Sandwich dot-immunogold filtration assay (DIGFA) for specific immunodiagnosis of active neuroangiostrongyliasis

Parasitology ◽  
2020 ◽  
pp. 1-6
Author(s):  
Praphathip Eamsobhana ◽  
Anchalee Tungtrongchitr ◽  
Hoi-Sen Yong ◽  
Anchana Prasartvit ◽  
Darawan Wanachiwanawin ◽  
...  
Keyword(s):  
False Negative ◽  
Clinical Samples ◽  
Serum Samples ◽  
Serological Tests ◽  
Past Infection ◽  
Negative Results ◽  
Resource Limited ◽  
False Negative Results ◽  
Circulating Antigens ◽  
Specific Antigens

Abstract Serological tests may yield false-negative results for specific antibodies detection before or at the early seroconversion phase. Tests that detect circulating antigens of Angiostrongylus cantonensis would therefore be of value in diagnosis to distinguish current or past infection. Here, a quick, easy to perform, portable and inexpensive diagnostic device for detection of 31-kDa A. cantonensis specific antigens had been developed. This sandwich dot-immunogold filtration assay (AcDIGFAAg), for detecting active angiostrongyliasis was produced using anti-A. cantonensis polyclonal antibody dotted on the nitrocellulose membrane as a capture agent and colloidal gold-labelled anti-31 kDa A. cantonensis antibody as a detection agent. A well-defined pink dot, indicating positivity, was seen readily by naked eye within 10–15 min. The AcDIGFAAg detected A. cantonensis-specific antigens in cerebrospinal fluid samples from 4 out of 10 serologically confirmed angiostrongyliasis cases and 2 out of 5 suspected cases with negative anti-A. cantonensis antibodies. Among the 19 patient sera with A. cantonensis infection, 2 showed positive reaction by AcDIGFAAg. No positive AcDIGFAAg reaction was observed in all the serum samples with other parasitic diseases, and the healthy controls. The present ‘AcDIGFAAg’ enables rapid qualitative detection of the specific 31-kDa antigens of A. cantonensis in clinical samples with potential for application even under resource-limited settings.

scholarly journals Detection of LytA Genes in Streptococcus pneumoniae Isolated from sputum pneumonia patients

Biomedika ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 23-30
Author(s):  
Mustika Sari Hutabarat ◽  
Firdaus Hamid ◽  
Irawaty Djaharuddin ◽  
Alfian Zainuddin ◽  
Rossana Agus ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
False Negative ◽  
Pneumococcal Infection ◽  
Diagnostic Methods ◽  
Molecular Diagnostic ◽  
Clinical Samples ◽  
Biochemical Tests ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain

Streptococcus pneumoniae (pneumococcus) is a Gram-positive facultative anaerobic bacterium that is a major cause of morbidity and mortality worldwide. But the lack of reporting of disease by this bacterium in Indonesia, one of the causes is because the diagnosis of pneumococcal infection is often clinically not typical and conventional methods which are still the standard gold method often give false-negative results. So the purpose of this study was to evaluate the performance of culture and molecular diagnostic methods using the Polymerase Chain Reaction (PCR) technique in detecting Streptococcus pneumoniae in sputum clinical samples using the Autolysin (LytA) gene which is a virulence factor of this bacterium. 57 isolates from 60 samples were confirmed as Streptococcus sp through microscopic identification, culture, and biochemical tests. Then the sensitivity test with an optochin test of 9 (9%) compared the results descriptively with the PCR technique using the Autolysin A (LytA) gene which was obtained more sensitive by 15 (25%).

scholarly journals False negative results in the Roche assay for HDL-cholesterol

2003 ◽  
Vol 40 (5) ◽  
pp. 572-575 ◽  
Author(s):  
Andries J Bakker ◽  
Appie Zijlstra ◽  
Marten P Leemhuis
Keyword(s):  
Cardiovascular Disease ◽  
Risk Evaluation ◽  
False Negative ◽  
Hdl Cholesterol ◽  
Daily Practice ◽  
Vascular Risk ◽  
Serum Samples ◽  
Negative Results ◽  
Risk Estimates ◽  
False Negative Results

Measurement of HDL-cholesterol is important in the risk evaluation of cardiovascular disease. Recently, we encountered a 61-year-old man with a negative result for HDL-cholesterol using the Roche assay. Further analysis revealed that this patient had a monoclonal Ig type IgM κ, with an electrophoresis-based concentration of 55.8 g/L, which apparently caused the negative result for HDL-cholesterol. Analysis of serum samples from other patients with monoclonal or polyclonal hypergammaglobulinaemia revealed that false negative results in the Roche assay for HDL-cholesterol may occur incidentally. Since negative results are detected easily in the laboratory, such patients do not pose a problem in daily practice. However, it is reasonable to suppose that false low results could also be caused by monoclonal as well as polyclonal Igs. Since such false low results remain undetected, vascular risk estimates consequently are altered and unnecessary treatment might be started.

scholarly journals The Use of a Mimic to Detect Polymerase Chain Reaction– Inhibitory Factors in Feces Examined for the Presence of Lawsonia Intracellularis

2003 ◽  
Vol 15 (3) ◽  
pp. 268-273 ◽  
Author(s):  
Magdalena Jacobson ◽  
Stina Englund ◽  
András Ballagi-Pordány
Keyword(s):  
Polymerase Chain Reaction ◽  
False Negative ◽  
Clinical Samples ◽  
Lawsonia Intracellularis ◽  
Chain Reaction ◽  
Fecal Samples ◽  
Wild Boars ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain

Lawsonia intracellularis is an intracellular organism that causes proliferative enteritis in pigs. This bacterium is difficult to culture, and antemortem demonstration of the microbe is therefore often performed on fecal samples by polymerase chain reaction (PCR). Polymerase chain reaction is sensitive and specific, but inhibitory factors in feces might cause false-negative results. This article describes the construction and use of an internal standard, a mimic. The mimic is amplified by the same primers as those used for L. intracellularis DNA and thus could indicate false-negative results in clinical samples. The amplicon was clearly visible when as few as 10 mimic molecules were added per amplification reaction and when no inhibitors were present. When fecal samples were spiked with the mimic, the detection limit was 102 molecules per PCR. Sixty clinical samples, 20 from wild boars, 20 from growing pigs with diarrhea, and 20 from pigs without diarrhea, were prepared by a boiling procedure and subjected to PCR together with 103 mimic molecules. Nine samples were positive, of which 7 originated from pigs with diarrhea and 2 from pigs without diarrhea. In 14 samples from wild boars, in 8 samples from pigs without diarrhea, and in 3 samples from pigs with diarrhea, neither the mimic nor the target DNA was visible. This indicated the presence of inhibitors in these samples. It is concluded that the mimic can be used as an internal control in the diagnosis of L. intracellularis to indicate inhibition of PCR.

scholarly journals SARS-CoV-2 RNA detection using pooling of self-collected samples: Simple protocol may foster asymptomatic surveillance

2020 ◽  
Author(s):  
Giselle Ibette Lopez-Lopes ◽  
Rita de Cassia Compagnoli Carmona ◽  
Valéria Oliveira Silva ◽  
Cintia Mayumi Ahagon ◽  
Lincoln Spinazola do Prado ◽  
...  
Keyword(s):  
False Negative ◽  
Clinical Samples ◽  
Rna Detection ◽  
Negative Results ◽  
False Negative Results ◽  
Throat Wash ◽  
Asymptomatic Volunteers ◽  
Simple Protocol ◽  
Antigen Tests ◽  
Public Health Institute

1AbstractBackgroundSurveillance of COVID infection and isolation of infected individuals is one of the available tools to control the spread of SAR-CoV-2. Asymptomatic and pre symptomatic are responsible for substantial transmission. RNA or antigen tests are necessary to identify non-symptomatic individuals. We tested the feasibility of using samples pooling offering different collection alternatives (swab/throat wash/saliva) to volunteers of a public health institute.MethodsWe evaluated pool samples from frozen material from previously tested samples and a prospective collection from asymptomatic volunteers. Some collections were paired for comparison. Pools and some individual samples were extracted with QIAamp Viral RNA Mini Kit (Qiagen, USA) and/or Lucigen Quick Extract DNA extraction solution (BioSearch, USA) and submitted to rtPCR (Allplex, Seegene, Korea).ResultsA total of 240 samples from 130 new collections and 37 samples with known result were evaluated. Pool CT was generally higher than individual samples. Lucigen extraction showed higher CT, including false negative results for samples with high CT at Qiagen extraction. Paired Swab and TW samples showed comparable results. No volunteer from negative pools reported any symptom in the 2-3 days after collection.ConclusionsClinical samples pooling to detect SARS-CoV-2 RNA is feasible and an economical way to test for COVID-19, especially in surveillance strategies targeting more infectiousness, higher viremia individuals. The use of Lucigen reagents show lower sensibility that may lead to false negative results with lower viremia samples. Combining throat wash with saliva may provide and interesting self-collection alternative, but more comparative work is needed.

scholarly journals Limitations of rapid serological testing for SARS-CoV-2 in non-vaccinated patients in acute cardiac care

2021 ◽  
Vol 2 (3) ◽  
pp. 302-305
Author(s):  
Mihajlo Viduljević ◽  
Marija Polovina ◽  
Milika Ašanin ◽  
Igor Mrdović
Keyword(s):  
False Negative ◽  
Immunological Response ◽  
Cardiac Care ◽  
Cardiovascular Disorders ◽  
Serological Testing ◽  
Serological Tests ◽  
Negative Results ◽  
Global Pandemic ◽  
False Negative Results ◽  
The City

In December 2019 in the city of Wuhan, in China, the first cases of infection caused by the new SARS-CoV-2 virus appeared, and later on, the disease caused by this virus was named COVID-19. Shortly after this, on March 11 th , 2020, the WHO characterized COVID-19 as a global pandemic. The symptoms of COVID-19 and acute cardiovascular disorders (e.g., heart failure, pulmonary embolism or myocardial ischemia) frequently overlap, which poses a challenge for the establishing of a differential diagnosis in clinical practice. Rapid serological tests, which detect IgM and IgG classes of antibodies for SARS-CoV 2, have been developed with the primary purpose of screening the population's immunological response to the SARS-CoV-2 virus. However, rapid serological tests are often used outside their original purpose, i.e., for the triage of possibly infected, non-vaccinated individuals, because they offer quick results, which may be particularly relevant in emergency settings. If serological testing is used to guide the admission of non-vaccinated patients with acute cardiovascular disorders to either an isolation unit for suspected COVID-19 positive individuals, or to hospital facilities for non-infected patients, it is important to recognize its limitations, in order to reduce the risk of false-positive or false-negative results. Hence, appropriate patient selection and cautious test interpretation is necessary to avoid misdiagnosis. The aim of this paper is to illustrate how serological testing may be used as a screening tool to inform the management of non-vaccinated patients with acute cardiovascular disorders requiring urgent hospital admission. As an illustration, we describe two clinical situations, in which serological testing produced meaningful results.

scholarly journals Identification of etiological agents of selected bacterial and viral infections based on serological tests

2018 ◽  
Vol 72 ◽  
pp. 1162-1178
Author(s):  
Aleksandra Lewandowicz-Uszyńska ◽  
Piotr Naporowski ◽  
Gerard Pasternak ◽  
Danuta Witkowska
Keyword(s):  
False Positive ◽  
Cellular Response ◽  
Bacterial Infections ◽  
Viral Infections ◽  
False Negative ◽  
Main Role ◽  
Serological Tests ◽  
Negative Results ◽  
False Negative Results ◽  
Positive Results

The human immune system’s response to infection is closely related with the type of pathogen. First, a rapid, metabolically inexpensive and non-specific innate immunity is induced, then a specific acquired immunity is activated. In bacterial infections caused by intracellular pathogens, the main role is played by cellular response. In infections caused by bacterial extracellular pathogens, a crucial role is played by antibodies. The clinical symptoms of bacterial and viral infections very often are similar, which is why diagnosing them based only on medical history and physical examination is insufficient. To identify the etiological factors of infections differentiating media, biochemical tests, molecular methods and serological tests are used. The detection of microorganisms or their genetic material can be performed within a short time after the occurrence of an infection. The detection of antibodies is possible only in the appropriate time called the serological window. In a serological diagnostic of infections there are problems with an appropriate interpretation of obtained results. Cross-reactivity can give false positive results for the diagnosis of Chlamydophila pneumonia infection. The problem with the detection of Borrelia burgdorferi infection can be caused by a simultaneous coinfection with different spirochetes, syphilis, mononucleosis or HIV. In serological diagnostics of bacterial infections, the administration of antibiotics to patients before taking serum samples can be responsible for false negative results. Another reason for such results can be a weak humoral response in infected patients. In viral infections, false positive results can be caused by a coinfection of different viruses, especially from the same family or by bacterial or protozoal coinfections or by autoimmune diseases. False-negative results in viral infections often are caused by the early phase of an infection. To properly recognize an etiological factor of infection it is necessary to use an appropriate method, precision of test and collect samples at the appropriate time.

scholarly journals Impact of false negative results of RT-PCR test for SARS-CoV-2 in COVID-19 case count as applied to Mexico

2020 ◽  
Author(s):  
Isaac J. Núñez ◽  
Pablo F. Belaunzarán-Zamudio ◽  
Yanink Caro-Vega
Keyword(s):  
False Negative ◽  
Open Data ◽  
Clinical Samples ◽  
Rt Pcr ◽  
Negative Results ◽  
Case Count ◽  
False Negative Results ◽  
True Number ◽  
High Prevalence ◽  
Polymerase Chain

Underestimation of the number of cases during the COVID-19 pandemic has been a constant concern worldwide. Case confirmation is based on identification of SARS-CoV-2 RNA using real time polymerase chain reaction (RT-PCR) in clinical samples. However, these tests have suboptimal sensitivity, especially during the early and late course of infection. Using open data, we estimated that among 1 343 730 people tested in Mexico since February 27th, there were 838 377 (95% CL 734 605 - 1 057 164) cases, compared with 604 376 considering only positive tests. ICU admissions and deaths were around 16% and 9% higher than reported. Thus, we show that accounting for the sensitivity of SARS-Cov-2 RT-PCR diagnostic tests is a simple way to improve estimations for the true number of COVID-19 cases in tested people, particularly in high-prevalence populations. This could aid to better inform public health measures and reopening policies.

Three highly sensitive "bedside" serum and urine tests for pregnancy compared

1990 ◽  
Vol 36 (9) ◽  
pp. 1686-1688 ◽  
Author(s):  
H Christensen ◽  
H H Thyssen ◽  
O Schebye ◽  
A Berget
Keyword(s):  
Paired Comparison ◽  
False Negative ◽  
Diagnostic Sensitivity ◽  
Enzyme Linked Immunosorbent Assay ◽  
Serum Samples ◽  
Negative Results ◽  
False Negative Results ◽  
Significant Difference ◽  
Comparison Of The Results ◽  
Urine And Serum

Abstract We examined three enzyme-linked immunosorbent assay (ELISA) kits for human choriogonadotropin (hCG) (pregnancy tests) for use with urine and serum samples: the Tandem Icon II hCG Urine and Tandem Icon II hCG Serum, the NovoClone Target hCG Test, and the Abbott TestPacks hCG-urine and hCG-serum. Paired comparison of the results from each kit indicated that the NovoClone Target assay showed significantly lower diagnostic sensitivity (P less than 0.05) than did the Tandem Icon II or Abbott TestPack, both for urine and for serum samples. None of the products demonstrated any significant difference (P greater than 0.05) in diagnostic specificity, but the NovoClone Target kit showed several serious false-negative results with both urine and serum. Paired testing of urine kits vs serum kits also showed no significant differences (P greater than 0.05) in diagnostic sensitivity or specificity. We found the Abbott kits to be the most convenient to use and to read.

scholarly journals Trueness evaluation and verification of inter-assay agreement of serum folate measuring systems

2020 ◽  
Vol 58 (10) ◽  
pp. 1697-1705
Author(s):  
Federica Braga ◽  
Erika Frusciante ◽  
Simona Ferraro ◽  
Mauro Panteghini
Keyword(s):  
False Negative ◽  
Serum Folate ◽  
Clinical Samples ◽  
Measuring Systems ◽  
Negative Results ◽  
False Negative Results ◽  
Performance Specifications ◽  
The Mean ◽  
Intercomparison Study ◽  
Is Value

AbstractBackgroundDefinitive data to establish if the use of the WHO International Standard (IS) 03/178 as a common calibrator of commercial measuring systems (MSs) has improved the harmonization of serum total folate (tFOL) measurements to a clinically suitable level are lacking. Here, we report the results of an intercomparison study aimed to verify if the current inter-assay variability is acceptable for clinical application of tFOL testing.MethodsAfter confirming their commutability, the IS 03/178 and National Institute for Standards and Technology SRM 3949 L1 were used for evaluating the correctness of traceability implementation by manufacturers and the MSs trueness, respectively. The inter-assay agreement was verified using 20 patient pools. The measurement uncertainty (U) of tFOL measurements on clinical samples was also estimated. An outcome-based model for defining desirable performance specifications for bias and imprecision for serum tFOL measurements was applied.ResultsThe majority of evaluated MSs overestimated the WHO IS value of +5% or more with the risk to produce an unacceptably high number of false-negative results in clinical practice. The mean inter-assay CV on all pools and on those with tFOL values >3.0 μg/L (n = 15) was 12.5% and 7.1%, respectively. In neither case the goal of 3.0% was fulfilled. The residual bias resulted in an excessive U of tFOL measurement on clinical samples.ConclusionsThe implementation of traceability of tFOL MSs to the WHO IS 03/178 is currently inadequate, resulting in an inter-assay variability that does not permit the use of a common threshold for detecting folate deficiency.

scholarly journals Soft Salt-Mannitol Agar–Cloxacillin Test: a Highly Specific Bedside Screening Test for Detection of Colonization with Methicillin-Resistant Staphylococcus aureus

1998 ◽  
Vol 36 (4) ◽  
pp. 986-989 ◽  
Author(s):  
Nuria Mir ◽  
Miguel Sánchez ◽  
Fernando Baquero ◽  
Blanca López ◽  
Celia Calderón ◽  
...  
Keyword(s):  
Intensive Care Unit ◽  
Staphylococcus Aureus ◽  
Intensive Care ◽  
Predictive Value ◽  
Color Change ◽  
False Negative ◽  
Clinical Samples ◽  
Methicillin Resistant ◽  
Negative Results ◽  
False Negative Results

The early detection of colonization with methicillin-resistantStaphylococcus aureus (MRSA) of patients in intensive-care units is an essential step in the strategy for preventing MRSA epidemics. In this study, tubes containing soft salt-mannitol agar with cloxacillin (6 μg/ml) (SSMAC) were prepared for inoculation of clinical samples at patients’ bedsides by personnel of an intensive-care unit. A total of 1,914 swabs from different sample sites of 81 patients were dipped into SSMAC tubes, and after 24 h of incubation (in an incubator located near the intensive-care unit), an evident color change was considered by the intensive-care-unit personnel to be an MRSA alarm. Sixty-three (3.3%) SSMAC tubes were considered positive for MRSA, 1,827 (95.4%) were considered negative, and 24 (1.2%) were considered intermediate. Compared with values for parallel conventional surveillance cultures for MRSA, excluding tubes with intermediate results, the SSMAC test had a sensitivity of 72.7%, a specificity of 99.2%, a positive predictive value of 76.2%, and a negative predictive value of 99.0%. When intermediate tubes were considered positive, the corresponding values were 75.3, 98.2, 63.2, and 99.0%, respectively. The sensitivity and specificity values of the test to identify MRSA-colonized patients were 89.4 and 100%, respectively. Oropharyngeal and naris specimens were the most reliable samples for MRSA detection. False-negative results were frequent in bronchial aspirates with low (<103 to 106CFU/ml) MRSA counts. False-positive results were mainly due to methicillin-resistant Staphylococcus haemolyticus. The SSMAC tube is a useful, rapid, and inexpensive tool for the early identification of MRSA-colonized patients and, consequently, for the implementation of measures to prevent the spread of MRSA.

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