scholarly journals Dual-Antigen System Allows Elimination of False Positive Results in COVID-19 Serological Testing

Diagnostics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 102
Author(s):  
Andrei Komarov ◽  
Anna Kaznadzey ◽  
Yue Li ◽  
Maria Kireeva ◽  
Ilya Mazo
Keyword(s):  
Immune Response ◽  
False Positive ◽  
Serological Test ◽  
Polyclonal Antibodies ◽  
Epidemiological Studies ◽  
Human Organism ◽  
Elisa Format ◽  
Test Specificity ◽  
Antigen System ◽  
Positive Results

Determining the presence of antibodies in serum is important for epidemiological studies, to be able to confirm whether a person has been infected, predicting risks of them getting sick and spreading the disease. During the ongoing pandemic of COVID-19, a positive serological test result can suggest if it is safe to return to work and re-engage in social activities. Despite a multitude of emerging tests, the quality of respective data often remains ambiguous, yielding a significant fraction of false positive results. The human organism produces polyclonal antibodies specific to multiple viral proteins, so testing simultaneously for multiple antibodies appeared a practical approach for increasing test specificity. We analyzed immune response and testing potential for a spectrum of antigens derived from the spike and nucleocapsid proteins of SARS-CoV-2, developed a dual-antigen testing system in the ELISA format and designed a robust algorithm for data processing. Combining nucleocapsid protein and receptor-binding domain for analysis allowed us to completely eliminate false positive results in the tested cohort (achieving specificity within a 95% confidence interval of 97.2–100%). We also tested samples collected from different households, and demonstrated differences in the immune response of COVID-19 patients and their family members; identifying, in particular, asymptomatic cases showing strong presence of studied antibodies, and cases showing none despite confirmed close contacts with the infected individuals.

scholarly journals Biosensor Analysis of β-Lactams in Milk Using the Carboxypeptidase Activity of a Bacterial Penicillin Binding Protein

2006 ◽  
Vol 89 (3) ◽  
pp. 832-837 ◽  
Author(s):  
Åse SternesjÖ ◽  
Eva Gustavsson
Keyword(s):  
False Positive ◽  
Polyclonal Antibodies ◽  
Active Form ◽  
False Negative ◽  
Screening Tests ◽  
Receptor Protein ◽  
Penicillin G ◽  
Penicillin Binding Protein ◽  
Spr Biosensor ◽  
Positive Results

Abstract The applicability of a -lactam receptor protein for detection of β-lactam antibiotics in milk using surface plasmon resonance (SPR) biosensor technology was investigated. The advantage of using a receptor protein instead of antibodies for detection of β-lactams is that a generic assay, specific for the active form of the β-lactam structure, is obtained. Two assays based on the enzymatic activity of the dd-carboxypeptidase from Actinomadura R39 were developed, using a Biacore SPR biosensor. The carboxypeptidase converts a tri-peptide into a di-peptide, a reaction which is inhibited in the presence of β-lactams. Polyclonal antibodies against the 2 peptides were developed and used to measure the amount of enzymatic product formed (di-peptide assay) or the amount of remaining enzymatic substrate (tri-peptide assay), respectively. The 2 assays showed similar performances with respect to detection limits (1.2 and 1.5 μg/kg, respectively) and precision (coefficient of variation <5%) for penicillin G in milk. Several other β-lactams were detected at or near their respective maximum residue limit. Furthermore, the 2 peptide assays were evaluated against 5 commercial kit tests in the screening of 195 producer milk samples. The biosensor assays showed 0% false-negative and 27% false-positive results, whereas the figures were 0% false-negative and 2753% false-positive results for other screening tests investigated.

Production of Polyclonal Antibodies against Pregnancy Associated Glycoprotein in Cattle

2020 ◽  
Keyword(s):  
Gene Family ◽  
False Positive ◽  
Half Life ◽  
Hormone Level ◽  
Polyclonal Antibodies ◽  
Large Gene Family ◽  
Precise Method ◽  
Large Gene ◽  
High Level ◽  
Positive Results

Pregnancy-associated glycoproteins (PAGs) are considered to be a large gene family in the trophoblasts of ruminants. PAGs determination precisely, PAG-1 in serum has been as the solid ground for pregnancy diagnosis in cow. Unluckily the PAG-1 and the antigenically related PAGs show a long half-life in serum less than 8 days and can be assessed 80 to 100 das postpartum, thereafter giving false results in cows bred within 60 days of calving. This study involves using novel polyclonal antibodies after immunizing rabbits and purification of the produced antibodies. The cattle are pregnant when the PAG hormone level is measured in a high level in a serum sample from the animal. It could give a precise method of detecting pregnancy at the early with few false positive results.

Place of serological test-systems for detection of antibodies to SARS-CoV2 in emergency cardiac surgery

2021 ◽  
pp. 18-21
Author(s):  
O. V. Petrova ◽  
D. K. Tverdokhlebova ◽  
D. M. Nikulina ◽  
D. G. Tarasov
Keyword(s):  
Cardiac Surgery ◽  
Human Serum ◽  
False Positive ◽  
Laboratory Testing ◽  
Serological Test ◽  
Confirmatory Test ◽  
Serum Antibodies ◽  
Laboratory Assessment ◽  
Test Systems ◽  
Positive Results

The article reveals the need for a comprehensive laboratory assessment of testing for antibodies to SARS-CoV-2. In progress it is focused on the possible product of laboratory testing studies of false-positive results caused by the presence of human serum antibodies in that cross reacting with SARS-CoV-2 proteins. It is concluded that in order to reduce the proportion of false positive results of the study require the use of confirmatory test.

scholarly journals Meat juice serology for Toxoplasma gondii infection in chickens

2016 ◽  
Vol 5 (1) ◽  
Author(s):  
Alice Vismarra ◽  
Carlo Mangia ◽  
Elena Barilli ◽  
Franco Brindani ◽  
Cristina Bacci ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Serological Test ◽  
Epidemiological Studies ◽  
Heart Tissue ◽  
Sample Collection ◽  
Free Range ◽  
Meat Juice ◽  
Specific Pcr ◽  
Test Specificity ◽  
Toxoplasma Gondii Infection

<em>Toxoplasma gondii</em> is an important food-borne zoonoses. Free-range chickens are at particularly high risk of infection and are also excellent indicators of soil contamination by oocysts. In the present study, hearts of 77 free-range chickens were collected at slaughter. <em>T. gondii</em> meat juice ELISA was performed with a commercial kit, following validation with positive controls, from experimentally infected chickens, and negative ones. Out of 77 samples, only 66 gave sufficient meat juice for serology. Of these, 24 (36.4%) were positive for <em>T. gondii</em> considering the 5*SD values (calculated on the OD of negative controls) while all the samples were negative considering S/P% values. Parasite-specific PCR was carried out on all samples obtained from heart tissue and none were positive for the presence of T. gondii DNA. Results would suggest that further study on the use of meat juice with a validated serological test to detect <em>T. gondii</em> in chickens could lead to widespread epidemiological studies in this important intermediate host. However, sample collection and test specificity require further evaluation.

scholarly journals Interferences on microbial inhibitor tests related to ivermectin treatment in lactating dairy goats

2016 ◽  
Vol 83 (3) ◽  
pp. 341-344 ◽  
Author(s):  
Tamara Romero ◽  
Vicente Javier Moya ◽  
Nemesio Fernández ◽  
Rafael Althaus ◽  
Wim Reybroeck ◽  
...  
Keyword(s):  
Immune Response ◽  
False Positive ◽  
Sarcoptes Scabiei ◽  
Parasitic Disease ◽  
Ivermectin Treatment ◽  
Positive Outcomes ◽  
Drug Residues ◽  
Dairy Goats ◽  
Milk Samples ◽  
Positive Results

This Research Communication reports interferences related to the administration of ivermectin in lactating dairy goats on the response of microbial tests for screening antibiotics in milk. Twenty-eight Murciano-Granadina goats, naturally infested with Sarcoptes scabiei var. caprae, were treated with a subcutaneous injection of ivermectin (200 µg/kg b.w.). To prevent re-infestation, a second dose was applied 7 d later. Individual milk samples were collected, daily, up to 15 d post-treatment. Milk samples were analysed by microbial inhibitor tests (BRT MRL, Delvotest SP-NT MCS and Eclipse 100) and ivermectin residues were quantified by HPLC. A large number of positive results were obtained for all microbial tests, especially on the first day after treatment (BRT MRL = 46·4%; Delvotest SP-NT MCS = 14·3%; and Eclipse 100 = 17·8%). However, the highest concentration of drug residues in milk (24·3 ng/ml) was detected on the tenth day after treatment, when positive outcomes were relatively lower (BRT MRL = 17·8%; Delvotest SP-NT MCS = 10·7%; and Eclipse 100 = 7·4%). Results herein suggest that factors related to the ivermectin treatment other than drug residues in milk, or alterations produced by the parasitic disease itself affecting the immune response of animals, could be the cause of false-positive results in microbial tests. It can be concluded that the application of ivermectin in dairy goats infested with sarcoptes mange during lactation produces persistent drug residues in milk, and could also cause false-positive results in microbial inhibitor tests for screening antibiotics.

scholarly journals COVID-19 vaccination may cause FDG uptake beyond axillary area

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Vincent Fleury ◽  
Bruno Maucherat ◽  
Daniela Rusu ◽  
Frédéric Dumont ◽  
Caroline Rousseau
Keyword(s):  
Immune Response ◽  
False Positive ◽  
Fdg Pet ◽  
Case Presentation ◽  
Pet Ct ◽  
Vaccination History ◽  
History Of ◽  
Well Differentiated ◽  
Fdg Pet Ct ◽  
Positive Results

Abstract Background The vaccination immune response may induce false-positive 18F-FDG PET/CT uptake. Case presentation An extended supraclavicular lymph nodal activation after coronavirus disease 2019 (COVID-19) vaccination revealed on 18F-FDG PET/CT mimics a Virchow nodule in a patient with medical history of well-differentiated appendicular adenocarcinoma. Conclusion This case highlights a nodal activation beyond axillary area and the importance of documenting vaccination history at the time of scanning to avoid false-positive results.

Critical Evaluation of Impedance Phlebography for the Diagnosis of Deep Vein Thrombosis

1974 ◽  
Vol 31 (02) ◽  
pp. 273-278
Author(s):  
Kenneth K Wu ◽  
John C Hoak ◽  
Robert W Barnes ◽  
Stuart L Frankel
Keyword(s):  
Deep Vein Thrombosis ◽  
False Positive ◽  
False Negative ◽  
Critical Evaluation ◽  
Original Method ◽  
Vein Thrombosis ◽  
Negative Results ◽  
False Negative Results ◽  
Deep Vein ◽  
Positive Results

SummaryIn order to evaluate its daily variability and reliability, impedance phlebography was performed daily or on alternate days on 61 patients with deep vein thrombosis, of whom 47 also had 125I-fibrinogen uptake tests and 22 had radiographic venography. The results showed that impedance phlebography was highly variable and poorly reliable. False positive results were noted in 8 limbs (18%) and false negative results in 3 limbs (7%). Despite its being simple, rapid and noninvasive, its clinical usefulness is doubtful when performed according to the original method.

Comparison of two rapid tests for the detection of legionellaceae in water: a microbiological-immunological method and a commercial gene-probe testkit

1995 ◽  
Vol 31 (5-6) ◽  
pp. 403-406 ◽  
Author(s):  
E. Frahm ◽  
U. Obst
Keyword(s):  
Monoclonal Antibodies ◽  
Conventional Method ◽  
Standard Method ◽  
False Positive ◽  
Gene Probe ◽  
Immunological Method ◽  
Probe Test ◽  
Rapid Tests ◽  
Positive Results

Two recently developed Legionella detection tests, a microbiological-immunological method based on monoclonal antibodies (carried out as a colony-blot assay) and a commercial gene-probe testkit (the EnvironAmp Legionella Kit), are compared with the standard method. The colony-blot assay is faster than the conventional method; the gene-probe test is much faster still and is the most sensitive, but in consequence is at greater risk of false-positive results.

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