Detection of <em>Mycobacterium leprae</em> using real-time PCR in paucibacillary leprosy patients with negative acid-fast bacilli smears

BACKGROUND Leprosy is an infectious disease that is still a health problem worldwide, including in Indonesia. The clinical symptoms are similar to other skin diseases and it is difficult to establish a diagnosis for paucibacillary (PB) leprosy. Current serological and histopathological tests have limitations, especially in patients with negative acid-fast bacilli (AFB). Serological tests often give false-negative results, while histopathological results often consist of non-specific inflammation. Probe-based real-time polymerase chain reaction (RT-PCR) assays is an alternative test that may be more sensitive and more specific to detect Mycobacterium leprae. METHODS This study was done in June 2015 until March 2016; detected M. leprae in PB patients with negative AFB smears using TaqMan® probe-based RT-PCR assay on slit skin scrapings and skin biopsy specimens from 24 patients. The skin scrapings were obtained from skin tissue on ear lobes, skin lesions, as well as those from biopsy. Samples were tested with RT-PCR while histopathological examinations were only performed on skin from biopsy. RESULTS The RT-PCR assay showed positive results of 21%, 25%, and 96% for specimens obtained from skin scrapings of the ear lobe, skin lesions, and skin biopsy, respectively. On the other hand, the positive rate for the histopathological test from skin biopsy was 79%. It indicated that the TaqMan® RT-PCR assay could increase the diagnostic capacity of histopathological examination by as much as 17%. CONCLUSIONS TaqMan® PCR assay can improve the diagnostic capacity of histopathological examinations, which could be used as the new gold standard for the diagnosis of leprosy.

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Rapid SARS-CoV-2 antigen detection assay in comparison with real-time RT-PCR assay for laboratory diagnosis of COVID-19 in Thailand

Virology Journal ◽

10.1186/s12985-020-01452-5 ◽

2020 ◽

Vol 17 (1) ◽

Cited By ~ 3

Author(s):

Chutikarn Chaimayo ◽

Bualan Kaewnaphan ◽

Nattaya Tanlieng ◽

Niracha Athipanyasilp ◽

Rujipas Sirijatuphat ◽

...

Keyword(s):

Real Time ◽

Sensitivity And Specificity ◽

False Negative ◽

Laboratory Diagnosis ◽

Antigen Detection ◽

Rt Pcr ◽

Pcr Assay ◽

Screening Assay ◽

The Real ◽

Pcr Test

Abstract Background The Coronavirus disease 2019 (COVID-19) pandemic continues to spread across the world. Hence, there is an urgent need for rapid, simple, and accurate tests to diagnose severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Performance characteristics of the rapid SARS-CoV-2 antigen detection test should be evaluated and compared with the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) test for diagnosis of COVID-19 cases. Methods The rapid SARS-CoV-2 antigen detection test, Standard™ Q COVID-19 Ag kit (SD Biosensor®, Republic of Korea), was compared with the real-time RT-PCR test, Allplex™ 2019-nCoV Assay (Seegene®, Korea) for detection of SARS-CoV-2 in respiratory specimens. Four hundred fifty-four respiratory samples (mainly nasopharyngeal and throat swabs) were obtained from COVID-19 suspected cases and contact individuals, including pre-operative patients at Siriraj Hospital, Bangkok, Thailand during March–May 2020. Results Of 454 respiratory samples, 60 (13.2%) were positive, and 394 (86.8%) were negative for SARS-CoV-2 RNA by real-time RT-PCR assay. The duration from onset to laboratory test in COVID-19 suspected cases and contact individuals ranged from 0 to 14 days with a median of 3 days. The rapid SARS-CoV-2 antigen detection test’s sensitivity and specificity were 98.33% (95% CI, 91.06–99.96%) and 98.73% (95% CI, 97.06–99.59%), respectively. One false negative test result was from a sample with a high real-time RT-PCR cycle threshold (Ct), while five false positive test results were from specimens of pre-operative patients. Conclusions The rapid assay for SARS-CoV-2 antigen detection showed comparable sensitivity and specificity with the real-time RT-PCR assay. Thus, there is a potential use of this rapid and simple SARS-CoV-2 antigen detection test as a screening assay.

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Multi-site Evaluation of SARS-CoV-2 Spike Mutation Detection Using a Multiplex Real-time RT-PCR Assay

10.1101/2021.05.05.21254713 ◽

2021 ◽

Author(s):

Carolin Bier ◽

Anke Edelmann ◽

Kathrin Theil ◽

Rolf Schwarzer ◽

Maria Deichner ◽

...

Keyword(s):

Real Time ◽

Limit Of Detection ◽

False Negative ◽

Analytical Sensitivity ◽

Test Results ◽

Rt Pcr ◽

Pcr Assay ◽

Clinical Specimens ◽

Negative Results ◽

Global Pandemic

Background. SARS-CoV-2 causes COVID-19, which can be fatal and is responsible for a global pandemic. Variants with increased transmissibility or the potential to evade immunity have emerged and represent a threat to global pandemic control. Variants of concern (VOC) can be identified by sequencing of viral RNA, or by more rapid methods for detection of subsets of signature mutations. Methods. We developed a multiplex, real-time RT-PCR assay (cobas SARS-CoV-2 Variant Set 1) for the qualitative detection and differentiation of three key SARS-CoV-2 mutations in the viral spike protein: del 69-70, E484K and N501Y. Analytical sensitivity and accuracy were evaluated at three testing sites using clinical specimens from patients infected with SARS-CoV-2 variants belonging to several different lineages, including B.1.1.7, B.1.351, and P.1. Results. The limit of detection for E484K was between 180 and 620 IU/mL for the three different isolates tested. For N501Y, the LOD was between 270 and 720 IU/mL (five isolates), while for del 69-70, it was 80 - 92 IU/mL (two isolates). Valid test results were obtained with all clinical specimens that were positive using routine diagnostic tests. Compared to sequencing (Sanger and next-generation), test results were 100% concordant at all three loci; no false positive or false negative results were observed. Conclusions. Data collected at three independent laboratories indicates excellent performance and concordance of cobas SARS-CoV-2 Variant Set 1 with sequencing. New sets of primers and probes that target additional loci can be rapidly deployed in response to the identification of other emerging variants.

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Analysis of external quality assessment samples revealed crucial performance differences between commercial RT-PCR assays for SARS-CoV-2 detection when taking extraction methods and real-time-PCR instruments into account

10.1101/2020.09.18.20185744 ◽

2020 ◽

Author(s):

Monika Malecki ◽

Jessica Luesebrink ◽

Andreas Wendel ◽

Frauke Mattner

Keyword(s):

Real Time ◽

External Quality Assessment ◽

False Negative ◽

Clinical Results ◽

Extraction Methods ◽

Contact Tracing ◽

Clinical Settings ◽

Rt Pcr ◽

Pcr Assay ◽

Wide Range

In limelight of the ongoing pandemic SARS-CoV-2 testing is critical for the diagnosis of infected patients, contact-tracing and mitigating the transmission. Diagnostic laboratories are expected to provide appropriate testing with maximum accuracy. Real-time reverse transcriptase PCR (RT-PCR) is the diagnostic standard yet many commercial diagnostic kits have become available. However, only a handful of studies have reviewed their performance in clinical settings. The aim of this study was to compare the performance of the overall analytical matrix including the extraction kit (BD MAX, Promega, Qiagen), the PCR instrument (Agilent Mx3005P, BD MAX, Qiagen Rotor-Gene, Roche Cobas z 480) and the RT-PCR assay (Altona Diagnostics, CerTest Biotec, R-Biopharm AG) using predefined samples from proficiency testing organizers. The greatest difference of the Ct values between the matrices was 9 cycles. One borderline sample could not be detected by 3 out of 12 analytical matrices and yielded a false negative result. We therefore conclude that diagnostic laboratories should take the complete analytical matrix in addition to the performance values published by the manufacturer for a respective RT-PCR kit into account. With limited resources laboratories have to validate a wide range of kits to determine appropriate analytical matrices for detecting SARS-CoV-2 reliably. The interpretation of clinical results has to be adapted accordingly.

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Scoring System for the Diagnosis of COVID-19

The Open Public Health Journal ◽

10.2174/1874944502013010413 ◽

2020 ◽

Vol 13 (1) ◽

pp. 413-414 ◽

Cited By ~ 1

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.

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A misleading false-negative result of Pneumocystis real-time PCR assay due to a rare punctual mutation: A French multicenter study

Medical Mycology ◽

10.1093/mmy/myw051 ◽

2016 ◽

Vol 55 (2) ◽

pp. 180-184 ◽

Cited By ~ 11

Author(s):

Solène Le Gal ◽

Florence Robert-Gangneux ◽

Yann Pépino ◽

Sorya Belaz ◽

Céline Damiani ◽

...

Keyword(s):

Real Time ◽

Multicenter Study ◽

Real Time Pcr ◽

False Negative ◽

False Negative Result ◽

Pcr Assay

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Viral Dynamics and Real-Time RT-PCR Ct Values Correlation with Disease Severity in COVID-19

Diagnostics ◽

10.3390/diagnostics11061091 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1091

Author(s):

Ali A. Rabaan ◽

Raghavendra Tirupathi ◽

Anupam A Sule ◽

Jehad Aldali ◽

Abbas Al Mutair ◽

...

Keyword(s):

Viral Load ◽

Real Time ◽

Disease Severity ◽

False Negative ◽

Influential Factors ◽

Confirmatory Test ◽

Acid Extraction ◽

Rt Pcr ◽

Viral Kinetics ◽

Ct Value

Real-time RT-PCR is considered the gold standard confirmatory test for coronavirus disease 2019 (COVID-19). However, many scientists disagree, and it is essential to understand that several factors and variables can cause a false-negative test. In this context, cycle threshold (Ct) values are being utilized to diagnose or predict SARS-CoV-2 infection. This practice has a significant clinical utility as Ct values can be correlated with the viral load. In addition, Ct values have a strong correlation with multiple haematological and biochemical markers. However, it is essential to consider that Ct values might be affected by pre-analytic, analytic, and post-analytical variables such as collection technique, specimen type, sampling time, viral kinetics, transport and storage conditions, nucleic acid extraction, viral RNA load, primer designing, real-time PCR efficiency, and Ct value determination method. Therefore, understanding the interpretation of Ct values and other influential factors could play a crucial role in interpreting viral load and disease severity. In several clinical studies consisting of small or large sample sizes, several discrepancies exist regarding a significant positive correlation between the Ct value and disease severity in COVID-19. In this context, a revised review of the literature has been conducted to fill the knowledge gaps regarding the correlations between Ct values and severity/fatality rates of patients with COVID-19. Various databases such as PubMed, Science Direct, Medline, Scopus, and Google Scholar were searched up to April 2021 by using keywords including “RT-PCR or viral load”, “SARS-CoV-2 and RT-PCR”, “Ct value and viral load”, “Ct value or COVID-19”. Research articles were extracted and selected independently by the authors and included in the present review based on their relevance to the study. The current narrative review explores the correlation of Ct values with mortality, disease progression, severity, and infectivity. We also discuss the factors that can affect these values, such as collection technique, type of swab, sampling method, etc.

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Development and application of a real-time RT-PCR assay to rapidly detect H2 subtype avian influenza A viruses

Journal of Veterinary Diagnostic Investigation ◽

10.1177/1040638721994810 ◽

2021 ◽

pp. 104063872199481

Author(s):

Yixin Xiao ◽

Fan Yang ◽

Fumin Liu ◽

Hangping Yao ◽

Nanping Wu ◽

...

Keyword(s):

Avian Influenza ◽

Real Time ◽

Influenza A ◽

Minor Groove Binder ◽

Rt Pcr ◽

Influenza A Viruses ◽

Pcr Assay ◽

Infectious Dose ◽

The Matrix ◽

Taqman Minor Groove Binder

The H2 subtypes of avian influenza A viruses (avian IAVs) have been circulating in poultry, and they have the potential to infect humans. Therefore, establishing a method to quickly detect this subtype is pivotal. We developed a TaqMan minor groove binder real-time RT-PCR assay that involved probes and primers based on conserved sequences of the matrix and hemagglutinin genes. The detection limit of this assay was as low as one 50% egg infectious dose (EID50)/mL per reaction. This assay is specific, sensitive, and rapid for detecting avian IAV H2 subtypes.

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Pooling of Upper Respiratory Specimens Using a SARS-CoV-2 Real-time RT-PCR Assay Authorized for Emergency Use in Low-Prevalence Populations for High-Throughput Testing

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa466 ◽

2020 ◽

Vol 7 (11) ◽

Author(s):

Gwynngelle A Borillo ◽

Ron M Kagan ◽

Russell E Baumann ◽

Boris M Fainstein ◽

Lamela Umaru ◽

...

Keyword(s):

Real Time ◽

False Negative ◽

False Negative Rate ◽

Nucleic Acid Amplification ◽

Rt Pcr ◽

Pooled Testing ◽

Negative Results ◽

Single Positive ◽

Upper Respiratory ◽

Respiratory Specimens

Abstract Background Nucleic acid amplification testing is a critical tool for addressing the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Specimen pooling can increase throughput and conserve testing resources but requires validation to ensure that reduced sensitivity does not increase the false-negative rate. We evaluated the performance of a real-time reverse transcription polymerase chain reaction (RT-PCR) test authorized by the US Food and Drug Administration (FDA) for emergency use for pooled testing of upper respiratory specimens. Methods Positive specimens were selected from 3 prevalence groups, 1%–3%, >3%–6%, and >6%–10%. Positive percent agreement (PPA) was assessed by pooling single-positive specimens with 3 negative specimens; performance was assessed using Passing-Bablok regression. Additionally, we assessed the distributions of RT-PCR cycle threshold (Ct) values for 3091 positive specimens. Results PPA was 100% for the 101 pooled specimens. There was a linear relationship between Ct values for pooled and single-tested specimens (r = 0.96–0.99; slope ≈ 1). The mean pooled Ct shifts at 40 cycles were 2.38 and 1.90, respectively, for the N1 and N3 targets. The median Cts for 3091 positive specimens were 25.9 (N1) and 24.7 (N3). The percentage of positive specimens with Cts between 40 and the shifted Ct was 1.42% (N1) and 0.0% (N3). Conclusions Pooled and individual testing of specimens positive for SARS-CoV-2 demonstrated 100% agreement, which demonstrates the viability of pooled specimens for SARS-COV-2 testing using a dual-target RT-PCR system. Pooled specimen testing can help increase testing capacity for SARS-CoV-2 with a low risk of false-negative results.

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