Sex-specific differences in physiological parameters related to SARS-CoV-2 infections among a national cohort (COVI-GAPP study) (preprint)

Considering sex as a biological variable in modern digital health solutions, we investigated sex-specific differences in the trajectory of four physiological parameters across a COVID-19 infection. A wearable medical device measured breathing rate, heart rate, heart rate variability, and wrist skin temperature in 1163 participants (mean age = 44.1 years, standard deviation [SD]=5.6; 667 [57%] females). Participants reported daily symptoms and confounders in a complementary app. A machine learning algorithm retrospectively ingested daily biophysical parameters to detect COVID-19 infections. COVID-19 serology samples were collected from all participants at baseline and follow-up. We analysed potential sex-specific differences in physiology and antibody titres using multilevel modelling and t-tests. Over 1.5 million hours of physiological data were recorded. During the symptomatic period of infection, men demonstrated larger increases in skin temperature, breathing rate and heart rate as well as larger decreases in heart rate variability than women. The COVID-19 infection detection algorithm performed similarly well for men and women. Our study belongs to the first research to provide evidence for differential physiological responses to COVID-19 between females and males, highlighting the potential of wearable technology to inform future precision medicine approaches. This work has received support from the Princely House of the Principality of Liechtenstein, the government of the Principality of Liechtenstein, the Hanela Foundation in Switzerland, and the Innovative Medicines Initiative (IMI) 2 Joint Undertaking under grant agreement No 101005177. This Joint Undertaking receives support from the European Union's Horizon 2020 research and innovation programme and EFPIA.

How much should we sequence? An analysis of the Swiss SARS- CoV-2 surveillance effort (preprint)

Background During the SARS-CoV-2 pandemic, many countries directed substantial resources towards genomic surveillance to detect and track viral variants. There is a debate over how much sequencing effort is necessary in national surveillance programs for SARS-CoV-2 and future pandemic threats. Aim We aimed to investigate the effect of reduced sequencing on surveillance outcomes in a large genomic dataset from Switzerland, comprising more than 143k sequences. Methods We employed a uniform downsampling strategy using 100 iterations each to investigate the effects of fewer available sequences on the surveillance outcomes: (i) first detection of variants of concern (VOCs), (ii) speed of introduction of VOCs, (iii) diversity of lineages, (iv) first cluster detection of VOCs, (v) density of active clusters, and (vi) geographic spread of clusters. Results The impact of downsampling on VOC detection is disparate for the three VOC lineages , but many outcomes including introduction and cluster detection could be recapitulated even with only 35% of the original sequencing effort. The effect on the observed speed of introduction and first detection of clusters was more sensitive to reduced sequencing effort for some VOCs, in particular Omicron and Delta, respectively. Conclusion A genomic surveillance program needs a balance between societal benefits and costs. While the overall national dynamics of the pandemic could be recapitulated by a reduced sequencing effort, the effect is strongly lineage dependent - something that is unknown at the time of sequencing - and comes at the cost of accuracy, in particular for tracking the emergence of potential VOCs.

The role of serum brain injury biomarkers in individuals with a mild-to-moderate COVID infection and Long-COVID - results from the prospective population-based COVI-GAPP study (preprint)

Background: During and after mild (no hospitalization) or moderate (hospitalization without ICU) SARS-CoV-2 infections, a wide range of symptoms, including neurological disorders have been reported. It is, however, unknown if these neurological symptoms are associated with brain injury and whether brain injury and related symptoms also emerge in patients suffering from Long-COVID. Neuronal biomarkers such as serum neurofilament light chain and glial fibrillary acidic protein can be used to elucidate neuro-axonal and astroglial injuries. We therefore investigated whether these biomarkers are associated with the COVID-19 infection status (mild-to-moderate), the associated symptoms and Long-COVID. Methods: From 146 individuals of the general population with a post-acute, mild-to-moderate SARS-CoV-2 infection, serum neurofilament light chain (sNfL; marker of intra-axonal neuronal injury) and serum glial fibrillary acidic protein (sGFAP; marker of astrocytic activation/injury) were measured. Samples were taken before, during and after (five and ten months) a SARS-CoV-2 infection. Individual symptoms and Long-COVID status were assessed using questionnaires. Results: Neurological symptoms were described for individuals after a mild and moderate COVID-19 infection, however, serum markers of brain injury (sNfL/sGFAP) did not change after an infection (sNfL: P = 0.74; sGFAP: P = 0.24) and were not associated with headache (P = 0.51), fatigue (P = 0.93), anosmia (P = 0.77) and ageusia (P = 0.47). In participants with Long-COVID, sGFAP (P = 0.038), but not sNfL (P = 0.58) significantly increased but was not associated with neurological symptoms. Conclusion: Neurological symptoms in individuals after a mild-to-moderate SARS-CoV-2 infection with and without Long-COVID were not associated with brain injury, although there was some astroglial injury observed in Long-COVID patients. Funding: The COVI-GAPP study received grants from the Innovative Medicines Initiative (IMI grant agreement number 101005177), the Princely House of Liechtenstein, the government of the Principality of Liechtenstein, and the Hanela Foundation (Switzerland). None of the funders played a role in the study design, data collection, data analysis, data interpretation, writing of the report, or decision to publish.

Association of viral variant and vaccination status with the occurrence of symptoms compatible with post-acute sequelae after primary SARS-CoV-2 infection (preprint)

Importance: Disentangling the effects of different SARS-CoV-2 variants and of vaccination on the occurrence of post-acute sequelae of SARS-CoV-2 (PASC) is crucial to estimate and potentially reduce the future burden of PASC. Objective: To determine the association of primary SARS-CoV-2 infection on the frequency of PASC symptoms by viral variant and vaccination status. Design: Cross-sectional questionnaire and SARS-CoV-2 serology (May/June 2022) performed within a prospective healthcare worker cohort (SURPRISE study). Setting: Multicenter study in nine healthcare networks from North-Eastern Switzerland. Participants: Volunteer sample of healthcare workers (HCW) from participating institutions. Of approximately 20000 eligible participants, 3870 registered for the cohort and 2912 were included in this analysis. Exposures: SARS-CoV-2 infection documented by positive nasopharyngeal swab (>4 weeks ago), stratified by viral variant and vaccination status at time of infection, compared to absence of documented infection (no positive swab, negative serology). Main Outcome: Sum score of eighteen self-reported PASC symptoms. Results: Among 2912 participants (median age 44 years, 81.3% female), SARS-CoV-2 infection was reported by 1685 (55.9%) participants, thereof 315 (18.7%) during Wild-type, 288 (17.1%) during Alpha/Delta, and 1082 (64.2%) during Omicron circulation. Mean symptom number in previously infected participants significantly exceeded that of uninfected controls (0.39), but decreased with recency of the viral variant: 1.12 (p<0.001) for Wild-type (median time since infection 18.5 months), 0.67 (p<0.001) for Alpha/Delta (6.6 months), and 0.52 (p=0.005) for Omicron BA.1 (3.1 months) infected participants. After Omicron BA.1 infection, the mean symptom score was 0.49 (p=0.30) for those with at least 3 prior vaccinations and 0.71 (p=0.028) with 1-2 previous vaccinations compared to 0.36 for unvaccinated individuals. Adjusting for confounders, Wild-type (adjusted risk ratio [aRR] 2.81, 95% confidence interval [CI] 2.08-3.83) and Alpha/Delta infection (aRR 1.93, 95% CI 1.10-3.46) showed significant associations with the outcome, whereas Omicron BA.1 infection (aRR 1.29, 95% CI 0.69-2.43) and vaccination before infection (aRR 1.27, 95% CI 0.82-1.94) did not. Conclusions and Relevance: Previous infection with pre-Omicron variants was the strongest risk factor for reporting PASC symptoms in this HCW cohort. A definite influence of prior vaccination on the prevention of PASC after Omicron BA.1 infection was not measurable.

Symptoms compatible with long-COVID in healthcare workers with and without SARS-CoV-2 infection - results of a prospective multicenter cohort (preprint)

Background: The burden of long-term symptoms (i.e. long-COVID) in patients after mild COVID-19 is debated. Within a cohort of healthcare workers (HCW), frequency and risk factors for symptoms compatible with long-COVID are assessed. Methods: Participants answered baseline (August/September 2020) and weekly questionnaires on SARS-CoV-2 nasopharyngeal swab (NPS) results and acute disease symptoms. In January 2021, SARS-CoV-2 serology was performed; in March, symptoms compatible with long-COVID (including psychometric scores) were asked and compared between HCW with positive NPS, seropositive HCW without positive NPS (presumable a-/pauci-symptomatic infections), and negative controls. Also, the effect of time since diagnosis and quantitative anti-S was evaluated. Poisson regression was used to identify risk factors for symptom occurrence. Results: Of 3334 HCW (median 41 years; 80% female), 556 (17%) had a positive NPS and 228 (7%) were only seropositive. HCW with positive NPS more frequently reported [≥]1 symptom compared to controls (73%vs.52%, p<0.001); seropositive HCW without positive NPS did not score higher than controls (58%vs.52%, p=0.13), although impaired taste/olfaction (16%vs.6%, p<0.001) and hair loss (17%vs.10%, p=0.004) were more common. Exhaustion/burnout was reported by 24% of negative controls. Many symptoms remained elevated in those diagnosed >6 months ago; anti-S titers correlated with high symptom scores. Acute viral symptoms in weekly questionnaires best predicted long-COVID symptoms. Physical activity at baseline was negatively associated with neurocognitive impairment and fatigue scores. Conclusions: Seropositive HCW without positive NPS are only mildly affected by long-COVID. Exhaustion/burnout is common, even in non-infected HCW. Physical activity might be protective against neurocognitive impairment/fatigue symptoms after COVID-19.

Results from Canton Grisons of Switzerland Suggest Repetitive Testing Reduces SARS-CoV-2 Incidence (February-March 2021) (preprint)

In February 2021, in response to emergence of more transmissible SARS-CoV-2 virus variants, the Canton Grisons launched a unique RNA mass testing program targeting the labour force in local businesses. Employees were offered weekly tests free of charge and on a voluntary basis. If tested positive, they were required to self-isolate for ten days and their contacts were subjected to daily testing at work. Thereby, the quarantine of contact persons could be waved. Here, we evaluate the effects of the testing program on the tested cohorts. We examined 121'364 test results from 27'514 participants during February-March 2021. By distinguishing different cohorts of employees, we observe a noticeable decrease in the test positivity rate and a statistically significant reduction in the associated incidence rate over the considered period. The reduction in the latter ranges between 18\%-50\%. The variability is partly explained by different exposures to exogenous infection sources (e.g., contacts with visiting tourists or cross-border commuters). Our analysis provides the first empirical evidence that applying repetitive mass testing to a real population over an extended period of time can prevent spread of COVID-19 pandemic. However, to overcome logistic, uptake, and adherence challenges it is important that the program is carefully designed and that disease incursion from the population outside of the program is considered and controlled.

Impact of baseline SARS-CoV-2 antibody status on syndromic surveillance and the risk of subsequent Covid-19 -- a prospective multicentre cohort study (preprint)

Objectives In a prospective healthcare worker (HCW) cohort, we assessed the risk of SARS-CoV-2 infection according to baseline serostatus. Methods Baseline serologies were performed among HCW from 23 Swiss healthcare institutions between June and September 2020, before the second COVID-19 wave. Participants answered weekly electronic questionnaires covering information about nasopharyngeal swabs (PCR/rapid antigen tests) and symptoms compatible with Coronavirus Disease 2019 (COVID-19). Screening of symptomatic staff by nasopharyngeal swabs was routinely performed in participating facilities. We compared numbers of positive nasopharyngeal tests and occurrence of COVID-19 symptoms between HCW with and without anti-nucleocapsid antibodies. Results A total of 4'818 HCW participated, whereof 144 (3%) were seropositive at baseline. We analysed 107'820 questionnaires with a median follow-up of 7.9 months. Median number of answered questionnaires was similar (24 vs. 23 per person, P=0.83) between those with and without positive baseline serology. Among 2'713 HCW with [≥]1 SARS-CoV-2 test during follow-up, 3/67 (4.5%) seropositive individuals reported a positive result (one of whom asymptomatic), compared to 547/2646 (20.7%) seronegative participants, 12 of whom asymptomatic (risk ratio [RR] 0.22; 95% confidence interval [CI] 0.07 to 0.66). Seropositive HCWs less frequently reported impaired olfaction/taste (6/144, 4.2% vs. 588/4674, 12.6%, RR 0.33, 95%-CI: 0.15-0.73), chills (19/144, 13.2% vs. 1040/4674, 22.3%, RR 0.59, 95%-CI: 0.39-0.90), and limb/muscle pain (28/144, 19.4% vs. 1335/4674, 28.6%, RR 0.68 95%-CI: 0.49-0.95). Impaired olfaction/taste and limb/muscle pain also discriminated best between positive and negative SARS-CoV-2 results. Conclusions Having SARS-CoV-2 anti-nucleocapsid antibodies provides almost 80% protection against SARS-CoV-2 re-infection for a period of at least eight months.

Use of respirator vs. surgical masks in healthcare personnel and its impact on SARS-CoV-2 acquisition – a prospective multicentre cohort study (preprint)

ABSTRACT Background There is insufficient evidence regarding the role of respirators in the prevention of SARS-CoV-2 infection. We analysed the impact of filtering facepiece class 2 (FFP2) vs . surgical masks on the risk of SARS-CoV-2 acquisition among Swiss healthcare workers (HCW). Methods Our prospective multicentre cohort enrolled patient-facing HCWs from June to August 2020. Participants were asked about COVID-19 risk exposures/behaviours, including preferred mask type when caring for COVID-19 patients outside of aerosol-generating procedures (AGP). For those performing AGPs, we asked whether they used FFP2 irrespective of the patient’s COVID-19 status (i.e. universal use). The impact of FFP2 on i) self-reported SARS-CoV-2-positive nasopharyngeal PCR/rapid antigen tests captured during weekly surveys, and ii) SARS-CoV-2 seroconversion between baseline and January/February 2021 was assessed. Results We enrolled 3’259 participants from nine healthcare institutions, whereof 716 (22%) preferentially used FFP2 respirators. Among these, 81/716 (11%) reported a SARS-CoV-2-positive swab, compared to 352/2543 (14%) surgical mask users (median follow-up 242 days); seroconversion was documented in 85/656 (13%) FFP2 and 426/2255 (19%) surgical mask users. Adjusted for baseline characteristics, COVID-19 exposure, and risk behaviour, FFP2 use was non-significantly associated with a decreased risk for SARS-CoV-2-positive swab (adjusted hazard ratio [aHR] 0·8, 95% CI 0·6-1·0, p=0·052) and seroconversion (adjusted odds ratio [aOR] 0·7, 95% CI 0·5-1·0, p=0·053); household exposure was the strongest risk factor (aHR for positive swab 10·1, p<0·001; aOR for seroconversion 5·0, p<0·001). In subgroup analysis, FFP2 use was clearly protective among those with frequent (>20 patients) COVID-19 exposure (aHR 0·7, p<0·001; aOR 0·6, p=0·035). Universal FFP2 use during AGPs showed no protective effect (aHR 1·1, p=0·7; aOR 0·9, p=0·53). Conclusion Respirators compared to surgical masks may convey additional protection from SARS-CoV-2 for HCW with frequent exposure to COVID-19 patients. Funding Swiss National Sciences Foundation, Federal Office of Public Health, Cantonal Health Department St.Gallen

Quantification of the spread of SARS-CoV-2 variant B.1.1.7 in Switzerland (preprint)

In December 2020, the United Kingdom (UK) reported a SARS-CoV-2 Variant of Concern (VoC) which is now coined B.1.1.7. Based on the UK data and later additional data from other countries, a transmission advantage of around 40-80% was estimated for this variant. In Switzerland, since spring 2020, we perform whole genome sequencing of SARS-CoV-2 samples obtained from a large diagnostic lab (Viollier AG) on a weekly basis for genomic surveillance. The lab processes SARS-CoV-2 samples from across Switzerland. Based on a total of 7631 sequences obtained from samples collected between 14.12.2020 and 11.02.2021 at Viollier AG, we determine the relative proportion of the B.1.1.7 variant on a daily basis. In addition, we use data from a second lab (Dr Risch) screening all their samples for the B.1.1.7 variant. These two datasets represent 11.5 % of all SARS-CoV-2 confirmed cases across Switzerland during the considered time period. They allow us to quantify the transmission advantage of the B.1.1.7 variant on a national and a regional scale. Taking all our data and estimates together, we propose a transmission advantage of 49-65% of B.1.1.7 compared to the other circulating variants. Further, we estimate the effective reproductive number through time for B.1.1.7 and the other variants, again pointing to a higher transmission rate of B.1.1.7. In particular, for the time period 01.01.2021-17.01.2021, we estimate an average reproductive number for B.1.1.7 of 1.28 [1.07-1.49] while the estimate for the other variants is 0.83 [0.63-1.03], based on the total number of confirmed cases and our Viollier sequencing data. Switzerland tightened measures on 18.01.2021. A comparison of the empirically confirmed case numbers up to 20.02.2021 to a very simple model using the estimates of the reproductive number from the first half of January provides indication that the rate of spread of all variants slowed down recently. In summary, the dynamics of increase in frequency of B.1.1.7 is as expected based on the observations in the UK. Our plots are available online and constantly updated with new data to closely monitor the changes in absolute numbers.

Quantifying Antibodies Directed against the SARS-CoV-2 Spike Protein S1 Subunit (preprint)

With the COVID-19 pandemic causing a global health crisis, accurate diagnosis is critical. Diagnosing acute disease relies on RT-PCR tests measuring the presence of SARS-CoV-2 in the sampled material but in patients with suspected COVID-19 with a negative RT-PCR result, measuring anti-viral antibodies can help clinicians identify infected individuals. Antibody testing can also determine if someone was previously infected and help to measure the prevalence of the virus in a community. A new study characterizes an assay measuring total antibodies – combined IgA, IgM, and IgG isotypes – against SARS-CoV-2. The assay, ECLIA, specifically measures antibodies against the S1 subunit of the viral spike, which carries the virus’s receptor binding domain. Researchers in Liechtenstein evaluated ECLIA in a population with 125 cases of confirmed SARS-CoV-2 infection and 1159 individuals without evidence of COVID-19. The results showed a test sensitivity of 97.6%, while the specificity was 99.8%. Antibody levels were highest in hospitalized patients and lower in symptomatic patients outside the hospital and those with asymptomatic infection. Following COVID-19, smokers developed lower antibody titers than non-smokers, whereas patients without fever had lower antibody titers than patients with fever. Following COVID-19, smokers developed lower antibody titers than non-smokers, whereas patients without fever had lower antibody titers than patients with fever suggesting that the assay may be able to test the association between clinical characteristics and antibody levels and help identify individuals with potential cross-reactivity to SARS-CoV-2.

IgA autoantibodies target pulmonary surfactant in patients with severe COVID-19 (preprint)

Complications affecting the lung are hallmarks of severe coronavirus disease 2019 (COVID-19). While there is evidence for autoimmunity in severe COVID-19, the exact mechanisms remain unknown. Here, we established a prospective observational cohort to study lung specific autoantibodies (auto-Abs). Incubation of plasma from severe COVID-19 patients with healthy human lung tissue revealed the presence of IgA antibodies binding to surfactant-producing pneumocytes. Enzyme-linked immunosorbent assays (ELISA) and protein pull-downs using porcine surfactant confirmed the presence of auto-Abs binding to surfactant proteins in severe COVID-19 patients. Mass spectrometry and ELISAs with recombinant proteins identified IgA auto-Abs that target human surfactant proteins B and C. In line with these findings, lungs of deceased COVID-19 patients showed reduced pulmonary surfactant. Our data suggest that IgA-driven autoimmunity against surfactant may result in disease progression of COVID-19.

Safety evaluation of a medical congress held during the COVID-19 pandemic – a prospective cohort (preprint)

Background Worldwide, scientific congresses are cancelled because of the COVID-19 pandemic. Yet, scientific exchange is more important than ever, especially for infectious diseases and infection prevention specialists. Within a prospective cohort of congress attendees, we evaluated the safety concept of the 2020 congress of the Swiss Societies of Infectious Diseases and Hospital Hygiene.Methods The congress was held between September 2nd and 4th 2020 in Geneva (Switzerland), where COVID-19 incidence in the week during the congress was 65 cases /100 000 population within 7 days. A rigorous safety concept was implemented including universal face masking, physical distancing during sessions, and maximal reduction of social events. We invited congress attendees to participate in this prospective cohort and used an anonymized online questionnaire to assess risk perception, risk exposures, symptoms and diagnosis of SARS-CoV-2 of attendees before, during and after the congress. Dried blood spots were taken from attendees on-site and four weeks later to detect specific antibodies against SARS-CoV-2 and to document seroconversions.Results A total of 365 people attended the congress, thereof 271 healthcare professionals. Of these, 196 (54%) either answered the questionnaire (N = 150) or provided baseline and follow-up blood samples (N = 168). None of the study participants reported a positive PCR result in the 2 weeks after the congress. Five of 168 (3%) participants were seropositive at follow-up, all of which had already been positive at baseline. The safety concept was deemed appropriate by 92% of the study participants and hygiene measures were performed correctly by the vast majority.Conclusion In this prospective cohort of congress attendees, no PCR positive cases or seroconversions could be documented after attending an on-site medical congress. These findings indicate that congresses with a rigorous safety concept may take place, even in areas with moderately-high COVID-19 activity.

Non-occupational and occupational factors associated with specific SARS-CoV-2 antibodies among Hospital Workers - a multicentre cross-sectional study (preprint)

Background Protecting healthcare workers (HCW) from Coronavirus Disease-19 (COVID-19) is critical to preserve the functioning of healthcare systems. We therefore assessed seroprevalence and identified risk factors for Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) seropositivity in this population. Methods Between June 22nd and August 15th 2020, employees from healthcare institutions in Northern/Eastern Switzerland were screened for SARS-CoV-2 antibodies. We recorded baseline characteristics, non-occupational and occupational risk factors. We used pairwise tests of associations and multivariable logistic regression to identify factors associated with seropositivity. Findings Among the 4664 included HCW from 23 healthcare facilities, 139 (3%) were seropositive. Non-occupational exposures independently associated with seropositivity were contact with a COVID-19 positive household (adjusted OR=54, 95%-CI: 31-97) and stay in a COVID 19 hotspot (aOR=2.2, 95%-CI: 1.1-3.9). Blood group 0 vs. non-0 (aOR=0.4, 95%-CI: 0.3-0.7), active smoking (aOR=0.5, 95%-CI: 0.3-0.9) and living with children <12 years (aOR=0.3, 95%-CI: 0.2-0.6) were associated with decreased risk. Occupational risk factors were close contact to COVID-19 patients (aOR=2.8, 95%-CI: 1.5-5.5), exposure to COVID-19 positive co-workers (aOR=2.0, 95%-CI: 1.2-3.1), poor knowledge of standard hygiene precautions (aOR=2.0, 95%-CI: 1.3-3.2), and frequent visits to the hospital canteen (aOR=1.9, 95%-CI: 1.2-3.1). Interpretation We identified several modifiable factors associated with SARS-CoV-2 seropositivity among our HCW. Living with COVID-19 positive households showed by far the strongest association. The lower risk among those living with children, even after correction for multiple confounders, is remarkable and merits further study. Funding Swiss National Sciences Foundation, Federal Office of Public Health, Health Department Canton of St. Gallen

Characteristics of three different chemiluminescence assays for testing for SARS-CoV-2 antibodies (preprint)

Several tests based on chemiluminescence immunoassay techniques have become available to test for SARS-CoV-2 antibodies. There is currently insufficient data on serology assay performance beyond 35 days after symptoms onset. We aimed to evaluate SARS-CoV-2 antibody tests on three widely used platforms. A chemiluminescent microparticle immunoassay (CMIA; Abbott Diagnostics, USA), a luminescence immunoassay (LIA; Diasorin, Italy), and an electrochemiluminescence immunoassay (ECLIA; Roche Diagnostics, Switzerland) were investigated. In a multi-group study, sensitivity was assessed in a group of participants with confirmed SARS-CoV-2 (n=145), whereas specificity was determined in two groups of participants without evidence of COVID-19 (i.e. healthy blood donors, n=191, and healthcare workers, n=1002). Receiver operating characteristic (ROC) curves, multilevel likelihood ratios (LR), and positive (PPV) and negative (NPV) predictive values were characterized. Finally, analytical specificity was characterized in samples with evidence of Epstein-Barr virus (EBV) (n=9), cytomegalovirus (CMV) (n=7) and endemic common cold coronavirus infections (n=12) taken prior to the current SARS-CoV-2 pandemic. The diagnostic accuracy was comparable in all three assays (AUC 0.98). Using the manufacturers cut-offs, the sensitivities were 90%, 95% confidence interval,[84,94] (LIA), 93% [88,96] (CMIA), and 96% [91,98] (ECLIA). The specificities were 99.5% [98.9,99.8](CMIA) 99.7% [99.3,99,9] (LIA) and 99.9% [99.5,99.98] (ECLIA). The LR at half of the manufacturers cut-offs were 60 (CMIA), 82 (LIA), and 575 (ECLIA) for positive and 0.043 (CMIA) and 0.035 (LIA, ECLIA) for negative results. ECLIA had higher PPV at low pretest probabilities than CMIA and LIA. No interference with EBV or CMV infection was observed, whereas endemic coronavirus in some cases provided signals in LIA and/or CMIA. Although the diagnostic accuracy of the three investigated assays is comparable, their performance in low-prevalence settings is different. Introducing gray zones at half of the manufacturers cut-offs is suggested, especially for orthogonal testing approaches that use a second assay for confirmation.

Temporal course of SARS-CoV-2 antibody positivity in patients with COVID-19 following the first clinical presentation (preprint)

Knowledge of the sensitivities of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibody tests beyond 35 days after the clinical onset of COVID-19 is insufficient. We aimed to describe positivity rate of SARS-CoV-2 assays employing three different measurement principles over a prolonged period. Two hundred sixty-eight samples from 180 symptomatic patients with COVID-19 and a reverse transcription polymerase chain reaction (RT-PCR) test followed by serological investigation of SARS-CoV-2 antibodies were included.. We conducted three chemiluminescence (including electrochemiluminscence, ECLIA), four enzyme linked immunosorbent assay (ELISA), and one lateral flow immunoassay (LFIA) test formats. Positivity rates, as well as positive (PPV) and negative predictive values (NPV) were calculated for each week after the first clinical presentation for COVID-19. Furthermore, combinations of tests were assessed within an orthogonal testing approach employing two independent assays and predictive values were calculated. Heat maps were constructed to graphically illustrate operational test characteristics. During a follow-up period of more than 9 weeks, chemiluminescence assays and one ELISA IgG test showed stable positivity rates after the third week. With the exception of ECLIA, the PPVs of the other chemiluminescence assays were [≥]95% for COVID-19 only after the second week. ELISA and LFIA had somewhat lower PPVs. IgM exhibited insufficient predictive characteristics. An orthogonal testing approach provided PPVs [≥]95% for patients with a moderate pretest probability (e.g., symptomatic patients), even for tests with a low single test performance. After the second week, NPVs of all but IgM assays were [≥]95% for patients with low to moderate pretest probability. The confirmation of negative results using an orthogonal algorithm with another assay provided lower NPVs than the single assays. When interpreting results from SARS-CoV-2 tests, the pretest probability, time of blood draw and assay characteristics must be carefully considered. An orthogonal testing approach increases the accuracy of positive, but not negative, predictions.

Severe COVID-19 is associated with elevated serum IgA and antiphospholipid IgA-antibodies (preprint)

BackgroundWhile the pathogenesis of coronavirus disease 2019 (COVID-19) is becoming increasingly clear, there is little data on IgA response, the first line of bronchial immune defense. ObjectiveTo determine, whether COVID-19 is associated with a vigorous total IgA response and whether IgA autoantibodies are associated with complications of severe illness. Since thrombotic events are frequent in severe COVID-19 and resemble hypercoagulation of antiphospholipid syndrome (APS), our approach focused on antiphospholipid antibodies (aPL). Materials and methodsIn this retrospective cohort study we compared clinical data and aPL from 64 patients with COVID-19 from three independent centers (two in Switzerland, one in Liechtenstein). Samples were collected from April 9, 2020 to May 1, 2020. Total IgA and aPL were measured with FDA-approved commercially available clinical diagnostic kits. ResultsClinical records of the 64 patients with COVID-19 were reviewed and divided into a cohort with mild illness (mCOVID, n=26 [41%]), a discovery cohort with severe illness (sdCOVD, n=14 [22%]) and a confirmation cohort with severe illness (scCOVID, n=24 [38%]). Severe illness was significantly associated with increased total IgA (sdCOVID, P=0.01; scCOVID, P<0.001). Total IgG levels were similar in both cohorts. Among aPL, both cohorts with severe illness significantly correlated with elevated anti-Cardiolipin IgA (sdCOVID and scCOVID, P<0.001), anti-Cardiolipin IgM (sdCOVID, P=0.003; scCOVID, P<0.001), and anti-Beta2 Glycoprotein-1 IgA (sdCOVID and scCOVID, P<0.001). Systemic lupus erythematosus was excluded from all patients as a potential confounder of APS. ConclusionsHigher total IgA and IgA-aPL were consistently associated with severe illness. These novel data strongly suggest that a vigorous antiviral IgA-response triggered in the bronchial mucosa induces systemic autoimmunity.