scholarly journals Differential Performance of CoronaCHEK SARS-CoV-2 Lateral Flow Antibody Assay by Geographic Origin of Samples

2021 ◽  
Author(s):  
Owen R. Baker ◽  
M. Kate Grabowski ◽  
Ronald M. Galiwango ◽  
Aminah Nalumansi ◽  
Jennifer Serwanga ◽  
...  
Keyword(s):  
False Positive ◽  
Geographic Origin ◽  
Febrile Illness ◽  
Lateral Flow ◽  
False Positive Test ◽  
Assay Performance ◽  
History Of ◽  
The Impact ◽  
Prevalence Ratios ◽  
Positive Results

Background: We assessed the performance of CoronaCHEK lateral flow assay on samples from Uganda and Baltimore to determine the impact of geographic origin on assay performance. Methods: Plasma samples from SARS-CoV-2 PCR+ individuals (Uganda: 78 samples from 78 individuals and Baltimore: 266 samples from 38 individuals) and from pre-pandemic individuals (Uganda 1077 and Baltimore 532) were evaluated. Prevalence ratios (PR) were calculated to identify factors associated with a false-positive test. Results: After first positive PCR in Ugandan samples the sensitivity was: 45% (95% CI 24,68) at 0-7 days; 79% (95%CI 64,91) 8-14 days; and 76% (95%CI 50,93) >15 days. In samples from Baltimore, sensitivity was: 39% (95% CI 30, 49) 0-7 days; 86% (95% CI 79,92) 8-14 days; and 100% (95% CI 89,100) 15 days post positive PCR. The specificity of 96.5% (95% CI 97.5,95.2) in Ugandan samples was significantly lower than samples from Baltimore 99.3% (95% CI 98.1,99.8), p<0.01. In Ugandan samples, individuals with a false positive result were more likely to be male (PR 2.04, 95% CI 1.03,3.69) or individuals who had a fever more than a month prior to sample acquisition (PR 2.87, 95% CI 1.12,7.35). Conclusions: Sensitivity of the CoronaCHEK was similar in samples from Uganda and Baltimore. The specificity was significantly lower in Ugandan samples than in Baltimore samples. False positive results in Ugandan samples appear to correlate with a recent history of a febrile illness, potentially indicative of a cross-reactive immune response in individuals from East Africa.

scholarly journals Differential Performance of CoronaCHEK SARS-CoV-2 Lateral Flow Antibody Assay by Geographic Origin of Samples

2021 ◽  
Author(s):  
Owen R Baker ◽  
M. Kate Grabowski ◽  
Ronald M Galiwango ◽  
Aminah Nalumansi ◽  
Jennifer Serwanga ◽  
...  
Keyword(s):  
False Positive ◽  
Geographic Origin ◽  
Febrile Illness ◽  
Lateral Flow ◽  
Serum Samples ◽  
False Positive Test ◽  
Assay Performance ◽  
History Of ◽  
The Impact ◽  
Prevalence Ratios

Background: We assessed the performance of CoronaCHEK lateral flow assay on samples from Uganda and Baltimore to determine the impact of geographic origin on assay performance. Methods: Serum samples from SARS-CoV-2 PCR+ individuals (Uganda: 78 samples from 78 individuals and Baltimore: 266 samples from 38 individuals) and from pre-pandemic individuals (Uganda 1077 and Baltimore 532) were evaluated. Prevalence ratios (PR) were calculated to identify factors associated with a false-positive test. Results: After first positive PCR in Ugandan samples the sensitivity was: 45% (95% CI 24,68) at 0-7 days; 79% (95%CI 64,91) 8-14 days; and 76% (95%CI 50,93) >15 days. In samples from Baltimore, sensitivity was: 39% (95% CI 30, 49) 0-7 days; 86% (95% CI 79,92) 8-14 days; and 100% (95% CI 89,100) 15 days post positive PCR. The specificity of 96.5% (95% CI 97.5,95.2) in Ugandan samples was significantly lower than samples from Baltimore 99.3% (95% CI 98.1,99.8), p<0.01. In Ugandan samples, individuals with a false positive result were more likely to be male (PR 2.04, 95% CI 1.03,3.69) or individuals who had a fever more than a month prior to sample acquisition (PR 2.87, 95% CI 1.12,7.35). Conclusions: Sensitivity of the CoronaCHEK was similar in samples from Uganda and Baltimore. The specificity was significantly lower in Ugandan samples than in Baltimore samples. False positive results in Ugandan samples appear to correlate with a recent history of a febrile illness, potentially indicative of a cross-reactive immune response in individuals from East Africa.

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

scholarly journals SAT-192 Eletriptan (RelpaxaTm) Causing False Positive Elevations in Urinary Metanephrine

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Zachary Bloomer ◽  
Nath Priti ◽  
Thanh Duc Hoang ◽  
Mohamed K M Shakir
Keyword(s):  
Blood Pressure ◽  
False Positive ◽  
Arterial Blood Flow ◽  
Positive Test ◽  
Uncontrolled Hypertension ◽  
False Positive Test ◽  
Arterial Blood ◽  
History Of ◽  
Plasma Metanephrines ◽  
Urine Metanephrines

Abstract Background: The diagnosis of pheochromocytoma depends crucially on the demonstration of excessive production of catecholamines. This step, however, is fraught with several difficulties, in particular with false-positive test results. Drugs such as phenoxybenzamine and tricyclic antidepressants are the most frequently associated causes for false-positive results. Other medications are also known to cause a false positive elevation of urinary metanephrines. We are reporting a patient with markedly elevated urine metanephrines associated with the use of Eletriptan hydrobromide (RelpaxaTM), a drug commonly used for treating migraine. Clinical Case: A 29-year-old man with a history of migraine managed on ibuprofen and recently started Eletriptan presented to the emergency room complaining of a 24-hour history of progressively worsening headaches. At the time of initial evaluation his blood pressure was in the 220s/160s with a creatinine of 1.9 mg/dL with unknown baseline. He was managed on an IV nicardipine drip. Due to his young age he underwent an evaluation for secondary causes of his hypertension. Laboratory: normal aldosterone/renin level (ratio was 0.4), normal midnight salivary cortisol and normal thyroid function studies. Urine screening for drug abuse was also negative. A 24-hour urine metanephrine level, while the patient was taking Eletriptan, was markedly elevated (normetanephrine 1341mcg (ref 82–500) and metanephrine level of 2494 mcg (ref 45–290). In contrast, the plasma metanephrines were only mildly elevated (metanephrines level 27 pg/ml (ref 0–62) and normetanephrine level of 255 pg/ml (ref 0–145)). Adrenal CT did not reveal any evidence of adrenal nodules. Additionally a Gallium-68 PET/CT scan did not reveal any evidence of pheochromocytoma or paraganglioma. Eletriptan was discontinued and his blood pressure was controlled on oral medications. Within one week of stopping Eletriptan his urine metanephrines (metanephrine 76 mcg/ 24 hrs, normetanephrine 277 mcg/dL) and plasma metanephrines (metanephrine 39 pg/mL, normetanephrine 148 pg/mL) normalized. Conclusion: The discrepancy between plasma and urine metanephrines in our patient suggests the possibility of a false positive test. Eletriptan, a second generation triptan drug, is a selective 5-hydroxytryptamine 1B/1D receptor agonist and has been shown to reduce carotid arterial blood flow, with only a small increase in arterial blood pressure at high doses. However, Eletriptan has no significant affinity or pharmacological activity at adrenergic α1, α2, or β; dopaminergic D1 or D2; muscarinic; or opioid receptors. It is also interesting to note that Eletriptan use is contraindicated in uncontrolled hypertension. It is possible Eletriptan may affect the assay of urine metanephrines. However, the exact mechanism of Eletriptan causing elevated urine metanephrines in our patient is not clear.

Incidence of False-Positive Results for Assays Used To Detect Antibiotics in Milk

1996 ◽  
Vol 59 (8) ◽  
pp. 886-888 ◽  
Author(s):  
LISA W. HALBERT ◽  
RONALD J. ERSKINE ◽  
PAUL C. BARTLETT ◽  
GILBERT L. JOHNSON
Keyword(s):  
Somatic Cell ◽  
Cell Count ◽  
False Positive ◽  
Somatic Cell Count ◽  
Antimicrobial Agents ◽  
Antimicrobial Treatment ◽  
Milk Samples ◽  
Test Kit ◽  
History Of ◽  
Positive Results

The incidence of false-positive results from milk assays for antimicrobial agents was determined for composite milk samples collected from 407 lactating dairy cows with a history of no antibiotic treatment for a minimum of 30 days. Milk samples were also cultured for bacteria and analyzed for somatic cell count. Mean herd prevalence of intramammary infections (±SEM) caused by Streptococcus agalactiae and Staphylococcus aureus was 3.3 ± 2.8 and 20.2 ± 9.5% of lactating cows, respectively. All 407 milk samples were assayed for antibiotics with three commercial tests; a fourth test was used to assay 391 samples. Samples were assayed twice with each test, and if the results from these repetitions did not agree, a third assay was performed and the result obtained in two of the three repetitions was reported. Because samples were only collected from cows with no antimicrobial treatment for a minimum of 30 days, positive assays were considered to be false-positive results. Three test kits did not yield any false-positive results, one test kit had 5 false-positive results of 407 samples collected (specificity, 98.8%). Although there was a trend for false-positive samples to have a higher somatic cell count than negative samples, the low incidence of false-positive results did not allow a meaningful comparison. We conclude that the incidence of false-positive results is very low when testing milk from cows that have a history of no clinical mastitis or antimicrobial treatment.

scholarly journals To assemble or not to resemble—A validated Comparative Metatranscriptomics Workflow (CoMW)

GigaScience ◽  
2019 ◽  
Vol 8 (8) ◽  
Author(s):  
Muhammad Zohaib Anwar ◽  
Anders Lanzen ◽  
Toke Bang-Andreasen ◽  
Carsten Suhr Jacobsen
Keyword(s):  
Real World ◽  
False Positive ◽  
De Novo Assembly ◽  
De Novo ◽  
Reference Database ◽  
Terrestrial Environments ◽  
Real World Datasets ◽  
External Stimuli ◽  
The Impact ◽  
Positive Results

Abstract Background Metatranscriptomics has been used widely for investigation and quantification of microbial communities’ activity in response to external stimuli. By assessing the genes expressed, metatranscriptomics provides an understanding of the interactions between different major functional guilds and the environment. Here, we present a de novo assembly-based Comparative Metatranscriptomics Workflow (CoMW) implemented in a modular, reproducible structure. Metatranscriptomics typically uses short sequence reads, which can either be directly aligned to external reference databases (“assembly-free approach”) or first assembled into contigs before alignment (“assembly-based approach”). We also compare CoMW (assembly-based implementation) with an assembly-free alternative workflow, using simulated and real-world metatranscriptomes from Arctic and temperate terrestrial environments. We evaluate their accuracy in precision and recall using generic and specialized hierarchical protein databases. Results CoMW provided significantly fewer false-positive results, resulting in more precise identification and quantification of functional genes in metatranscriptomes. Using the comprehensive database M5nr, the assembly-based approach identified genes with only 0.6% false-positive results at thresholds ranging from inclusive to stringent compared with the assembly-free approach, which yielded up to 15% false-positive results. Using specialized databases (carbohydrate-active enzyme and nitrogen cycle), the assembly-based approach identified and quantified genes with 3–5 times fewer false-positive results. We also evaluated the impact of both approaches on real-world datasets. Conclusions We present an open source de novo assembly-based CoMW. Our benchmarking findings support assembling short reads into contigs before alignment to a reference database because this provides higher precision and minimizes false-positive results.

scholarly journals The Impact of Universal Transport Media and Viral Transport Media Liquid Samples on a SARS-CoV-2 Rapid Antigen Test

2021 ◽  
Author(s):  
Jeff Mayfield ◽  
Peter Hesse ◽  
David Ledden
Keyword(s):  
Ionic Strength ◽  
False Positive ◽  
Antigen Test ◽  
Liquid Samples ◽  
Viral Transport ◽  
Extraction Buffer ◽  
High Concentrations ◽  
Low Ionic Strength ◽  
The Impact ◽  
Positive Results

The impact of universal transport media (UTM) and viral transport media (VTM) liquid samples on the performance of the Healgen Scientific Rapid COVID-19 Antigen Test was investigated. Twelve different UTM/VTM liquid samples were added at different dilutions to the extraction buffer, and 2 of 12 generated false-positive results. To understand the cause of these false-positive results, the effect of extraction buffer dilution on sample pH, surfactant concentration, and ionic strength were investigated. The most important factor in UTM/VTM liquid sample dilution of the extraction buffer was ionic strength as measured by conductivity. Dilutions with conductivity below ~17 mS/cm can induce a false-positive result. It was also noted that the ionic strength of UTM/VTMs can vary, and those with low ionic strength can be problematic. To rule out the effect of other common components found in UTMs/VTMs, several materials were mixed with extraction buffer and tested at high concentrations. None was shown to produce false-positive results.

False-positive results for ketone with the drug mesna and other free-sulfhydryl compounds.

1987 ◽  
Vol 33 (2) ◽  
pp. 289-292 ◽  
Author(s):  
G Csako
Keyword(s):  
Acetic Acid ◽  
False Positive ◽  
Glacial Acetic Acid ◽  
Ketone Bodies ◽  
The Other ◽  
False Positive Test ◽  
Red Color ◽  
Sh Group ◽  
Sulfhydryl Compounds ◽  
Positive Results

Abstract All free-sulfhydryl compounds tested produced false-positive reactions in the Legal test for ketones. The color developed in the ketone pad of urine dipsticks [N-Multistix SG, Multistix 10 SG (Ames), and Chemstrip 9 (Boehringer-Mannheim)] was misinterpreted for ketone bodies, both by visual and automated reading. In contrast to the reaction with true ketones, a drop of glacial acetic acid added onto the ketone pad of dipsticks discharged the false-positive red color. A red-violet also developed instantly with free -SH compounds in the Acetest tablet assay (Ames), but quickly faded. In general, the presence of acidic groups such as -COOH and -SO3H in the structure appeared to increase the nitroprusside reactivity of free -SH compounds, whereas the presence of a -NH2 group appeared to decrease it. Currently, false-positive ketone reactions ascribable to a free -SH group are most likely to be seen for urine containing mesna. The false-positive test for ketones caused by free -SH compounds can be recognized and ruled out by proper procedures. On the other hand, this chromogenic reaction with free thiols might be used for monitoring urinary excretion of mesna.

Selective Use of Intraoperative Touch Prep Analysis of Sentinel Nodes in Breast Cancer

2005 ◽  
Vol 71 (11) ◽  
pp. 955-962 ◽  
Author(s):  
Rachel C. Forbes ◽  
Clovis Pitchford ◽  
Jean F. Simpson ◽  
Glen C. Balch ◽  
Mark C. Kelley
Keyword(s):  
Breast Cancer ◽  
Predictive Value ◽  
False Positive ◽  
False Negative ◽  
Nodal Metastasis ◽  
Axillary Lymph ◽  
Sentinel Nodes ◽  
Number Of Patients ◽  
The Impact ◽  
Positive Results

Imprint cytology (touch prep) is often used for intraoperative examination of sentinel nodes in breast cancer. This allows axillary lymph node dissection (ALND) to be performed immediately for tumor-positive nodes. We evaluated the accuracy of touch prep examination of sentinel nodes and its role in the surgical treatment of breast cancer. We analyzed 169 breast cancer patients who underwent 170 lymphatic mapping procedures with intraoperative touch prep examination. Results from the touch prep were correlated with histopathology and clinical variables. There were 115 true-negative, 35 true-positive, 15 false-negative, and 5 false-positive results. Touch prep had a sensitivity of 70 per cent and specificity of 96 per cent. Positive predictive value, negative predictive value, and diagnostic accuracy were all 88 per cent. The false-negative rate was 30 per cent and correlated with the size of the nodal metastasis and number of involved nodes, but not other patient factors. Touch prep is useful for the evaluation of sentinel nodes in breast cancer, but it has a lower sensitivity than initially reported, particularly in patients with micrometastases. False positive results occur, although they may be reduced after experience with the technique. We recommend that suspicious findings on touch prep should be confirmed by frozen section and that ALND only be performed for histologically documented metastases. We currently perform touch prep only in patients who are at high risk of nodal metastasis or will undergo mastectomy. This improves operative efficiency and limits the impact of false positive and negative results without dramatically increasing the number of patients who require a second surgical procedure.

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