A Collaborative Study on the Detection of Staphylococcal Enterotoxins in Foods with an Enzyme Immunoassay Kit (TECRA)

1996 ◽  
Vol 59 (4) ◽  
pp. 390-397 ◽  
Author(s):  
C. E. PARK ◽  
D. WARBURTON ◽  
P. J. LAFFEY ◽  
Keyword(s):  
Enzyme Immunoassay ◽  
False Positive ◽  
Collaborative Study ◽  
False Negative ◽  
Negative Control ◽  
Rabbit Serum ◽  
Staphylococcal Enterotoxins ◽  
Repeatability And Reproducibility ◽  
Positive Results ◽  
Control Samples

One of the commercially available enzyme immunoassay kits for the detection of staphylococcal enterotoxins (SEs) in foods, the TECRA screening kit (Bioenterprises Pty. Ltd., Roseville, New South Wales, Australia), has microtiter plates coated with a mixture of antibodies to all of the SEs. A collaborative study was conducted to ascertain whether specificity, sensitivity, repeatability, and reproducibility of the results obtained using this kit would meet food-safety criteria. Thirteen Canadian collaborators participated in this study to analyze both various foods to which 1.0 to 3.0 ng of SE/g of food had been added and negative control samples. In addition, the effect of animal serum in these analyses was examined. The results indicate that all collaborators (100%) were able to detect the minimum toxin levels of 1.0 ng of SEA/g of ham and 1.0 ng of SEB/g of salami and SE or SEs in other samples (chicken, turkey, and cheese) containing 2.0 to 3.0 ng/g, without any false-negative results. With regard to negative control samples, all collaborators obtained correct results except when analyzing two types of food: two collaborators (15%) showed weak false-positive results with salami and all analysts found strong false-positive results with mussels. The problem regarding specificity could be largely corrected by treating the sample with rabbit serum (0.1 volume in 1.0 volume food extract). The repeatability and reproducibility of results from the kit were acceptable.

scholarly journals The Problem of DNA/RNA Contamination in the Laboratory during PCR Testing for COVID-19

2021 ◽  
pp. 76-81
Author(s):  
AS Volynkina ◽  
AG Ryazanova ◽  
DV Rusanova ◽  
AN Kulichenko
Keyword(s):  
False Positive ◽  
False Negative ◽  
Rna Isolation ◽  
Negative Control ◽  
Laboratory Diagnostics ◽  
Cross Contamination ◽  
Laboratory Service ◽  
Pcr Products ◽  
Rna Contamination ◽  
Control Samples

Introduction. When conducting PCR (polymerase chain reaction) testing of biospecimens for SARS-CoV-2 RNA at the beginning of the COVID-19 pandemic, the laboratory service in Russia and foreign countries encountered problems related to the accuracy of diagnostics and obtaining false negative, false positive, and dubious results. The objective of this work was to analyze current literature on the problem of false positive and dubious results of RT-PCR testing for COVID-19. Material and methods. We selected Russian and foreign English-language publications devoted to organization of laboratory diagnostics of the novel coronavirus disease, challenges of PCR testing for SARS and MERS, and general issues of DNA contamination in a PCR laboratory for 2012–2020. We also reviewed current regulations and guidelines for COVID-19 diagnostic testing. Results. The analysis of factors leading to contamination of specimens with nucleic acids in the laboratories performing massive COVID-19 PCR testing during the pandemic showed that the main reasons for contamination included a large number of tests, accumulation of samples in the laboratory, and the increased amount of wastes containing amplification products. Cross-contamination occurs due to technical errors in the course of laboratory manipulations at the stages of sample preparation and inactivation, RNA isolation, and addition of cDNA/RNA or positive control samples to the reaction mixture. Pollution of laboratory working areas with amplicons arising from the opening of tubes and plates containing PCR products is the main cause of total contamination in the laboratory. Signs of cross-contamination include the increase in the proportion of positive samples with low threshold cycle values and detection of a positive signal from negative control samples at RNA isolation and amplification stages. A positive result for all samples in a round, including negative control samples, is a marker of “total contamination” in the laboratory. In addition to contamination, formation of nonspecific PCR products at late reaction cycles and nonspecific fluorescence of the reaction mixture, which occurs when reagent storage temperatures are not observed, may also lead to false positive results. Conclusion. To prevent contamination in a PCR laboratory, strict control over the flow of test samples and medical wastes, regular analysis of the frequency of positive test results, and mandatory laboratory quality control of testing and DNA/RNA contamination are compulsory.

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.

Three Years of Experience With Random Urinary Homovanillic and Vanillylmandelic Acid Levels in the Diagnosis of Neuroblastoma

PEDIATRICS ◽  
1987 ◽  
Vol 79 (2) ◽  
pp. 203-205
Author(s):  
Mendel Tuchman ◽  
Margaret L. R. Ramnaraine ◽  
William G. Woods ◽  
William Krivit
Keyword(s):  
False Positive ◽  
Homovanillic Acid ◽  
False Negative ◽  
False Negative Rate ◽  
Urine Samples ◽  
Vanillylmandelic Acid ◽  
Test Results ◽  
Upper Limit ◽  
Positive Results ◽  
Rule Out

During the last 3 years, random urine samples from 408 patients were tested for elevated homovanillic acid (HVA) and vanillylmandelic acid (VMA) levels to rule out the diagnosis of neuroblastoma. Thirty-seven of these patients had elevated HVA and/or VMA levels, and neuroblastoma was subsequently diagnosed. In three additional patients with negative test results (normal HVA and VMA levels), tumors were subsequently diagnosed (false-negative rate of 7.5%). Ten percent of the patients with neuroblastoma had normal HVA and 27.5% had normal VMA levels at the time of diagnosis. Only one patient (2.5%) with neuroblastoma had elevated VMA levels in the presence of normal HVA levels. More than 60% of the patients with neuroblastoma had urinary HVA and/or VMA levels higher than twice the upper limit of normal. No false-positive results were encountered. Age and stage distributions of the patients are shown, and the significance of the results is discussed.

N.B.T. TEST—FALSE-NEGATIVE AND FALSE-POSITIVE RESULTS

The Lancet ◽  
1972 ◽  
Vol 299 (7764) ◽  
pp. 1341-1342 ◽  
Author(s):  
RonaldP. Ng ◽  
T.K. Chan ◽  
D. Todd
Keyword(s):  
False Positive ◽  
False Negative ◽  
Positive Results

Low Rate of False-Positive Results with Use of A Rapid HIV Test

2002 ◽  
Vol 23 (6) ◽  
pp. 335-337 ◽  
Author(s):  
Cassandra D. Salgado ◽  
Heidi L. Flanagan ◽  
Doris M. Haverstick ◽  
Barry M. Farr
Keyword(s):  
Enzyme Immunoassay ◽  
False Positive ◽  
Diagnostic System ◽  
Rapid Test ◽  
Occupational Exposures ◽  
High Rate ◽  
Negative Results ◽  
Hiv Test ◽  
Rapid Hiv Test ◽  
Positive Results

Background:Occupational exposure to human immunodeficiency virus (HIV) is an important threat to healthcare workers. Centers for Disease Control and Prevention guidelines recommend prompt institution of prophylaxis. This requires (1) immediate prophylaxis after exposure, pending test results that may take more than 24 hours in many hospitals; or (2) performance of a rapid test. The Single Use Diagnostic System (SUDS)® HIV-1 Test is used to screen rapidly for antibodies to HIV type 1 in plasma or serum, with a reported sensitivity of more than 99.9%. We used this test from January 1999 until September 2000, when it was withdrawn from the market following reports claiming a high rate of false-positive results.Methods:We reviewed the results of postexposure HIV testing during 21 months.Results:A total of 884 SUDS tests were performed on source patients after occupational exposures (883 negative results, 1 reactive result). The results of repeat SUDS testing on the reactive specimen were also reactive, but the results of enzyme immunoassay and Western blot testing were negative. A new specimen from the same patient showed a negative result on SUDS testing. This suggested a specificity of 99.9%. In the 4 months after SUDS testing was suspended, there was 1 false-positive result on enzyme immunoassay for 1 of 132 source patients (presumed specificity, 99.2%).Conclusion:Use of the SUDS test facilitated rapid and accurate evaluation of source specimens, obviating unnecessary prophylaxis.

Thyroid Screening for Early Discharged Infants

PEDIATRICS ◽  
1996 ◽  
Vol 98 (1) ◽  
pp. 41-44
Author(s):  
Judy G. Saslow ◽  
Ernest M. Post ◽  
Carol A. Southard
Keyword(s):  
New Jersey ◽  
Congenital Hypothyroidism ◽  
False Positive ◽  
False Negative ◽  
Negative Results ◽  
Thyroid Screening ◽  
False Negative Results ◽  
Positive Results

Objective. As neonatal discharge before 24 hours of life becomes commonplace, the rejection of congenital hypothyroidism (CH) screening specimens obtained too early has created the need for numerous additional tests. We sought to determine whether the specimens obtained before 24 hours could be used safely. Methods. During a 31-day period we measured thyrotropin in all thyroid-screening specimens that had been obtained before 24 hours. We also examined the early specimens from every infant diagnosed in New Jersey with CH during 1993 or 1994. Results. Among the 663 specimens, those obtained at or before 12 hours and those from infants with birth weights less than 2500 g had too many low thyroxine results to be useful. Among the 515 specimens obtained at more than 12 to 24 hours from newborns weighing 2500 g or more, 37 (7%) had low thyroxine levels and 12 (2.3%) had thyrotropin levels of 20 µIU/mL (mU/L) or higher. Four hundred seventy-one of the 515 infants had subsequent specimens obtained at more than 24 hours, and none of the results were abnormal. There was no child weighing more than or equal to 2500 g who was diagnosed with CH in 1993 and 1994 whose specimen obtained at 24 hours or less was normal. Conclusions. Accepting specimens obtained at more than 12 to 24 hours from infants weighing 2500 g or more would have resulted in more than the usual number of false-positive results but no false-negative results. This would have decreased the requests for additional specimens by more than 90%.

scholarly journals Immunoenzymatic Detection of Staphylococcal Enterotoxins: International Interlaboratory Study

1996 ◽  
Vol 79 (5) ◽  
pp. 1095-1101 ◽  
Author(s):  
Christiane Lapeyre ◽  
Marie-Noelle De Solan ◽  
Xavier Drouet
Keyword(s):  
Enzyme Immunoassay ◽  
Protein A ◽  
Raw Milk ◽  
Interlaboratory Study ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Staphylococcal Enterotoxins ◽  
Raw Milk Cheese ◽  
Culture Supernatants

Abstract An international interlaboratory study was performed by 13 laboratories to validate a commercially available, rapid enzyme immunoassay for detection of staphylococcal enterotoxins A, B, C, D, and E in foods. The 5 enterotoxin serotypes were detected at a level of 0.5 ng/g in mushrooms and ravioli, 0.8 ng/g in meat, 1 ng/mL in milk, and 1.5 ng/g in raw milk cheese when these foods were artificially contaminated with enterotoxin A. Enterotoxins A, B, C, D, or E were also detected in culture supernatants with no protein A interference when normal rabbit serum was used. This method was validated by the French Normalization Agency for the identification of staphylococcal enterotoxins in foods and culture fluids.

scholarly journals Factors associated with false negative and false positive results of prostate-specific antigen (PSA) and the impact on patient health

Medicine ◽  
2019 ◽  
Vol 98 (40) ◽  
pp. e17451 ◽  
Author(s):  
Mari Carmen Bernal-Soriano ◽  
Lucy A. Parker ◽  
Maite López-Garrigos ◽  
Ildefonso Hernández-Aguado ◽  
Juan P. Caballero-Romeu ◽  
...  
Keyword(s):  
Prostate Specific Antigen ◽  
False Positive ◽  
False Negative ◽  
Specific Antigen ◽  
Factors Associated ◽  
Patient Health ◽  
The Impact ◽  
Positive Results
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