The risk for celiac disease after Covid-19 infection.

BACKGROUND: Celiac disease (CD) is an autoimmune disease leading to gastrointestinal symptoms and mineral deficiencies. The pathogenetic mechanisms, besides the clear HLA association, are elusive. Among environmental factors infections have been proposed. Covid-19 infection results in a systemic inflammatory response that often also involves the gastrointestinal tract. The aim of the present study was to investigate whether Covid-19 infection could increase the risk for CD. PATIENTS AND METHODS: All patients, both children and adults, in the county Skåne (1.4 million citizens) in southern Sweden with newly diagnosed biopsy- or serology-verified CD or a positive tissue transglutaminase antibody test (tTG-ab) during 2016-2021 were identified from registries at the Departments of Pathology and Immunology, respectively. Patients with a positive Covid-19 PCR or antigen test in 2020 and 2021 were identified from the Public Health Agency of Sweden. RESULTS: During the Covid-19 pandemic (March 2020 - December 2021), there were 201 050 cases of Covid-19 and 568 patients with biopsy- or serology-verified CD or a first-time positive tTG-ab tests, of which 35 patients had been infected with Covid-19 before CD. The incidence of verified CD and tTG-ab positivity was lower in comparison to before the pandemic (May 2018 - February 2020; 22.5 vs. 25.5 cases per 100 000 person-years, respectively, incidence rate difference (IRD) -3.0, 95% CI -5.7 - -0.3, p = 0.028). The incidence of verified CD and tTG-ab positivity in patients with and without prior Covid-19 infection was 21.1 and 22.4 cases per 100 000 person-years, respectively (IRD - 1.3, 95% CI -8.5-5.9, p = 0.75). CONCLUSIONS: Our results indicate that Covid-19 is not a risk factor for CD development. While gastrointestinal infections seem to be an important part of the CD pathogenesis, respiratory infections probably are of less relevance.

Systematic evaluation of SARS-CoV-2 antigens enables a highly specific and sensitive multiplex serological COVID-19 assay.

OBJECTIVE: The COVID-19 pandemic poses an immense need for accurate, sensitive and high-throughput clinical tests, and serological assays are needed for both overarching epidemiological studies and evaluating vaccines. Here, we present the development and validation of a high-throughput multiplex bead-based serological assay. METHODS: More than 100 representations of SARS-CoV-2 proteins were included for initial evaluation, including antigens produced in bacterial and mammalian hosts as well as synthetic peptides. The five best-performing antigens, three representing the spike glycoprotein and two representing the nucleocapsid protein, were further evaluated for detection of IgG antibodies in samples from 331 COVID-19 patients and convalescents, and in 2090 negative controls sampled before 2020. RESULTS: Three antigens were finally selected, represented by a soluble trimeric form and the S1-domain of the spike glycoprotein as well as by the C-terminal domain of the nucleocapsid. The sensitivity for these three antigens individually was found to be 99.7%, 99.1% and 99.7%, and the specificity was found to be 98.1%, 98.7% and 95.7%. The best assay performance was although achieved when utilising two antigens in combination, enabling a sensitivity of up to 99.7% combined with a specificity of 100%. Requiring any two of the three antigens resulted in a sensitivity of 99.7% and a specificity of 99.4%. CONCLUSION: These observations demonstrate that a serological test based on a combination of several SARS-CoV-2 antigens enables a highly specific and sensitive multiplex serological COVID-19 assay.

Rapid diagnostic testing for SARS-CoV-2: Validation and comparison of three point-of-care antibody tests.

With the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a need for diagnostic tests has surfaced. Point-of-care (POC) antibody tests can detect immunoglobulin (Ig) G and M against SARS-CoV-2 in serum, plasma, or whole blood and give results within 15 min. Validation of the performance of such tests is needed if they are to be used in clinical practice. In this study, we evaluated three POC antibody tests. Convalescent serum samples from 47 reverse transcription-polymerase chain reaction (RT-PCR) verified patients with coronavirus disease 2019 (COVID-19) collected at least 28 days post RT-PCR diagnosis as well as 50 negative pre-COVID-19 controls were tested. The three tests (denoted the J-, N-, and Z-tests) displayed the sensitivities of 87%, 96%, and 85%, respectively, for the detection of IgG. All tests had the same specificity for IgG (98%). The tests did not differ significantly for the detection of IgG. The sensitivities for IgM were lower (15%, 67%, and 70%) and the specificities were 90%, 98%, and 90%, respectively. The positive and negative predictive values were similar among the tests. Our results indicate that these POC antibody tests might be accurate enough to use in routine clinical practice.