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Hajilooi M, Keramat F, Moazenian A, Rastegari-Pouyani M, Solgi G. The quantity and quality of anti-SARS-CoV-2 antibodies show contrariwise association with COVID-19 severity: lessons learned from IgG avidity. Med Microbiol Immunol 2023; 212:203-220. [PMID: 37103583 PMCID: PMC10133916 DOI: 10.1007/s00430-023-00763-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 04/07/2023] [Indexed: 04/28/2023]
Abstract
Gaining more appreciation on the protective/damaging aspects of anti-SARS-CoV-2 immunity associated with disease severity is of great importance. This study aimed to evaluate the avidity of serum IgG antibodies against SARS-CoV-2 spike (S) and nucleocapsid (N) in hospitalized symptomatic COVID-19 patients and asymptomatic RT-PCR-confirmed SARS-CoV-2 carriers as well as to compare antibody avidities with respect to vaccination status, vaccination dose and reinfection status. Serum levels of anti-S and anti-N IgG were determined using specific ELISA kits. Antibody avidity was determined by urea dissociation assay and expressed as avidity index (AI) value. Despite higher IgG levels in the symptomatic group, AI values of both anti-S and anti-N IgG were significantly lower in this group compared to asymptomatic individuals. In both groups, anti-S AI values were elevated in one-dose and two-dose vaccinees versus unvaccinated subjects, although significant differences were only detected in the symptomatic group. However, anti-N avidity showed no significant difference between the vaccinated and unvaccinated subgroups. Almost all vaccinated patients of different subgroups (based on vaccine type) had higher anti-S IgG avidity, while the statistical significance was detected only between those receiving Sinopharm compared to the unvaccinated subgroup. Also, statistically significant differences in antibody AIs were only found between primarily infected individuals of the two groups. Our findings indicate a key role for anti-SARS-CoV-2 IgG avidity in protection from symptomatic COVID-19 and calls for the incorporation of antibody avidity measurement into the current diagnostic tests to predict effective immunity toward SARS-CoV-2 infection or even for prognostic purposes.
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Affiliation(s)
- Mehrdad Hajilooi
- Department of Immunology, School of Medicine, Hamadan University of Medical Sciences, Shahid Fahmideh Blvd, Opposite to Lona Park, P.O. Box 6517838736, Hamadan, Iran
| | - Fariba Keramat
- Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
- Department of Infectious Diseases, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Akram Moazenian
- Department of Immunology, School of Medicine, Hamadan University of Medical Sciences, Shahid Fahmideh Blvd, Opposite to Lona Park, P.O. Box 6517838736, Hamadan, Iran
| | - Mohsen Rastegari-Pouyani
- Department of Immunology, School of Medicine, Hamadan University of Medical Sciences, Shahid Fahmideh Blvd, Opposite to Lona Park, P.O. Box 6517838736, Hamadan, Iran.
- Cancer Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
| | - Ghasem Solgi
- Department of Immunology, School of Medicine, Hamadan University of Medical Sciences, Shahid Fahmideh Blvd, Opposite to Lona Park, P.O. Box 6517838736, Hamadan, Iran.
- Cancer Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
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Han T, Wang X, Cao H, Song J, Deng X, Gong G, Huang L, Lu Y, Wang Z. Novel Method for Adulterated Identification of Saneen Goat Milk Based on Free Oligosaccharides α3'-Galactosyllactose and N-Acetylhexaminyllactose as Marker Molecules. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:5667-5673. [PMID: 36995191 DOI: 10.1021/acs.jafc.2c08649] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Methods for the detection of adulterated milk are essential for assessing the quality of goat milk products. We hypothesized that goat milk oligosaccharides could provide a basis for this purpose and compared the levels of α3'-galactosyllactose (α3'-GL) and N-acetylhexaminyllactose (NHL) between goat milk and bovine milk oligosaccharides using reverse-phase high-performance liquid chromatography. The α3'-GL was detected to be three times more abundant in goat milk than in bovine milk, whereas NHL showed the opposite trend. Linear relationships were established between the relative proportions of α3'-GL and NHL levels for different ratios of bovine and goat milk, with a minimum detection limit of 2% bovine milk. The new method was validated by analyses of adulterants in eight commercially available goat dairy products. Overall, the degree of adulteration in goat milk products can be determined based on the relative proportions of α3'-GL and NHL.
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Affiliation(s)
- Tianjiao Han
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Xinyi Wang
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Haige Cao
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Jiansen Song
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Xiaoli Deng
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Guiping Gong
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Linjuan Huang
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Yu Lu
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
| | - Zhongfu Wang
- Shaanxi Natural Carbohydrate Resource Engineering Research Center, College of Food Science and Technology, Northwest University, Xi'an 710069, China
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Dai S, Li J, Li J, Li L, Shi L, Cao L, Zhong X, Liu W, Wang Y, Ma L. Analysis of 4 cases of children with false-positive results of novel coronavirus-specific antibody. BMC Pediatr 2022; 22:372. [PMID: 35765042 PMCID: PMC9237983 DOI: 10.1186/s12887-022-03425-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 06/17/2022] [Indexed: 12/15/2022] Open
Abstract
Abstract
Background
This study attempts to explore the influencing factors and solutions of the colloidal gold method for novel coronavirus (2019-nCoV)-specific IgM/IgG antibody detection, summarize the clinical experience and perfect the examination process, improving the application value of antibody detection in COVID-19 diagnosis.
Methods
A total of 13,329 peripheral whole blood/plasma/serum samples were obtained for COVID-19 screening from children who visited the Children's Hospital of the Capital Institute of Pediatrics outpatient clinic from April 22, 2020, to November 30, 2020. The colloidal gold method was adopted for 2019-nCoV-specific IgM/IgG antibody detection. The virus nucleic acid test results, clinical records, and serum protein fingerprint results of antibody-positive patients were collected.
Results
All samples were examined using the colloidal gold method with two 2019-nCoV-specific IgM/IgG antibody detection kits. Four patients were tested single antibody-positive using both kits. The details were as follows: two cases of IgM ( +) and IgG (-) using plasma and serum separately, two cases of IgM (-) and IgG ( +) using serum and whole blood. The protein fingerprinting results and nucleic acid tests of 2019-nCoV antibodies were negative in the 4 cases. Considering the epidemiological history, clinical manifestations, and test results, these 4 children were ruled out for 2019-nCoV infection.
Conclusions
When the colloidal gold method was used to detect 2019-nCoV-specific IgM/IgG antibodies, it was important to ascertain the test results as precisely as possible. Specimen type and patient history may interfere with the diagnosis.
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Salim H, Pero-Gascon R, Giménez E, Benavente F. On-line Coupling of Aptamer Affinity Solid-Phase Extraction and Immobilized Enzyme Microreactor Capillary Electrophoresis-Mass Spectrometry for the Sensitive Targeted Bottom-Up Analysis of Protein Biomarkers. Anal Chem 2022; 94:6948-6956. [PMID: 35500203 PMCID: PMC9118193 DOI: 10.1021/acs.analchem.1c03800] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In this paper, we present a fully integrated valve-free method for the sensitive targeted bottom-up analysis of proteins through on-line aptamer affinity solid-phase extraction and immobilized enzyme microreactor capillary electrophoresis-mass spectrometry (AA-SPE-IMER-CE-MS). The method was developed analyzing α-synuclein (α-syn), which is a protein biomarker related to different neurodegenerative disorders, including Parkinson's disease. Under optimized conditions, on-line purification and preconcentration of α-syn, enzymatic digestion, electrophoretic separation, and identification of the tryptic peptides by mass spectrometry was achieved in less than 35 min. The limit of detection was 0.02 μg mL-1 of digested protein (66.7% of coverage, i.e., 8 out of 12 expected tryptic peptides were detected). This value was 125 and 10 times lower than for independent on-line digestion by IMER-CE-MS (2.5 μg mL-1) and on-line preconcentration by AA-SPE-CE-MS (0.2 μg mL-1). The repeatability of AA-SPE-IMER-CE-MS was adequate (at 0.5 μg mL-1,% RSD ranged from 3.7 to 16.9% for peak areas and 3.5 to 7.7% for migration times of the tryptic peptides), and the modified capillary could be reused up to 10 analyses with optimum performance, similarly to IMER-CE-MS. The method was subsequently applied to the analysis of endogenous α-syn from red blood cell lysates. Ten α-syn tryptic peptides were detected (83.3% of coverage), enabling the characterization and localization of post-translational modifications of blood α-syn (i.e., N-terminal acetylation).
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Affiliation(s)
- Hiba Salim
- Department of Chemical Engineering and Analytical Chemistry, Institute for Research on Nutrition and Food Safety (INSA·UB), University of Barcelona, 08028 Barcelona, Spain
| | - Roger Pero-Gascon
- Department of Chemical Engineering and Analytical Chemistry, Institute for Research on Nutrition and Food Safety (INSA·UB), University of Barcelona, 08028 Barcelona, Spain
| | - Estela Giménez
- Department of Chemical Engineering and Analytical Chemistry, Institute for Research on Nutrition and Food Safety (INSA·UB), University of Barcelona, 08028 Barcelona, Spain
| | - Fernando Benavente
- Department of Chemical Engineering and Analytical Chemistry, Institute for Research on Nutrition and Food Safety (INSA·UB), University of Barcelona, 08028 Barcelona, Spain
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Conzentino MS, Gonçalves ACA, Paula NM, Rego FGM, Zanette DL, Aoki MN, Nardin JM, Huergo LF. A magnetic bead immunoassay to detect high affinity human IgG reactive to SARS-CoV-2 Spike S1 RBD produced in Escherichia coli. Braz J Microbiol 2022; 53:1263-1269. [PMID: 35426068 PMCID: PMC9009495 DOI: 10.1007/s42770-022-00753-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 04/08/2022] [Indexed: 12/03/2022] Open
Abstract
Immunological assays to detect SARS-CoV-2 Spike Receptor Binding Domain (RBD) antigen seroconversion in humans are important tools to monitor the levels of protecting antibodies in the population in response to infection and/or immunization. Here we describe a simple, low cost, and high throughput Ni2+ magnetic bead immunoassay to detect human IgG reactive to Spike S1 RBD Receptor Binding Domain produced in Escherichia coli. A 6xHis-tagged Spike S1 RBD was expressed in E. coli and purified by affinity chromatography. The protein was mobilized on the surface of Ni2+ magnetic beads and used to investigate the presence of reactive IgG in the serum obtained from pre-pandemic and COVID-19 confirmed cases. The method was validated with a cohort of 290 samples and an area under the receiver operating characteristic curve of 0.94 was obtained. The method was operated with > 82% sensitivity at 98% specificity and was also able to track human IgG raised in response to vaccination with Comirnaty at > 85% sensitivity. The IgG signal obtained with the described method was well-correlated with the signal obtained when pre fusion Spike produced in HEK cell lines was used as antigen. This novel low-cost and high throughput immunoassay may act as an important tool to investigate protecting IgG antibodies against SARS-CoV-2 in the human population.
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Affiliation(s)
- Marcelo S Conzentino
- Setor Litoral, UFPR Matinhos, Rua Jaguariaíva, Tv. Caiobá, 512, Matinhos, 83260-000, PR, Brazil
| | - Ana C A Gonçalves
- Setor Litoral, UFPR Matinhos, Rua Jaguariaíva, Tv. Caiobá, 512, Matinhos, 83260-000, PR, Brazil
| | - Nigella M Paula
- Setor Litoral, UFPR Matinhos, Rua Jaguariaíva, Tv. Caiobá, 512, Matinhos, 83260-000, PR, Brazil
| | - Fabiane G M Rego
- Post-Graduation Program in Pharmaceutical Sciences, UFPR, Curitiba, PR, Brazil
| | | | - Mateus N Aoki
- Instituto Carlos Chagas - FioCruz, Curitiba, PR, Brazil
| | | | - Luciano Fernandes Huergo
- Setor Litoral, UFPR Matinhos, Rua Jaguariaíva, Tv. Caiobá, 512, Matinhos, 83260-000, PR, Brazil.
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6
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Evolution of Anti-RBD IgG Avidity Following SARS-CoV-2 Infection. Viruses 2022; 14:v14030532. [PMID: 35336940 PMCID: PMC8949389 DOI: 10.3390/v14030532] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 02/28/2022] [Accepted: 03/02/2022] [Indexed: 02/06/2023] Open
Abstract
SARS-CoV-2 infection rapidly elicits anti-Spike antibodies whose quantity in plasma gradually declines upon resolution of symptoms. This decline is part of the evolution of an immune response leading to B cell differentiation into short-lived antibody-secreting cells or resting memory B cells. At the same time, the ongoing class switch and antibody maturation processes occurring in germinal centers lead to the selection of B cell clones secreting antibodies with higher affinity for their cognate antigen, thereby improving their functional activity. To determine whether the decline in SARS-CoV-2 antibodies is paralleled with an increase in avidity of the anti-viral antibodies produced, we developed a simple assay to measure the avidity of anti-receptor binding domain (RBD) IgG elicited by SARS-CoV-2 infection. We longitudinally followed a cohort of 29 convalescent donors with blood samples collected between 6- and 32-weeks post-symptoms onset. We observed that, while the level of antibodies declines over time, the anti-RBD avidity progressively increases and correlates with the B cell class switch. Additionally, we observed that anti-RBD avidity increased similarly after SARS-CoV-2 mRNA vaccination and after SARS-CoV-2 infection. Our results suggest that anti-RBD IgG avidity determination could be a surrogate assay for antibody affinity maturation and, thus, suitable for studying humoral responses elicited by natural infection and/or vaccination.
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7
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Tauzin A, Gong SY, Beaudoin-Bussières G, Vézina D, Gasser R, Nault L, Marchitto L, Benlarbi M, Chatterjee D, Nayrac M, Laumaea A, Prévost J, Boutin M, Sannier G, Nicolas A, Bourassa C, Gendron-Lepage G, Medjahed H, Goyette G, Bo Y, Perreault J, Gokool L, Morrisseau C, Arlotto P, Bazin R, Dubé M, De Serres G, Brousseau N, Richard J, Rovito R, Côté M, Tremblay C, Marchetti GC, Duerr R, Martel-Laferrière V, Kaufmann DE, Finzi A. Strong humoral immune responses against SARS-CoV-2 Spike after BNT162b2 mRNA vaccination with a 16-week interval between doses. Cell Host Microbe 2022; 30:97-109.e5. [PMID: 34953513 PMCID: PMC8639412 DOI: 10.1016/j.chom.2021.12.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/08/2021] [Accepted: 11/29/2021] [Indexed: 12/21/2022]
Abstract
The standard regimen of the BNT162b2 mRNA vaccine for SARS-CoV-2 includes two doses administered three weeks apart. However, some public health authorities spaced these doses, raising questions about efficacy. We analyzed longitudinal humoral responses against the D614G strain and variants of concern for SARS-CoV-2 in a cohort of SARS-CoV-2-naive and previously infected individuals who received the BNT162b2 mRNA vaccine with sixteen weeks between doses. While administering a second dose to previously infected individuals did not significantly improve humoral responses, these responses significantly increased in naive individuals after a 16-week spaced second dose, achieving similar levels as in previously infected individuals. Comparing these responses to those elicited in individuals receiving a short (4-week) dose interval showed that a 16-week interval induced more robust responses among naive vaccinees. These findings suggest that a longer interval between vaccine doses does not compromise efficacy and may allow greater flexibility in vaccine administration.
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Affiliation(s)
- Alexandra Tauzin
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Shang Yu Gong
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Department of Microbiology and Immunology, McGill University, Montreal, QC H3A 2B4, Canada
| | - Guillaume Beaudoin-Bussières
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Dani Vézina
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada
| | - Romain Gasser
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Lauriane Nault
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Lorie Marchitto
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Mehdi Benlarbi
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada
| | | | - Manon Nayrac
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Annemarie Laumaea
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Jérémie Prévost
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Marianne Boutin
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Gérémy Sannier
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Alexandre Nicolas
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | | | | | | | | | - Yuxia Bo
- Department of Biochemistry, Microbiology and Immunology, and Center for Infection, Immunity, and Inflammation, University of Ottawa, Ottawa ON K1H 8M5, Canada
| | - Josée Perreault
- Héma-Québec, Affaires Médicales et Innovation, Quebec QC G1V 5C3, Canada
| | - Laurie Gokool
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada
| | | | | | - Renée Bazin
- Héma-Québec, Affaires Médicales et Innovation, Quebec QC G1V 5C3, Canada
| | - Mathieu Dubé
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada
| | - Gaston De Serres
- Institut National de Santé Publique du Québec, Quebec QC H2P 1E2, Canada
| | - Nicholas Brousseau
- Institut National de Santé Publique du Québec, Quebec QC H2P 1E2, Canada
| | - Jonathan Richard
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Roberta Rovito
- Clinic of Infectious Diseases, Department of Health Sciences, ASST Santi Paolo e Carlo, University of Milan, Milan, Italy
| | - Marceline Côté
- Department of Biochemistry, Microbiology and Immunology, and Center for Infection, Immunity, and Inflammation, University of Ottawa, Ottawa ON K1H 8M5, Canada
| | - Cécile Tremblay
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada
| | - Giulia C Marchetti
- Clinic of Infectious Diseases, Department of Health Sciences, ASST Santi Paolo e Carlo, University of Milan, Milan, Italy
| | - Ralf Duerr
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
| | - Valérie Martel-Laferrière
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada.
| | - Daniel E Kaufmann
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Médecine, Université de Montréal, Montreal, QC H3T 1J4, Canada.
| | - Andrés Finzi
- Centre de Recherche du CHUM, Montreal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada; Department of Microbiology and Immunology, McGill University, Montreal, QC H3A 2B4, Canada.
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Xiao X, Zhou Q, Zhu J, Sun L, Zhang H, Sun Y, Zhao J, Cui L. False-positive colloidal gold-based immunochromatographic strip assay reactions for antibodies to SARS-CoV-2 in patients with autoimmune diseases. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:534. [PMID: 33987232 DOI: 10.21037/atm-20-6509] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background The outbreak of the novel 2019 coronavirus disease (COVID-19) was declared a global pandemic by the World Health Organization (WHO) on March 11, 2020. The diagnosis of COVID-19 is frequently based on a positive serological test. We noted the occurrence of false-positive results for COVID-19 in the colloidal gold-based immunochromatographic strip (ICS) assay in sera from patients with autoimmune diseases (ADs). This study aimed to evaluate the possible reasons for the false-positive results in two ICS assays (Wondfo ICS and Innovita ICS) and to investigate the effect of urea dissociation in reducing false-positive results. Methods The sera of 135 patients with ADs, 13 confirmed COVID-19 patients, 95 disease controls, and 120 healthy controls were tested for immunoglobin M (IgM) and IgG against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using Wondfo and Innovita ICS kits. The distributions of auto-antibodies in antibody-positive and antibody-negative groups were also compared, and bivariable logistic regression was used to assess auto-antibodies associated with false-positive results. A urea dissociation test of ICS was performed for the SARS-CoV-2 antibody-positive samples. Results Specificity of Wondfo ICS for the 95 disease controls was 94.74% compared to 98.95% and 96.84% for Innovita SARS-CoV-2 IgM and IgG, respectively. Specificity of Wondfo ICS for the 120 healthy controls was 97.5% compared to 100% and 99.17% for Innovita SARS-CoV-2 IgM and IgG, respectively. Specificity of Wondfo ICS for AD patients was 73.33% compared to 97.78% and 96.30% for Innovita SARS-CoV-2 IgM and IgG, respectively. Sensitivity was 74.07% for Wondfo compared to 70.37% for Innovita IgM and 66.67% for Innovita IgG. Using the Wondfo ICS, the percentage of elevated rheumatoid factor (RF) level (>20 IU/mL) was higher in the SARS-CoV-2 antibody-positive group compared with the antibody-negative group [27/36 (75.0%) vs. 34/99 (34.34%), P=0.001]. The elevated RF was associated with antibody positivity, with an odds ratio of 4.671 [95% confidence interval (CI), 1.88-11.69]. The specificity of the Wondfo ICS assay for the AD patients was increased from 73.33% to 94.07% after the urea dissociation assay. Conclusions An elevated serum RF level could lead to false-positive results when detecting SARS-CoV-2 antibodies using the Wondfo ICS kit, and the urea dissociation assay would be helpful in reducing the incidence of false-positive results.
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Affiliation(s)
- Xiumei Xiao
- The Department of Laboratory Medicine, Peking University Third Hospital, Beijing, China
| | - Qingtao Zhou
- The Department of Respiratory and Critical Care Medicine, Peking University Third Hospital, Beijing, China
| | - Jinghao Zhu
- The Department of Laboratory Medicine, Peking University Third Hospital, Beijing, China
| | - Lin Sun
- The Department of Rheumatology and Immunology, Peking University Third Hospital, Beijing, China
| | - Hua Zhang
- Research Center of Clinical Epidemiology, Peking University Third Hospital, Beijing, China
| | - Yongchang Sun
- The Department of Respiratory and Critical Care Medicine, Peking University Third Hospital, Beijing, China
| | - Jinxia Zhao
- The Department of Rheumatology and Immunology, Peking University Third Hospital, Beijing, China
| | - Liyan Cui
- The Department of Laboratory Medicine, Peking University Third Hospital, Beijing, China
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9
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Ye Q, Zhang T, Lu D. Potential false-positive reasons for SARS-CoV-2 antibody testing and its solution. J Med Virol 2021; 93:4242-4246. [PMID: 33710634 PMCID: PMC8250967 DOI: 10.1002/jmv.26937] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 03/04/2021] [Accepted: 03/09/2021] [Indexed: 12/15/2022]
Abstract
Coronavirus disease 2019 (COVID-19) has brought a huge impact on global health and the economy. Early diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is essential for epidemic prevention and control. The detection of SARS-CoV-2 antibodies is an important criterion for diagnosing COVID-19. However, SARS-CoV-2 antibody testing also has certain false positives causing confusion in clinical diagnosis. This article summarizes the causes of false-positive detection of SARS-CoV-2 antibodies in clinical practice. The results indicate that the most common endogenous interferences include rheumatoid factor, heterophile antibodies, human anti-animal antibodies, lysozyme, complement, and cross-antigens. The exogenous interference is mainly incomplete coagulation of the specimen, contamination of the specimen, and insufficient optimization of the diagnostic kit's reaction system.
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Affiliation(s)
- Qing Ye
- Department of Clinical Laboratory, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, National Children's Regional Medical Center, Hangzhou, China
| | - Ting Zhang
- Laboratory Medicine Department, College of Medical Technology, Zhejiang Chinese Medical University, Hangzhou, China
| | - Dezhao Lu
- Laboratory Medicine Department, College of Medical Technology, Zhejiang Chinese Medical University, Hangzhou, China
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10
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Bossa F, Carparelli S, Latiano A, Palmieri O, Tavano F, Panza A, Pastore M, Marseglia A, D'Altilia M, Latiano T, Corritore G, Martino G, Nardella M, Guerra M, Terracciano F, Sacco M, Perri F, Andriulli A. Impact of the COVID-19 outbreak and the serum prevalence of SARS-CoV-2 antibodies in patients with inflammatory bowel disease treated with biologic drugs. Dig Liver Dis 2021; 53:277-282. [PMID: 33423942 PMCID: PMC7834247 DOI: 10.1016/j.dld.2020.12.120] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/24/2020] [Accepted: 12/31/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Patients receiving biologic therapies are at risk for viral infections. This study investigated the impact of the SARS-CoV-2 infection and the serum prevalence of SARS-CoV-2 antibodies in patients with inflammatory bowel disease (IBD) treated with biologic drugs. METHODS Information on demography, co-morbidities, clinical data regarding IBD, symptoms suggestive of the SARS-CoV-2 infection, close contacts with SARS-CoV-2 positive patients, hospitalization, and therapies administered for COVID-19 was collected for all patients who were being treated with biologic drugs. All patients underwent SARS-CoV-2 antibody testing. RESULTS Two hundred and fifty-nine patients (27 children) with a mean age of 42.2 ± 16.7 years (range 9 - 88) and a mean duration of disease of 13.4 ± 10 years (range 0.2 - 49) were enrolled. One hundred four patients (40.2%) had ulcerative colitis, and 155 (59.8%) had Crohn's disease. About the therapy: 62 patients were receiving infliximab, 89 adalimumab, 20 golimumab, 57 vedolizumab, 27 ustekinumab, 1 thalidomide, and 3 an experimental compound. The mean Charlson Comorbidity Index was 2. Thirty-two patients (12.3%) reported respiratory symptoms, and 2 of them were hospitalized (0.77%). Two patients resulted positive for IgG against SARS-CoV-2 (0.77%). CONCLUSIONS In patients with IBD, treatment with biologic drug does not represent a risk factor for the SARS-CoV-2 infection.
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Affiliation(s)
- Fabrizio Bossa
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy.
| | - Sonia Carparelli
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Anna Latiano
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Orazio Palmieri
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Francesca Tavano
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Anna Panza
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Maria Pastore
- Fondazione Casa Sollievo della Sofferenza, Division of Pediatrics, San Giovanni Rotondo, Italy
| | - Antonio Marseglia
- Fondazione Casa Sollievo della Sofferenza, Division of Pediatrics, San Giovanni Rotondo, Italy
| | - Mario D'Altilia
- Fondazione Casa Sollievo della Sofferenza, Division of Pediatrics, San Giovanni Rotondo, Italy
| | - Tiziana Latiano
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Giuseppe Corritore
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Giuseppina Martino
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Marianna Nardella
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Maria Guerra
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Fulvia Terracciano
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Michele Sacco
- Fondazione Casa Sollievo della Sofferenza, Division of Pediatrics, San Giovanni Rotondo, Italy
| | - Francesco Perri
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
| | - Angelo Andriulli
- Fondazione Casa Sollievo della Sofferenza, Division of Gastroenterology, San Giovanni Rotondo, Italy
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11
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Lu X, Zhang M, Liu W, Sheng N, Du Q, Zhang M, Guo X, Wang G, Wang Q. A method to alleviate false-positive results of the Elecsys HIV combi PT assay. Sci Rep 2021; 11:1033. [PMID: 33441741 PMCID: PMC7807026 DOI: 10.1038/s41598-020-80047-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 12/16/2020] [Indexed: 11/09/2022] Open
Abstract
To explore the effects of urea dissociation on reducing false-positive results of the Elecsys HIV combi PT assay. A retrospective analysis was used to evaluate the false-positive rate of the Elecsys HIV combi PT assay. Six false-positive sera, six positive sera and six sera from patients with early HIV infection were collected. Dissociation was performed using 1 mol/L, 2 mol/L, 4 mol/L, 6 mol/L, or 8 mol/L urea, and HIV screening assay were then detected to select the appropriate concentration of urea dissociation. Next, 55 false-positive sera and 15 sera from early HIV infection were used to verify the best concentration of urea to achieve dissociation. Retrospective analysis showed that the COI of the Elecsys HIV combi PT assay in false-positive sera ranged from 1.0 to 200.0, and approximately 97.01%(227/234) of false-positive sera were in the range of 1.0-15.0. The avidity index (AI) in positive and false-positive sera decreased as the urea dissociation concentration increased. When the dissociation concentration was 6 mol/L, the AI of false-positive serum was between 0.0234 and 0.2567, and the AI of early HIV infection sera was between 0.4325 and 0.5017. The difference in AI between false-positive and positive samples was significant. When negativity was defined as an AI of less than 0.3970, the sensitivity and specificity were 100.0% and 100.0%, respectively. Urea-mediated dissociation could significantly reduce the false-positive rate of the Elecsys HIV combi PT assay with a low COI. Our findings provided a reference for distinguishing positive and false-positive of the Elecsys HIV combi PT assay.
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Affiliation(s)
- Xiaolan Lu
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,College of Laboratory Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,Faculty of Laboratory Medicine, Center for Translational Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Minghong Zhang
- Nanchong Center for Disease Control and Prevention, Nanchong, Sichuan, People's Republic of China
| | - Wen Liu
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,College of Laboratory Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,Faculty of Laboratory Medicine, Center for Translational Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Nan Sheng
- Nanchong Center for Disease Control and Prevention, Nanchong, Sichuan, People's Republic of China
| | - Qin Du
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,College of Laboratory Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,Faculty of Laboratory Medicine, Center for Translational Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Maoxin Zhang
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Xiaolan Guo
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,College of Laboratory Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.,Faculty of Laboratory Medicine, Center for Translational Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Guangrong Wang
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China. .,College of Laboratory Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China. .,Faculty of Laboratory Medicine, Center for Translational Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.
| | - Qiang Wang
- Department of Laboratory Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China. .,College of Laboratory Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China. .,Faculty of Laboratory Medicine, Center for Translational Medicine, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.
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12
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False-positive results of SARS-CoV-2 IgM/IgG antibody tests in sera stored before the 2020 pandemic in Italy. Int J Infect Dis 2020; 104:159-163. [PMID: 33383223 PMCID: PMC7834192 DOI: 10.1016/j.ijid.2020.12.067] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 12/22/2020] [Accepted: 12/23/2020] [Indexed: 01/26/2023] Open
Abstract
OBJECTIVES Aside from the outbreak of the coronavirus disease 2019 (COVID-19), serological tests are not well known for their diagnostic value. We assessed the performance of serological tests using stored sera from patients with a variety of pathologic conditions, collected before the 2020 pandemic in Italy. METHODS Rapid lateral flow tests and Enzyme-Linked Immunosorbent Assays (ELISA) that detect Immunoglobulin M (IgM) and Immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were carried out using 1150 stored human serum samples that had been collected in 2018 and 2019. The tests were also run using samples from 15 control patients who had positive or negative oral swab test results, as assessed using real-time reverse transcription-polymerase chain reaction (rRT-PCR). The urea dissociation test was employed to rule out false-positive reactivity in the two antibody detection methods. RESULTS The lateral flow tests revealed 21 positive samples from the stored sera: 12 for IgM, four for IgG, and five for IgM/IgG. Among the nine rRT-PCR- positive controls, six individuals presented IgG and three IgM/IgG positivity. Using the urea (6 mol/L) dissociation test, two of the twelve stored samples that had shown IgM positivity were confirmed to be positive. The ELISA test detected four IgM-positive and three IgG-positive specimens. After treatment with 4 mol/L urea, the IgM-positive samples became negative, whereas the IgG positivity persisted. All of the rRT-PCR-positive controls were found to retain IgM or IgG positivity following the urea treatment. CONCLUSIONS Our findings highlight the limited utility of serological testing for the SARS-CoV-2 virus based on the results of specimens collected before the outbreak of the infection.
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13
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Development of a Novel Sensor System Based on Magnetic Microspheres to Detect Cardiac Troponin T. INT J POLYM SCI 2020. [DOI: 10.1155/2020/8855550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Acute myocardial infarction (AMI) causes irreversible injury to cardiomyocytes in a short time and may result in various complications, severely threatening patient safety. Therefore, it is necessary to predict the possibility of AMI in the prophase. Prognostic detection of biomarkers that specifically reflect myocardial damage in a patient’s blood has become an essential mediating measure to prevent the serious occurrence of AMI. The present study is aimed at exploring a novel sensing system with high specificity and precision based on magnetic microspheres developed to detect cardiac troponin T (cTnT), which is the most specific diagnostic marker for AMI in cardiovascular diseases. Naive human cTnT protein in serum samples and antigens on functional magnetic microspheres will competitively bind with limited specific antibodies. After rapid removal of heterogeneous elements in the sera using a magnetic separator, fluorescein isothiocyanate-labeled immunoglobulin G is added to react with specific antibodies on the magnetic microspheres. Then, a flow cytometer is used to collect signals of different fluorescence intensities. The results show that the method is characterized by economy, high accuracy, and novelty. It can be used for the detection of cTnT in blood at 1.7–106.1 ng/mL, with a detection limit of 0.5 ng/mL. Thus, the proposed sensor improves the accuracy and efficiency of diagnosis before clinical deterioration of AMI.
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Guzman NA, Guzman DE. A Two-Dimensional Affinity Capture and Separation Mini-Platform for the Isolation, Enrichment, and Quantification of Biomarkers and Its Potential Use for Liquid Biopsy. Biomedicines 2020; 8:biomedicines8080255. [PMID: 32751506 PMCID: PMC7459796 DOI: 10.3390/biomedicines8080255] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 07/22/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023] Open
Abstract
Biomarker detection for disease diagnosis, prognosis, and therapeutic response is becoming increasingly reliable and accessible. Particularly, the identification of circulating cell-free chemical and biochemical substances, cellular and subcellular entities, and extracellular vesicles has demonstrated promising applications in understanding the physiologic and pathologic conditions of an individual. Traditionally, tissue biopsy has been the gold standard for the diagnosis of many diseases, especially cancer. More recently, liquid biopsy for biomarker detection has emerged as a non-invasive or minimally invasive and less costly method for diagnosis of both cancerous and non-cancerous diseases, while also offering information on the progression or improvement of disease. Unfortunately, the standardization of analytical methods to isolate and quantify circulating cells and extracellular vesicles, as well as their extracted biochemical constituents, is still cumbersome, time-consuming, and expensive. To address these limitations, we have developed a prototype of a portable, miniaturized instrument that uses immunoaffinity capillary electrophoresis (IACE) to isolate, concentrate, and analyze cell-free biomarkers and/or tissue or cell extracts present in biological fluids. Isolation and concentration of analytes is accomplished through binding to one or more biorecognition affinity ligands immobilized to a solid support, while separation and analysis are achieved by high-resolution capillary electrophoresis (CE) coupled to one or more detectors. When compared to other existing methods, the process of this affinity capture, enrichment, release, and separation of one or a panel of biomarkers can be carried out on-line with the advantages of being rapid, automated, and cost-effective. Additionally, it has the potential to demonstrate high analytical sensitivity, specificity, and selectivity. As the potential of liquid biopsy grows, so too does the demand for technical advances. In this review, we therefore discuss applications and limitations of liquid biopsy and hope to introduce the idea that our affinity capture-separation device could be used as a form of point-of-care (POC) diagnostic technology to isolate, concentrate, and analyze circulating cells, extracellular vesicles, and viruses.
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Affiliation(s)
- Norberto A. Guzman
- Princeton Biochemicals, Inc., Princeton, NJ 08816, USA
- Correspondence: ; Tel.: +1-908-510-5258
| | - Daniel E. Guzman
- Princeton Biochemicals, Inc., Princeton, NJ 08816, USA
- Department of Internal Medicine, University of California at San Francisco, San Francisco, CA 94143, USA; or
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15
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A Method To Prevent SARS-CoV-2 IgM False Positives in Gold Immunochromatography and Enzyme-Linked Immunosorbent Assays. J Clin Microbiol 2020; 58:JCM.00375-20. [PMID: 32277023 PMCID: PMC7269408 DOI: 10.1128/jcm.00375-20] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 04/06/2020] [Indexed: 12/29/2022] Open
Abstract
We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 Mycoplasma pneumoniae IgM-positive sera, 5 Legionella pneumophila IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients. We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 Mycoplasma pneumoniae IgM-positive sera, 5 Legionella pneumophila IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients. The interference factors causing false-positive reactivity with the two methods were analyzed, and the urea dissociation test was employed to dissociate the SARS-CoV-2 IgM-positive serum using the best dissociation concentration. The two methods detected positive SARS-CoV-2 IgM in 22 mid-to-high-level-RF-IgM-positive sera and 14 sera from COVID-19 patients; the other 50 sera were negative. At a urea dissociation concentration of 6 mol/liter, SARS-CoV-2 IgM results were positive in 1 mid-to-high-level-RF-IgM-positive serum and in 14 COVID-19 patient sera detected using GICA. At a urea dissociation concentration of 4 mol/liter and with affinity index (AI) levels lower than 0.371 set to negative, SARS-CoV-2 IgM results were positive in 3 mid-to-high-level-RF-IgM-positive sera and in 14 COVID-19 patient sera detected using ELISA. The presence of RF-IgM at mid-to-high levels could lead to false-positive reactivity of SARS-CoV-2 IgM detected using GICA and ELISA, and urea dissociation tests would be helpful in reducing SARS-CoV-2 IgM false-positive results.
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