection. IgG antibodies against the spike protein (S-IgG) allow no distinction between infection and vaccination. We evaluated the role of anti-nucleocapsid-IgG (N-IgG) to identify individuals with infection more than one year past infection.
Methods
S- and N-IgG were determined using the Euroimmun enzyme-linked immunosorbent assay (ELISA) in two groups: a randomly selected sample from the population of Stuttgart, Germany, and individuals with PCR-proven SARS-CoV-2 infection. Participants were five years or older. Demographics and comorbidities were registered from participants above 17 years.
Results
Between June 15, 2021 and July 14, 2021, 454 individuals from the random sample participated, as well as 217 individuals with past SARS-CoV-2 infection. Mean time from positive PCR test result to antibody testing was 458.7 days (standard deviation 14.6 days) in the past infection group. In unvaccinated individuals, the seroconversion rate for S-IgG was 25.5% in the random sample and 75% in the past infection group (P = < 0.001). In vaccinated individuals, the mean signal ratios for S-IgG were higher in individuals with prior infection (6.9 vs 11.2; P = < 0.001). N-IgG were only detectable in 17.1% of participants with past infection. Predictors for detectable N-IgG were older age, male sex, fever, wheezing and in-hospital treatment for COVID-19 and cardiovascular comorbidities.
Conclusion
N-IgG is not a reliable marker for SARS-CoV-2 infection after more than one year. In future, other diagnostic tests are needed to identify individuals with past natural infection.
Uzara glycosides (UG) extracted from Xysmalobium undulatum are used for treating non-specific diarrhea.Cross-reactivity has been described for UG in digitalis glycoside assays but digitalis-like cardiac effects are controversially discussed. Therefore, we performed a randomized, singleblind cross-over study in 18 healthy volunteers receiving a commercially available Uzara product (Uzara® Lösung N, Stada AG, Bad Vilbel, Germany (ULN)), digoxin (1 mg, i.v., positive control) and placebo in double-dummy technique. Pharmacodynamic effects were quantified by means of ECG and impedance cardiography (ICG). After oral administration of ULN, main metabolites were determined using HPLC-MS/MS and digitalis-like serum levels (DLSL) were measured in two digitoxin and digoxin assays, respectively. In comparison to placebo, ULN did not change significantly any PD parameters whereas digoxin altered significantly area under the effect curve of several ECG and ICG parameters, respectively. Since some serum levels of three ULN ingredients (uzarin, uzarigenin and xysmalorin) were below LLQ, PK analyses could only be performed for allouzarigenin and revealed a marked inter-individual variability. Therefore, median values (min; max) were calculated as follows: Cmax = 0.39 (0.15; 1.81) ng/ml, tmax = 7.0 (3.0; 36.0) h, T1/2 = 5.2 (0.8; 23.6) h, AUC0-36h = 4.2 (0.8; 11.1) ng/ml×h, AUC0-∞ = 5.8 (1.8; 13.1) ng/ml×h. DLSL reached Cmax of 28 ng/ml and 1,980 ng/ml for digoxin and digitoxin, respectively. We could not observe significant cardiovascular pharmacodynamic effects after oral administration of the recommended single dose of Uzara extract to healthy volunteers. However, considerable DLSL could be detected, proving cross-reactivity of uzara components with the conventional digitalis assays used. However, none of the metabolites we had suspected to be the cause for the crossreactivity could be identified in reasonable quantities.
Background
:
Universal admission screening for SARS-CoV-2 in children and their caregivers (CG) is critical to prevent hospital outbreaks. We evaluated pooled SARS-CoV-2 antigen tests (AG) to identify infectious individuals while waiting for PCR test results.
Methods
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This single-center study was performed from November 5, 2020 to March 1, 2021. Nasal mid-turbinate and oropharyngeal swabbing for AG and PCR testing was performed in children with two individual swabs that were simultaneously inserted. Nasopharyngeal swabs were obtained from their CG. AG swabs were pooled in a single extraction buffer tube and PCR swabs in a single viral medium. Results from an adult population were used for comparison, as no pooled testing was performed.
Findings
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During the study period, 710 asymptomatic children and their CG were admitted. Pooled AG sensitivity and specificity was 75% and 99.4% respectively for detection of infectious individuals. Four false negatives were observed, though three out of four false negative child-CG pairs were not considered infectious at admission. Unpooled AG testing in an adult population showed a comparable sensitivity and specificity of 50% and 99.7%. AG performed significantly better in samples with lower Ct values in the corresponding PCR (32.3 vs 21, p-value <0.001).
Conclusions
:
Pooled SARS-CoV-2 AGs are an effective method to identify potentially contagious individuals prior admission, without adding additional strain to the child.
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