Onychomycosis Infections

2017 ◽  
Vol 107 (4) ◽  
pp. 280-286 ◽  
Author(s):  
Aditya K. Gupta ◽  
Kerry-Ann Nakrieko
Keyword(s):  
False Negative ◽  
Kappa Statistic ◽  
False Negatives ◽  
Negative Results ◽  
False Negative Results ◽  
Repeated Sampling ◽  
Polymerase Chain ◽  
Serial Samples ◽  
Repeated Samples ◽  
Infecting Organisms

Background: Mycological culture is the traditional method for identifying infecting agents of onychomycosis despite high false-negative results, slower processing, and complications surrounding nondermatophyte mold (NDM) infections. Molecular polymerase chain reaction (PCR) methods are faster and suited for ascertaining NDM infections. Methods: To measure agreement between culture and PCR methods for identification of infecting species of suspected onychomycosis, single toenail samples from 167 patients and repeated serial samples from 43 patients with suspected onychomycosis were processed by culture and PCR for identification of 16 dermatophytes and five NDMs. Agreement between methods was quantified using the kappa statistic (κ). Results: The methods exhibited fair agreement for the identification of all infecting organisms (single samples: κ = 0.32; repeated samples: κ = 0.38). For dermatophytes, agreement was moderate (single samples: κ = 0.44; repeated samples: κ = 0.42). For NDMs, agreement was poor with single samples (κ = 0.16) but fair with repeated samples (κ = 0.25). Excluding false-negative reports from analyses improved agreement between methods in all cases except the identification of NDMs from single samples. Conclusions: Culture was three or four times more likely to report a false-negative result compared with PCR. The increased agreement between methods observed by excluding false-negative reports statistically clarifies and highlights the major discord caused by false-negative cultures. The increased agreement of NDM identification from poor to fair with repeated sampling along with their poor agreement in the single samples, with and without false-negatives, affirms the complications of NDM identification and supports the recommendation that serial samples help confirm the diagnosis of NDM infections.

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%).

Prevalence of porA pseudogene deletion among Neisseria gonorrhoeae isolates referred to the UK’s Gonococcal Resistance to Antimicrobials Surveillance Program

Sexual Health ◽  
2017 ◽  
Vol 14 (4) ◽  
pp. 392 ◽  
Author(s):  
Martina Toby ◽  
Pamela Saunders ◽  
Michelle Cole ◽  
Vlad Grigorjev ◽  
Sarah Alexander ◽  
...  
Keyword(s):  
Neisseria Gonorrhoeae ◽  
False Negative ◽  
Public Health Problem ◽  
Surveillance Program ◽  
Major Public Health Problem ◽  
Negative Results ◽  
False Negative Results ◽  
Confirmatory Tests ◽  
Polymerase Chain ◽  
Low Prevalence

porA pseudogene-negative Neisseria gonorrhoeae isolates produce false-negative results when examined by polymerase chain reaction (PCR) with porA pseudogene targets. In the present study, 533 representative gonococcal isolates received in 2011 via the Gonococcal Resistance to Antimicrobials Surveillance Program were examined to determine the prevalence of porA-negative isolates. Less than 0.4% (2/533) of isolates were found to be reproducibly negative with the porA real-time PCR but were confirmed as N. gonorrhoeae with molecular, biochemical and immunological confirmatory tests. Sequencing revealed both isolates contained the Neisseria meningitidis porA gene. Low prevalence indicates that although these isolates do not present a major public health problem, microbiologists should remain vigilant.

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 Reducing False Negative PCR Test for COVID-19

2020 ◽  
Vol 9 (3) ◽  
pp. 408-410
Author(s):  
Fatemeh Bahreini ◽  
Rezvan Najafi ◽  
Razieh Amini ◽  
Salman Khazaei ◽  
Saeid Bashirian
Keyword(s):  
Polymerase Chain Reaction ◽  
Real Time ◽  
False Negative ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Creative Commons ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain ◽  
Pcr Test

As the SARS-CoV-2 (COVID-19) pandemic spreads rapidly, there is need for a diagnostic test with high accuracy to detect infected individuals especially those without symptoms. Real-time polymerase chain reaction (RT-PCR) is a common molecular test for diagnosing SARS-CoV-2. If some factors are not taken into consideration when performing this test, it can have a relatively large number of false negative results. In this article, we discuss important considerations that could lead to false negative test reduction. Key words: • SARS-CoV-2 • COVID-19 • Real time polymerase chain reaction • RT-PCR test • Diagnosis • False negatives • Genetics • Emerging disease   Copyright © 2020 Bahreini et al. Published by Global Health and Education Projects, Inc. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0)which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in this journal, is properly cited.

scholarly journals False-Negative Nasopharyngeal Swab RT-PCR Assays in Typical COVID-19: Role of Ultra-low-dose Chest CT and Bronchoscopy in Diagnosis

2020 ◽  
Author(s):  
Marco Marando ◽  
Adriana Tamburello ◽  
Pietro Gianella
Keyword(s):  
Low Dose ◽  
False Negative ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Oral Swab ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain ◽  
Pcr Assays

On 11 March 2020, the WHO declared COVID-19 a pandemic and global health emergency. We describe the clinical features and role of ultra-low-dose chest computed tomography (CT) and bronchoscopy in the diagnosis of coronavirus disease (COVID-19). In our patient, who was highly suggestive clinically and radiologically for COVID-19, we had two false-negative results for nasopharyngeal and oral swab reverse-transcriptase polymerase chain reaction (RT-PCR) assays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Eventually, we confirmed the diagnosis using bronchoscopy and bronchoalveolar lavage (BAL).

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.

scholarly journals The frequency and character of community-acquired pneumonia comparison before and during the COVID-19 epidemic in the multi-specialty hospital

2020 ◽  
Vol 1 (1) ◽  
pp. 37-47
Author(s):  
Stepan A. Yaremenko ◽  
Natalia A. Rucheva ◽  
Kirill N. Zhuravlev ◽  
Valentin E. Sinitsyn
Keyword(s):  
Retrospective Analysis ◽  
False Negative ◽  
Community Acquired Pneumonia ◽  
Chest Ct ◽  
Viral Pneumonia ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain ◽  
Ct Data ◽  
Suspected Pneumonia

BACKGROUND:The 2019 coronavirus disease outbreak (COVID-19) quickly swept the world in just a month. Polymerase chain reaction (PCR) is used in the diagnosis of this disease, but this test has limitations related to false negative results, as well as PCR is a time-consuming procedure. Under these conditions, chest computed tomography (CT) can become one of the main methods in the Clinicians Arsenal used for early detection of COVID-19 in patients who first seek medical help. AIMS:comparison of the frequency of community-acquired pneumonia and its characteristics according to CT data before and during the COVID-19 epidemic and study of the possibilities of their timely detection and differential diagnosis. MATERIALS AND METHODS:A retrospective analysis of chest CT scans results was performed in Davydovsky hospital (Moscow) from April 1 to April 17, 2020. It included all patients diagnosed with viral pneumonia at the CT. All patients with suspected diagnosis of viral pneumonia underwent PCR testing. Retrospective analysis of chest CT data from patients admitted to the hospital with suspected pneumonia for the same period in 2019 was taken as a comparison group. RESULTS:For the period from April 1 to April 17, 2020 according to chest CT, pneumonia was diagnosed in 140 cases, of which 65 (46.4%) were described as viral, compared with the same period in 2019 7 diagnoses of viral pneumonia (10.3%) were described a significant increase in cases of viral pneumonia (5.723;p0.01). Results of PCR test in patients with viral pneumonia according to CT data was: positive in 34 (52.3%), negative in 22 (33.8%), 9 (13.9%) patients were not tested. When comparing the frequency of detection on CT of viral pneumonia patterns in patients for the same period of time in 2019 and 2020, no significant differences were found. The probability of COVID-19 due to results of chest CT was: average 13.8%, high 75.4%. The severity of viral pneumonia according to CT data was: light 38.5%, medium 46.2%, severe 12.3%, extremely severe 3.1%. CONCLUSIONS:Rapid CT diagnostics of COVID-19, even with false negative results of PCR tests, can help to isolate a patient with suspected COVID-19, start treatment on time and prevent the further spread of viral infection in a pandemic. Nevertheless, due to the non-specificity of the revealed picture, the possibilities of CT to identify lung lesions by specific viral agents are limited.

Development of a Polymerase Chain Reaction Assay for Detection of Burkholderia mallei, a Potent Biological Warfare Agent

2016 ◽  
Vol 66 (5) ◽  
pp. 458 ◽  
Author(s):  
Vijai Pal ◽  
Sandeep Singh ◽  
Arvind Kumar Tiwari ◽  
Y.K. Jaiswal ◽  
G.P. Rai
Keyword(s):  
Polymerase Chain Reaction ◽  
Tap Water ◽  
False Negative ◽  
Burkholderia Mallei ◽  
Chain Reaction ◽  
Pcr Assay ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain ◽  
Rapid Tool

Burkholderia mallei is the etiological agent of glanders, primarily a disease of equines. B. mallei is closely related to B. pseudomallei, the causative agent of melioidosis. Therefore, detection of B. mallei and its differentiation from B. pseudomallei, has always been troublesome. In present investigation, a B. mallei specific DNA sequence was identified by performing BLASTn search using ~3000 ORFs of B. mallei NCTC 10229. A polymerase chain reaction (PCR) assay with internal amplification control (IAC) was developed for detection of B. mallei and its differentiation from B. pseudomallei. The PCR assay could amplify a specific 224-bp fragment from all the six B. mallei strains used in the study, whereas other closely related organisms were tested negative. The detection limit of the assay was found to be 10 pg of purified DNA of B. mallei. Incorporation of IAC in the assay makes the results reliable as false negative results which may arise due to presence of PCR inhibitors, can be avoided. For validation, the assay was tested on tap water, Bengal gram and grass artificially spiked with B. mallei. The developed assay can be used as a simple and rapid tool for detection of B. mallei.

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