scholarly journals A mathematical model of the in vitro micronucleus assay predicts false negative results if micronuclei are not specifically scored in binucleated cells or in cells that have completed one nuclear division

Mutagenesis ◽  
2000 ◽  
Vol 15 (4) ◽  
pp. 329-336 ◽  
Author(s):  
M. Fenech
Keyword(s):  
Mathematical Model ◽  
Nuclear Division ◽  
False Negative ◽  
Micronucleus Assay ◽  
Negative Results ◽  
Binucleated Cells ◽  
False Negative Results ◽  
In Vitro Micronucleus Assay ◽  
In Cells

Aspiration Revisited: Prospective Evaluation of a Physiologically Pressurized Model With Animal Correlation and Broader Applicability to Filler Complications

2021 ◽  
Author(s):  
Hyoung-Jin Moon ◽  
Won Lee ◽  
Ji-Soo Kim ◽  
Eun-Jung Yang ◽  
Hema Sundaram
Keyword(s):  
Normal Saline ◽  
False Negative ◽  
Vascular Complications ◽  
Filler Injection ◽  
Negative Results ◽  
Needle Position ◽  
False Negative Results ◽  
In Vivo Testing

Abstract Background Aspiration testing before filler injection is controversial. Some believe that aspiration can help prevent inadvertent intravascular injection, while others cite false-negative results and question its value given that the needle position always changes somewhat during injection procedures. Objectives To test the relation of false-negative results to the viscosity of the material within the needle lumen and determine whether a less viscous material within the needle lumen could decrease the incidence of false-negative results. Methods In vitro aspiration tests were performed using 30-G and 27-G needle gauges, two cross-linked hyaluronic acid fillers, normal saline bags pressurized at 140 and 10 mmHg to mimic human arterial and venous pressures, and three needle lumen conditions (normal saline, air, and filler). Testing was repeated three times under each study condition (72 tests in total). For in vivo correlation, aspiration tests were performed on femoral arteries and central auricular veins in three rabbits (4–5 aspirations per site, 48 tests in total). Results In vitro and in vivo testing using 30-G needles containing filler both showed false-negative results on aspiration testing. In vitro and in vivo testing using needles containing saline or air showed positive findings. Conclusions False-negative results from aspiration testing may be reduced by pre-filling the needle lumen with saline rather than a filler. The pressurized system may help overcome challenges of animal models with intravascular pressures significantly different from those of humans. The adaptability of this system to mimic various vessel pressures may facilitate physiologically relevant studies of vascular complications.

False-negative results for urinary phenothiazines and imipramine in Forrest's qualitative assays.

1980 ◽  
Vol 26 (2) ◽  
pp. 345-347 ◽  
Author(s):  
G P James ◽  
M H DJang ◽  
H H Hamilton
Keyword(s):  
Ascorbic Acid ◽  
Ion Exchange ◽  
Exchange Resin ◽  
Anion Exchange Resin ◽  
False Negative ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Negative Results ◽  
False Negative Results

Abstract When a series of patients' urine samples supplemented in vitro with chlorpromazine or imipramine was assayed with the Forrest qualitative assays, we observed an occasional false-negative result, which we found was attributable to interference by ascorbic acid. It interferes with the reagent, not with the analytes, in both assays. We easily eliminated this interference with the phenothiazine test by using an anion-exchange resin. Eliminating the interference with the assay for imipramine, however, is more difficult; false-negative results can be obtained even after ion-exchange chromatography if the imipramine concentration is less than 50 mg/L.

False-negative results for urinary phenothiazines and imipramine in Forrest's qualitative assays.

1980 ◽  
Vol 26 (2) ◽  
pp. 345-347
Author(s):  
G P James ◽  
M H DJang ◽  
H H Hamilton
Keyword(s):  
Ascorbic Acid ◽  
Ion Exchange ◽  
Exchange Resin ◽  
Anion Exchange Resin ◽  
False Negative ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Negative Results ◽  
False Negative Results

Abstract When a series of patients' urine samples supplemented in vitro with chlorpromazine or imipramine was assayed with the Forrest qualitative assays, we observed an occasional false-negative result, which we found was attributable to interference by ascorbic acid. It interferes with the reagent, not with the analytes, in both assays. We easily eliminated this interference with the phenothiazine test by using an anion-exchange resin. Eliminating the interference with the assay for imipramine, however, is more difficult; false-negative results can be obtained even after ion-exchange chromatography if the imipramine concentration is less than 50 mg/L.

scholarly journals Evaluating the Cost-Effectiveness of Proposed Algorithms for C. difficile Infection in Different Pretest Probability Settings

2020 ◽  
Vol 41 (S1) ◽  
pp. s224-s225
Author(s):  
Mirian Dal Ben ◽  
Maura Oliveira ◽  
Paola Cappellano ◽  
Jorge Sampaio ◽  
Maria Beatriz Dias
Keyword(s):  
Mathematical Model ◽  
Cost Effectiveness ◽  
Positive Result ◽  
False Positive ◽  
Annual Cost ◽  
False Negative ◽  
Pretest Probability ◽  
Negative Results ◽  
False Negative Results ◽  
The Cost

Background: The use of real-time polymerase chain reaction (RT-PCR) as a first-line test for the diagnosis of Clostridioides difficile may result in overdiagnosis and overtreatment because the test is not capable of distinguishing infection from carriage. Toxin EIA assays have impeditive low sensitivity. Some algorithms using enzyme immunoassay for glutamate dehydrogenase (GDH) antigen and toxins A and B as the first step have been proposed to increase diagnostic performance. However, cost-effectiveness of different diagnostic algorithms would depend on the cost of each test and on the pretest probability in different settings. The objective of the present study was to evaluate the cost-effectiveness of 2 algorithms proposed by current guidelines to diagnose C. difficile infection by developing a mathematical model that would take into account the epidemiology and costs in our hospital. Methods: The study was conducted in a 480-bed tertiary-care teaching hospital in So Paulo, Brazil. All suspected C. difficile infection cases from January to December of 2017 were evaluated for pretest probability analysis. All stools collected from patients with a requested PCR test for suspected C. difficile infection were selected for additional testing to measure the specificity and sensitivity of each different test: C. diff GDH/Toxin A/B combined test, Toxin A/B Microplate Assay, GDH, and PCR. Toxigenic stool culture for C. difficile was considered the gold standard. A mathematical model was developed and simulations were done. The outcomes evaluated were: final annual costs with diagnostic tests in US dollars and number of patients receiving a false-positive or a false-negative diagnosis in a year simulation. Results: In total, 1,441 stool samples were tested by PCR for C. difficile in our institution from January 2017 to December 2017. Overall, 206 had a positive result, with a pretest probability of 14.3%. In our simulations, the PCR-based algorithm had an annual cost of US$279,914.25, with 4 false-negative results and 8 false-positive results. The implementation of a GDH/Toxin/PCR stepwise algorithm would have reduced the annual cost to US$160,488.75, with 6 false-negative results and 1 false-positive result. Simulations of annual cost and performance of the 2 algorithms have shown that the stepwise algorithm would still be advantageous in settings with higher pretest probabilities (Fig. 1). Conclusions: A stepwise algorithm based on GDH/Toxin before PCR seems to be more cost-effective, even in settings with higher pretest probabilities.Funding: NoneDisclosures: None

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.

Scoring System for the Diagnosis of COVID-19

2020 ◽  
Vol 13 (1) ◽  
pp. 413-414 ◽  
Author(s):  
Mohamed Farouk Allam
Keyword(s):  
Scoring System ◽  
Clinical Symptoms ◽  
False Negative ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Negative Results ◽  
False Negative Results ◽  
Symptoms And Signs

Due to the international spread of COVID-19, the difficulty of collecting nasopharyngeal swab specimen from all suspected patients, the costs of RT-PCR and CT, and the false negative results of RT-PCR assay in 41% of COVID-19 patients, a scoring system is needed to classify the suspected patients in order to determine the need for follow-up, home isolation, quarantine or the conduction of further investigations. A scoring system is proposed as a diagnostic tool for suspected patients. It includes Epidemiological Evidence of Exposure, Clinical Symptoms and Signs, and Investigations (if available). This scoring system is simple, could be calculated in a few minutes, and incorporates the main possible data/findings of any patient.

Detection of Streptococcus pneumoniae in Sputum Samples by Real- Time PCR.

2020 ◽  
Vol 18 ◽  
Author(s):  
Pegah Shakib ◽  
Mohammad Reza Zolfaghari
Keyword(s):  
Streptococcus Pneumoniae ◽  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Cross Sectional Study ◽  
Laboratory Culture ◽  
Cross Sectional ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Method

Background: Conventional laboratory culture-based methods for diagnosis of Streptococcus pneumoniae are time-consuming and yield false negative results. Molecular methods including real-time (RT)-PCR rapid methods and conventional PCR due to higher sensitivity and accuracy have been replaced instead traditional culture assay. The aim of the current study was to evaluate lytA gene for detection of Streptococcus pneumoniae in the cerebrospinal fluid of human patients with meningitis using real-time PCR assay. Material and Methods: In this cross-sectional study, a total of 30 clinical specimens were collected from patients in a period from September to December 2018. In order to evaluate the presence of lytA gene, conventional and real-time PCR methods were used without culture. Results: From 30 sputum samples five (16.66%) isolates were identified as S. pneumoniae by lytA PCR and sequencing. Discussion: In this research, an accurate and rapid real-time PCR method was used, which is based on lytA gene for diagnosis of bacteria so that it can be diagnosed. Based on the sequencing results, the sensitivity for detection of lytA gene was 100% (5/5).

COVID-19: how nuclear medicine can provide a differential diagnosis in very dubious case

Coronaviruses ◽  
2020 ◽  
Vol 01 ◽  
Author(s):  
Maria Silvia De Feo ◽  
Viviana Frantellizzi ◽  
Giuseppe De Vincentis
Keyword(s):  
Infectious Disease ◽  
Differential Diagnosis ◽  
Ct Scan ◽  
Imaging Technique ◽  
False Negative ◽  
Clinical Signs ◽  
Negative Results ◽  
Infectious Disease Department ◽  
False Negative Results ◽  
99Mtc Hmpao

Background: We present the case of a 55-year-old woman, admitted to the Infectious Disease Department of Policlinico Umberto I, Rome, in mid-March 2020, with suspicion of COVID-19 infection. Objective: The rRT-PCR was negative and the following CT scan, performed to exclude false-negative results and help diagnosis, was inconclusive. Methods: It was decided to submit the patient to 99mTc-HMPAO-labelled leukocyte scan. Results: This exam led to the diagnosis of infective endocarditis. Conclusion: In the present pandemic scenario, 99mTc-HMPAO-labelled leukocyte scan represents a reliable imaging technique for differential diagnosis with COVID-19 in patients with confusing clinical signs, possible false-negative rRT-PCR results and inconclusive CT scan.

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