Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, Minnesota, in the Prevaccination Era.

Objective: To estimate rates and identify factors associated with asymptomatic COVID-19 in the population of Olmsted County during the prevaccination era. Patients and Methods: We screened first responders (n=191) and Olmsted County employees (n=564) for antibodies to SARS-CoV-2 from November 1, 2020 to February 28, 2021 to estimate seroprevalence and asymptomatic infection. Second, we retrieved all polymerase chain reaction (PCR)-confirmed COVID-19 diagnoses in Olmsted County from March 2020 through January 2021, abstracted symptom information, estimated rates of asymptomatic infection and examined related factors. Results: Twenty (10.5%; 95% CI, 6.9%-15.6%) first responders and 38 (6.7%; 95% CI, 5.0%-9.1%) county employees had positive antibodies; an additional 5 (2.6%) and 10 (1.8%) had prior positive PCR tests per self-report or medical record, but no antibodies detected. Of persons with symptom information, 4 of 20 (20%; 95% CI, 3.0%-37.0%) first responders and 10 of 39 (26%; 95% CI, 12.6%-40.0%) county employees were asymptomatic. Of 6020 positive PCR tests in Olmsted County with symptom information between March 1, 2020, and January 31, 2021, 6% (n=385; 95% CI, 5.8%-7.1%) were asymptomatic. Factors associated with asymptomatic disease included age (0-18 years [odds ratio {OR}, 2.3; 95% CI, 1.7-3.1] and >65 years [OR, 1.40; 95% CI, 1.0-2.0] compared with ages 19-44 years), body mass index (overweight [OR, 0.58; 95% CI, 0.44-0.77] or obese [OR, 0.48; 95% CI, 0.57-0.62] compared with normal or underweight) and tests after November 20, 2020 ([OR, 1.35; 95% CI, 1.13-1.71] compared with prior dates). Conclusion: Asymptomatic rates in Olmsted County before COVID-19 vaccine rollout ranged from 6% to 25%, and younger age, normal weight, and later tests dates were associated with asymptomatic infection.

Performance Characteristics of High-Throughput Serologic Assays for Severe Acute Respiratory Syndrome Coronavirus 2 with Food and Drug Administration Emergency Use Authorization: A Review.

This review provides a broad summary of the performance characteristics of high-throughput severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serologic assays with Food and Drug Administration Emergency Use Authorization, which are commonly found in central clinical laboratories. In addition, this review discusses the current roles of serologic testing for SARS-CoV-2 and provides a perspective for the future.

Serological fingerprints link antiviral activity of therapeutic antibodies to affinity and concentration.

The effectiveness of therapeutic monoclonal antibodies (mAbs) against variants of the SARS-CoV-2 virus is highly variable. As target recognition of mAbs relies on tight binding affinity, we assessed the affinities of five therapeutic mAbs to the receptor binding domain (RBD) of wild type (A), Delta (B.1.617.2), and Omicron BA.1 SARS-CoV-2 (B.1.1.529.1) spike using microfluidic diffusional sizing (MDS). Four therapeutic mAbs showed strongly reduced affinity to Omicron BA.1 RBD, whereas one (sotrovimab) was less impacted. These affinity reductions correlate with reduced antiviral activities suggesting that affinity could serve as a rapid indicator for activity before time-consuming virus neutralization assays are performed. We also compared the same mAbs to serological fingerprints (affinity and concentration) obtained by MDS of antibodies in sera of 65 convalescent individuals. The affinities of the therapeutic mAbs to wild type and Delta RBD were similar to the serum antibody response, indicating high antiviral activities. For Omicron BA.1 RBD, only sotrovimab retained affinities within the range of the serum antibody response, in agreement with high antiviral activity. These results suggest that serological fingerprints provide a route to evaluating affinity and antiviral activity of mAb drugs and could guide the development of new therapeutics.

Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, MN in the Pre-Vaccination Era

Objective To estimate rates and identify factors associated with asymptomatic COVID-19 in the population of Olmsted County during the pre-vaccination era. Patients and Methods We screened first responders (N=191) and Olmsted County employees (N=564) for antibodies to SARS-CoV-2 from November 2020 to February 2021 to estimate seroprevalence and asymptomatic infection. Second, we retrieved all PCR confirmed COVID-19 diagnoses in Olmsted County from March 2020 through January 2021, ed symptom information, estimated rates of asymptomatic infection and examined related factors. Results Twenty (10.5%;95%CI: 6.9%-15.6%) first responders and thirty-eight (6.7%;95% CI: 5.0%-9.1%) county employees had positive antibodies;an additional 5 (2.6%) and 10 (1.8%) had prior positive PCR tests per self-report or medical record, but no antibodies detected. Of persons with symptom information, 4/20, (20%, 95% CI: 3.0%-37.0%) of first responders and 10/39 (26%, 95% CI: 12.6%-40.0%) county employees, were asymptomatic. Of 6,020 positive PCR tests in Olmsted County with symptom information between March 1, 2020, and January 31, 2021, 6% (n=385;95% CI: 5.8%-7.1%) were asymptomatic. Factors associated with asymptomatic disease included age [0-18 years (OR=2.3, 95% CI: 1.7-3.1) and 65+ years (OR=1.40, 95% CI: 1.0-2.0) compared to ages 19-44 years], body-mass-index [overweight OR=0.58, 95% CI: 0.44-0.77) or obese (OR=0.48, 95% CI: 0.57-0.62) compared to normal or underweight] and tests after November 20, 2020 [(OR=1.35;95% CI: 1.13-1.71) compared to prior dates]. Conclusion Asymptomatic rates in Olmsted County prior to vaccine rollout ranged from 6-25%, and younger age, normal weight, and later tests dates were associated with asymptomatic infection.

Predictors of chronic COVID-19 symptoms in a community-based cohort of adults.

BACKGROUND: COVID-19 can cause some individuals to experience chronic symptoms. Rates and predictors of chronic COVID-19 symptoms are not fully elucidated. OBJECTIVE: To examine occurrence and patterns of post-acute sequelae of SARS-CoV2 infection (PASC) symptomatology and their relationship with demographics, acute COVID-19 symptoms and anti-SARS-CoV-2 IgG antibody responses. METHODS: A multi-stage observational study was performed of adults (≥18 years) from 5 US states. Participants completed two rounds of electronic surveys (May-July 2020; April-May 2021) and underwent testing to anti-SARS-CoV-2 nucleocapsid protein IgG antibody testing. Latent Class Analysis was used to identify clusters of chronic COVID-19 symptoms. RESULTS: Overall, 390 adults (median [25%ile, 75%ile] age: 42 [31, 54] years) with positive SARS-CoV-2 antibodies completed the follow-up survey; 92 (24.7%) had ≥1 chronic COVID-19 symptom, with 11-month median duration of persistent symptoms (range: 1-12 months). The most common chronic COVID-19 symptoms were fatigue (11.3%), change in smell (9.5%) or taste (5.6%), muscle or joint aches (5.4%) and weakness (4.6%). There were significantly higher proportions of ≥1 persistent COVID-19 symptom (31.5% vs. 18.6%; Chi-square, P = 0.004), and particularly fatigue (15.8% vs. 7.3%, P = 0.008) and headaches (5.4% vs. 1.0%, P = 0.011) in females compared to males. Chronic COVID-19 symptoms were also increased in individuals with ≥6 acute COVID-19 symptoms, Latent class analysis revealed 4 classes of symptoms. Latent class-1 (change of smell and taste) was associated with lower anti-SARS-CoV-2 antibody levels; class-2 and 3 (multiple chronic symptoms) were associated with higher anti-SARS-CoV-2 antibody levels and more severe acute COVID-19 infection. LIMITATIONS: Ambulatory cohort with less severe acute disease. CONCLUSION: Individuals with SARS-CoV-2 infection commonly experience chronic symptoms, most commonly fatigue, changes in smell or taste and muscle/joint aches. Female sex, severity of acute COVID-19 infection, and higher anti-SARS-CoV-2 IgG levels were associated with the highest risk of having chronic COVID-19 symptoms.

Predictors of seroconversion after coronavirus disease 2019 vaccination.

BACKGROUND: Vaccine nonresponse during the coronavirus disease 2019 (COVID-19) pandemic has considerable individual and societal risks. OBJECTIVE: To investigate the clinical characteristics of patients with lack of seroconversion after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: Demographic and clinical data were collected from 805 patients who had validated antibody assays against the SARS-CoV-2 spike protein at least 14 days after completion of their COVID-19 vaccination. Clinical characteristics from patients with a negative (< 0.4 U/mL) antibody response were assessed and summarized. RESULTS: A total of 622 (77.3%) patients attained seroconversion as defined by a titer of greater than or equal to 0.4 U/mL, whereas 183 out of 805 (22.7%) patients exhibited no seroconversion after vaccination against SARS-CoV-2. Univariately, older age (P = .02) and male sex were associated with a lower likelihood of seroconversion (P = .003). Therapy with immunosuppressive drugs was noted in 93 (50.8%) of seronegative patients with most (n = 83/93, 89.2%) receiving ongoing immunosuppressive therapy at the time of vaccination. Among the 134 (73.2%) seronegative patients with immunodeficiency, 110 (82.1%) had primary immunodeficiency. Cancer (n = 128, 69.9%), B cell depletion therapy (n = 90/115, 78.3%), and immunosuppressant steroid use (n = 71/93 on immunosuppressants, 76.3%) were the other common characteristics among the vaccine nonresponders. More importantly, our study did not evaluate the actual efficacy of COVID-19 vaccination. CONCLUSION: Vaccine responses vary by age and sex, with men showing lower rates of seroconversion as compared with women. Primary immunodeficiency along with active malignancy and ongoing immunosuppression with steroids or B cell depletion therapy appeared to be the most common characteristics for those with a lack of vaccine seroconversion after COVID-19 vaccination.

Detection of neutralizing antibodies against multiple SARS-CoV-2 strains in dried blood spots using cell-free PCR.

An easily implementable serological assay to accurately detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies is urgently needed to better track herd immunity, vaccine efficacy and vaccination rates. Herein, we report the Split-Oligonucleotide Neighboring Inhibition Assay (SONIA) which uses real-time qPCR to measure the ability of neutralizing antibodies to block binding between DNA-barcoded viral spike protein subunit 1 and the human angiotensin-converting enzyme 2 receptor protein. The SONIA neutralizing antibody assay using finger-prick dried blood spots displays 91-97% sensitivity and 100% specificity in comparison to the live-virus neutralization assays using matched serum specimens for multiple SARS-CoV-2 variants-of-concern. The multiplex version of this neutralizing antibody assay, using easily collectable finger-prick dried blood spots, can be a valuable tool to help reveal the impact of age, pre-existing health conditions, waning immunity, different vaccination schemes and the emergence of new variants-of-concern.

Limited Correlation between SARS-CoV-2 Serologic Assays for Identification of High-Titer COVID-19 Convalescent Plasma Using FDA Thresholds.

In August 2020, the Food and Drug Administration (FDA) Emergency Use Authorization (EUA) for COVID-19 convalescent plasma (CCP) specified 12 authorized serologic assays and associated assay-specific cutoff values for the selection of high-titer CCP for use in hospitalized patients. The criteria used for establishing these cutoff values remains unclear. Here, we compare the overall agreement and concordance of five serologic assays included in the August 2020 FDA EUA at both the manufacturer-recommended qualitative cutoff thresholds and at the FDA-indicated thresholds for high-titer CCP, using serum samples collected as part of the CCP Expanded Access Program (EAP). The qualitative positive percent agreement (PPA) across assays ranged from 92.3% to 98.8%. However, the high-titer categorization across assays varied significantly, with the PPA ranging from 26.5% to 82.7%. The Roche anti-NC ECLIA provided the lowest agreement compared to all other assays. Efforts to optimize high-titer cutoffs could reduce, although not eliminate, the discordance across assays. The consequences of using nonstandardized assays are apparent in our study, and the high-titer cutoffs chosen for each assay are not directly comparable to each other. The generalized findings in our study will be relevant to any future use of convalescent plasma for either COVID-19 or future pandemics of newly emerged pathogens. IMPORTANCE COVID-19 convalescent plasma (CCP) was one of the first therapeutic options available for the treatment of SARS-CoV-2 infections and continues to be used selectively for immunosuppressed patients. Given the emergence of novel SARS-CoV-2 variants which are resistant to treatment with available monoclonal antibody (MAb) therapy, CCP remains an important therapeutic consideration. The FDA has released several emergency use authorizations (EUA) that have specified which serological assays can be used for qualification of CCP, as well as assay-specific cutoffs that must be used to identify high-titer CCP. In this study, a cohort of donor CCP was assessed across multiple serological assays which received FDA EUA for qualification of CCP. This study indicates a high degree of discordance across the assays used to qualify CCP for clinical use, which may have precluded the optimal use of CCP, including during clinical trials. This study highlights the need for assay standardization early in the development of serological assays for emerging pathogens.

Serosurveillance after a COVID-19 vaccine campaign in a Swiss police cohort.

INTRODUCTION: To assess the risk for COVID-19 of police officers, we are studying the seroprevalence in a cohort. The baseline cross-sectional investigation was performed before a vaccination campaign in January/February 2021, and demonstrated a seroprevalence of 12.9%. Here, we demonstrate serosurveillance results after a vaccination campaign. METHODS: The cohort consists of 1022 study participants. The 3- and 6-month follow-up visits were performed in April/May and September 2021. Data on infection and vaccination rates were obtained via measuring antibodies to the nucleocapsid protein and spike protein and online questionnaires. RESULTS: The mean age of the population was 41 (SD 8.8) years, 72% were male and 76% had no comorbidity. Seroconversion was identified in 1.05% of the study population at the 3-month visit and in 0.73% at the 6-month visit, resulting in an infection rate of 1.8% over a time period of 6 months. In comparison, the infection rate in the general population over the same time period was higher (3.18%, p = .018). At the 6-month visit, 77.8% of participants reported being vaccinated once and 70.5% twice; 81% had an anti-S antibody titer of >250 U/ml and 87.1% of ≥2 U/ml. No significant association between infection and job role within the department, working region, or years of experience in the job was found. Anti-spike antibody titers of vaccinated study participants showed a calculated decreasing trend 150-200 days after the second vaccine dose. CONCLUSION: These data confirm the value of the vaccination campaign in an exposed group other than healthcare professionals.

A multicenter evaluation of computable phenotyping approaches for SARS-CoV-2 infection and COVID-19 hospitalizations.

Diagnosis codes are used to study SARS-CoV2 infections and COVID-19 hospitalizations in administrative and electronic health record (EHR) data. Using EHR data (April 2020-March 2021) at the Yale-New Haven Health System and the three hospital systems of the Mayo Clinic, computable phenotype definitions based on ICD-10 diagnosis of COVID-19 (U07.1) were evaluated against positive SARS-CoV-2 PCR or antigen tests. We included 69,423 patients at Yale and 75,748 at Mayo Clinic with either a diagnosis code or a positive SARS-CoV-2 test. The precision and recall of a COVID-19 diagnosis for a positive test were 68.8% and 83.3%, respectively, at Yale, with higher precision (95%) and lower recall (63.5%) at Mayo Clinic, varying between 59.2% in Rochester to 97.3% in Arizona. For hospitalizations with a principal COVID-19 diagnosis, 94.8% at Yale and 80.5% at Mayo Clinic had an associated positive laboratory test, with secondary diagnosis of COVID-19 identifying additional patients. These patients had a twofold higher inhospital mortality than based on principal diagnosis. Standardization of coding practices is needed before the use of diagnosis codes in clinical research and epidemiological surveillance of COVID-19.

Immunity to SARS-CoV-2: What Do We Know and Should We Be Testing for It?

Preexisting immunity to Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) was nonexistent in humans, which coupled with high transmission rates of certain SARS-CoV-2 variants and limited vaccine uptake or availability, has collectively resulted in an ongoing global pandemic. The identification and establishment of one or multiple correlates of protection (CoP) against infectious pathogens is challenging, but beneficial from both the patient care and public health perspectives. Multiple studies have shown that neutralizing antibodies, whether generated following SARS-CoV-2 infection, vaccination, or a combination of both (i.e., hybrid immunity), as well as adaptive cellular immune responses, serve as CoPs for COVID-19. However, the diverse number and type of serologic assays, alongside the lack of cross-assay standardization and emergence of new SARS-CoV-2 variants with immune evasive characteristics, have collectively posed challenges to determining a robust CoP 'threshold' and for the routine utilization of these assays to document 'immunity,' as is commonly done for other vaccine preventable diseases. Here, we discuss what CoPs are, review our current understanding of infection-induced, vaccine-elicited and hybrid immunity to COVID-19 and summarize the current and potential future utility of SARS-CoV-2 serologic testing.

Association of Varying Clinical Manifestations and Positive Anti-SARS-CoV-2 IgG Antibodies: A Cross-Sectional Observational Study.

BACKGROUND: The complex relationship between clinical manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and individual immune responses is not fully elucidated. OBJECTIVE: To examine phenotypes of symptomatology and their relationship with positive anti-SARS-CoV-2 IgG antibody responses. METHODS: An observational study was performed of adults (≥18 years) from 5 US states. Participants completed an electronic survey and underwent testing to anti-SARS-CoV-2 nucleocapsid protein IgG antibody between May and July 2020. Latent class analysis was used to identify characteristic symptom clusters. RESULTS: Overall, 9507 adults (mean age, 39.6 ± 15.0 years) completed the survey; 6665 (70.1%) underwent antibody testing for anti-SARS-CoV-2 IgG. Positive SARS-CoV-2 antibodies were associated with self-reported positive SARS-CoV-2 nasal swab result (bivariable logistic regression; odds ratio [95% CI], 5.98 [4.83-7.41]), household with 6 or more members (1.27 [1.14-1.41]) and sick contact (3.65 [3.19-4.17]), and older age (50-69 years: 1.55 [1.37-1.76]; ≥70 years: 1.52 [1.16-1.99]), but inversely associated with female sex (0.61 [0.55-0.68]). Latent class analysis revealed 8 latent classes of symptoms. Latent classes 1 (all symptoms) and 4 (fever, cough, muscle ache, anosmia, dysgeusia, and headache) were associated with the highest proportion (62.0% and 57.4%) of positive antibodies, whereas classes 6 (fever, cough, muscle ache, headache) and 8 (anosmia, dysgeusia) had intermediate proportions (48.2% and 40.5%), and classes 3 (headache, diarrhea, stomach pain) and 7 (no symptoms) had the lowest proportion (7.8% and 8.5%) of positive antibodies. CONCLUSIONS: SARS-CoV-2 infections manifest with substantial diversity of symptoms, which are associated with variable anti-SARS-CoV-2 IgG antibody responses. Prolonged fever, anosmia, and receiving supplemental oxygen therapy had strongest associations with positive SARS-CoV-2 IgG.

Antigen Specific Humoral and Cellular Immunity Following SARS-CoV-2 Vaccination in ANCA-Associated Vasculitis Patients Receiving B-Cell Depleting Therapy.

Humoral vaccine responses are known to be suboptimal in patients receiving B-cell targeted therapy, and little is known about vaccine induced T-cell immunity in these patients. In this study, we characterized humoral and cellular antigen-specific anti-SARS-CoV2 responses following COVID-19 vaccination in patients with ANCA-associated vasculitis (AAV) receiving anti-CD20 therapy, who were either B-cell depleted, or B-cell recovered at the time of vaccination and in normal control subjects. SARS-CoV-2 anti-spike (S) and anti-nucleocapsid (NC) antibodies were measured using electrochemiluminescence immunoassays, while SARS-CoV-2 specific T-cell responses to S glycoprotein subunits 1 (S1) and 2 (S2) and receptor binding domain peptide pools were measured using interferon-gamma enzyme-linked immunosorbent spot (ELISPOT) assays. In total, 26 recently vaccinated subjects were studied. Despite the lack of a measurable humoral immune response, B-cell depleted patients mounted a similar vaccine induced antigen-specific T-cell response compared to B-cell recovered patients and normal controls. Our data indicate that to assure a humoral response in patients receiving anti-CD20 therapy, SARS-CoV-2 vaccination should ideally be delayed until B-cell recovery (CD-20 positive B-cells > 10/µl). Nevertheless, SARS-CoV-2 vaccination elicits robust, potentially protective cellular immune responses in these subjects. Further research to characterize the durability and protective effect of vaccine-induced anti-SARS-CoV-2 specific T-cell immunity are needed.

A Multidimensional Cross-Sectional Analysis of Coronavirus Disease 2019 Seroprevalence Among a Police Officer Cohort: The PoliCOV-19 Study.

BACKGROUND: Protests and police fieldwork provide a high-exposure environment for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. In this cross-sectional analysis, we investigated the seroprevalence among a police cohort, and sociodemographic, work, and health-related factors associated with seropositivity. METHODS: Study participants were invited for serological testing of SARS-CoV-2 and to complete online questionnaires. Serum neutralization titers toward the wild-type SARS-CoV-2 spike protein (expressing D614G) and the Alpha and Beta variants were measured in seropositive study participants. RESULTS: A total of 978 police personnel representing 35% of the entire staff participated from February to March 2021. The seroprevalence was 12.9%. It varied by geographic region, ranged from 9% to 13.5% in 3 regions, including the city; and was 22% in Bernese Seeland/Jura with higher odds for seropositivity (odds ratio [OR], 2.38 [95% confidence interval {CI}, 1.28-4.44], P=.006). Job roles with mainly office activity were associated with a lower risk of seropositivity (OR, 0.33 [95% CI, .14-.77], P=.010). Self-reported compliance with mask wearing during working hours was 100%; 45% of seropositive vs 5% of seronegative participants (P<.001) reported having had contact with a proven coronavirus disease 2019 (COVID-19) case living in the same household prior to serological testing. The level of serum antibody titers correlated with neutralization capacity. Antibodies derived from natural SARS-CoV-2 infection effectively neutralized the SARS-CoV-2 spike protein, but were less effective against the Alpha and Beta variants. CONCLUSIONS: The seroprevalence of anti-SARS-CoV-2 antibodies of police officers was comparable to that reported in the general population, suggesting that the personal protective equipment of the police is effective, and that household contacts are the leading transmission venues. The level of serum antibody titers, in particular that of anti-spike antibodies, correlated well with neutralization capacity. Low antibody titers acquired from natural infection were not effective against variants. CLINICAL TRIALS REGISTRATION: NCT04643444.

SARS-CoV-2 Serologic Assays Dependent on Dual-Antigen Binding Demonstrate Diverging Kinetics Relative to Other Antibody Detection Methods.

Longitudinal studies assessing durability of the anti-severe acute respiratory syndrome coronavirus 2 (anti-SARS-CoV-2) humoral immune response have generated conflicting results. This has been proposed to be due to differences in patient populations, the lack of standardized methodologies, and the use of assays that measure distinct aspects of the humoral response. SARS-CoV-2 antibodies were serially measured in sera from a cohort of 44 well-characterized convalescent plasma donors over 120 days post-COVID-19 symptom onset, utilizing eight assays, which varied according to antigen source, the detected antibody isotype, and the activity measured (i.e., binding, blocking, or neutralizing). While the majority of assays demonstrated a gradual decline in antibody titers over the course of 120 days, the two electrochemiluminescence immunoassay Roche assays (Roche Diagnostics Elecsys anti-SARS-CoV-2 [qualitative, nucleocapsid based] and Roche Diagnostics Elecsys anti-SARS-CoV-2 S [semiquantitative, spike based]), which utilize dual-antigen binding for antibody detection, demonstrated stable and/or increasing antibody titers over the study period. This study is among the first to assess longitudinal, rather than cross-sectional, SARS-CoV-2 antibody profiles among convalescent COVID-19 patients, primarily using commercially available serologic assays with Food and Drug Administration emergency use authorization. We show that SARS-CoV-2 antibody detection is dependent on the serologic method used, which has implications for future assay utilization and clinical value.

Validation of a multiplex flow immunoassay for detection of IgG antibodies against SARS-CoV-2 in dried blood spots.

BACKGROUND: Dried blood spots (DBS) are an established specimen type for clinical testing given their low cost, ease of collection and storage, and convenient shipping capabilities through the postal system. These attributes are complementary to the expansion of SARS-CoV-2 serologic testing, which may be used to inform community seroprevalence rates. METHODS: The Luminex xMAP SARS-CoV-2 Multi-Antigen assay utilizes magnetic beads labeled with three viral antigens (nucleocapsid [NC], receptor binding domain [RBD], spike S1 subunit) to detect anti-viral IgG-class antibodies, and has Food and Drug Administration (FDA) Emergency Use Authorization (EUA) for use in serum and plasma. This assay was modified for use with DBS and validated against paired sera tested by one of two reference assays: the Roche Diagnostics Elecsys anti-SARS-CoV-2 ECLIA or the Euroimmun anti-SARS-CoV-2 IgG ELISA. RESULTS: 159 paired DBS and serum specimens analyzed using the modified Luminex xMAP assay on DBS and the reference methods on serum showed an overall concordance of 96.9% (154/159). Use of multivariate pattern recognition software (CLIR) for post-analytical interpretation of the Luminex xMAP DBS assay results, instead of manufacturer provided interpretive thresholds, increased overall qualitative result concordance to 99.4% (158/159) between the modified Luminex xMAP DBS and reference results. CONCLUSIONS: Use of DBS for detection of antibodies against SARS-CoV-2 provides comparable results to those obtained using serum. DBS concordance was improved with multivariate pattern recognition software (CLIR). We demonstrate that DBS are a reliable specimen type for SARS-CoV-2 antibody detection using the modified Luminex xMAP assay.

AACC Practical Recommendations for Implementing and Interpreting SARS-CoV-2 Emergency Use Authorization and Laboratory-Developed Test Serologic Testing in Clinical Laboratories.

BACKGROUND: The clinical laboratory continues to play a critical role in managing the coronavirus pandemic. Numerous US Food and Drug Administration emergency use authorization (EUA) and laboratory-developed test (LDT) serologic assays have become available. The performance characteristics of these assays and their clinical utility continue to be defined in real time during this pandemic. The AACC convened a panel of experts from clinical chemistry, microbiology, and immunology laboratories; the in vitro diagnostics industry; and regulatory agencies to provide practical recommendations for implementation and interpretation of these serologic tests in clinical laboratories. CONTENT: The currently available EUA serologic tests and platforms, information on assay design, antibody classes including neutralizing antibodies, and the humoral immune responses to SARS-CoV-2 are discussed. Verification and validation of EUA and LDT assays are described, along with a quality management approach. Four indications for serologic testing are outlined. Recommendations for result interpretation, reporting comments, and the role of orthogonal testing are also presented. SUMMARY: This document aims to provide a comprehensive reference for laboratory professionals and healthcare workers to appropriately implement SARS-CoV-2 serologic assays in the clinical laboratory and to interpret test results during this pandemic. Given the more frequent occurrence of outbreaks associated with either vector-borne or respiratory pathogens, this document will be a useful resource in planning for similar scenarios in the future.

Mortality in individuals treated with COVID-19 convalescent plasma varies with the geographic provenance of donors.

Successful therapeutics and vaccines for coronavirus disease 2019 (COVID-19) have harnessed the immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Evidence that SARS-CoV-2 exists as locally evolving variants suggests that immunological differences may impact the effectiveness of antibody-based treatments such as convalescent plasma and vaccines. Considering that near-sourced convalescent plasma likely reflects the antigenic composition of local viral strains, we hypothesize that convalescent plasma has a higher efficacy, as defined by death within 30 days of transfusion, when the convalescent plasma donor and treated patient were in close geographic proximity. Results of a series of modeling techniques applied to approximately 28,000 patients from the Expanded Access to Convalescent Plasma program (ClinicalTrials.gov number: NCT04338360) support this hypothesis. This work has implications for the interpretation of clinical studies, the ability to develop effective COVID-19 treatments, and, potentially, for the effectiveness of COVID-19 vaccines as additional locally-evolving variants continue to emerge.