Figure 4 - uploaded by Ahmed E. Dhamad
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Schematic flowchart of indirect ELISA. A coated SARS-CoV-2 protein (antigen) onto wells of ELISA plate (A) interacts with the first antibody (anti-SARS-CoV-2 antibody) that is in a patient's sample (B). (C) After adding a secondary antibody (a conjugated antibody), it recognizes and interacts with the first antibodies. The reaction is developed by adding a substrate (D) which is cleaved by the conjugated enzyme and changes the reaction color after incubation (E) and (F), respectively. (G) Results are read by ELISA plate reader. The figure was created with BioRender. com. Full-size DOI: 10.7717/peerj.10180/fig-4
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Since COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was declared as a pandemic disease by the World Health Organization in early 2020, many countries, organizations and companies have tried to find the best way to diagnose the virus and contain its spreading. SARS-CoV-2 is a positive-sense single RNA (+ssRNA) cor...
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... color is detected and measured by a plate reader (Fig. 4). ELISA is relatively fast (2-5 h) and cheap compared to rRT-PCR, and it is similar to FLA regard to accuracy. It has been reported that ELISA results were 50% (IgG) and 81% (IgM) for patients on day zero and became 81% (IgG) and 100%(IgM) on day five of SARS-CoV-2 infection ( ). Another study accomplished by showed that using ELISA to ...
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... color is detected and measured by a plate reader (Fig. 4). ELISA is relatively fast (2-5 h) and cheap compared to rRT-PCR, and it is similar to FLA regard to accuracy. It has been reported that ELISA results were 50% (IgG) and 81% (IgM) for patients on day zero and became 81% (IgG) and 100%(IgM) on day five of SARS-CoV-2 infection ( ). Another study accomplished by showed that using ELISA to ...
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Background: The global outbreak of coronavirus disease 2019 (COVID-19) has been ongoing in Southeast Asia since 13 January 2020. We conducted an observational study to investigate underlying disease patterns of COVID-19 in Southeast Asia, and consequently to guide intervention strategies against the pandemic.
Methods: In this population-level obser...
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... Sonuç, test şeridinin hangi bölgesinin renklendiğine göre belirlenir. Alınan numunenin özelliğine (sıvının hızı, kılcal kuvveti, akışkanlığı, ) göre de sonuçlar etkilenmektedir 4,12,23,24 . Bu testler; uzman bir personele ihtiyaç duymadan kısa bir sürede sonuç verebilmektedir. ...
... Diğer test yöntemlerinden farklı olarak, geçmiş ve mevcut SARS-CoV-2 enfeksiyonunu hastanın serum, plazma vb vücut sıvılarında antikor (IgA, IgM, IgG) tespiti ile, hastalık dönemlerinin ilerlemesini ve bağışıklık tepkisini izlemek için kullanılmaktadır. Antikor testleri olarak da adlandırılabilir 23 . İmmünglobulinlerin tespiti ELİSA (Enzim Bağlantılı İmmünosorbent Testi) veya CLİA (Kemilüminesans İmmünolojik Testler) ile yapılabileceği gibi LFA (Yanal Akış Testleri) ile hızlı ve pratik olarak hasta başında da gerçekleştirilebilir 4,12 . ...
... Taramada kullanılmasının önündeki bir diğer dezavantaj ise diğer koronoviridea ailesi üyelerinin enfeksiyonları sonucu gelişen antikorlar ile çapraz reaksiyon nedeniyle yanlış sonuçlardır. Bunun dışında genel olarak da özgüllüğü ve duyarlılığı diğer test yöntemlerine göre düşüktür 23 . COVID-19 aşılarının ortaya konması ve yaygınlaşması ile daha çok aşıların etkililiğinin değerlendirilmesi için kullanılmaya başlanmıştır. ...
COVID-19 ile mücadelede; hastalıkla enfekte olmuş kişilerin tespiti ve sonrasında izole edilmesi son derece önemlidir. Bu amaçla dünya genelinde kullanılan tanı testleri, çeşitlilik ve uygulama kriterleri açısından farklılık göstermektedir. Bu derlemede halk sağlığı bakış açısıyla; COVID-19 tanısı için kullanılan testler ile kimlere yönelik ve nasıl kullanıldığının yanısıra test kullanımı konusundaki yaklaşımlar ele alınmıştır. Polimeraz zincir reaksiyonu (PCR) tabanlı testler, yüksek duyarlılık ve özgüllük değerleri dolayısıyla altın standart olarak kabul edilmektedir. Farklı örnek alma yöntemlerine yönelik karşılaştırmalar yapılmakla birlikte genel görüş, nazofaringeal sürüntü yönündedir. Altın standart tanı yöntemi olarak kabul edilmesine karşın bazı dezavantajları vardır. En önemlisi sonuçlanmasının uzun sürmesi ve yüksek maliyettir. Maliyeti azaltmak için birkaç örneğin tek bir örnek gibi değerlendirilmesi yani havuzlandırılması tercih edilebilir. Bu dezavantajlara alternatif olarak hızlı antijen testleri göz önünde bulundurulabilir. Hızlı antijen testlerinin pek çok farklı piyasa formu vardır. Bu testlerin özgüllükleri ve duyarlılıklarına yönelik pek çok çalışma yapılmakta olup farklı değerler bulunmaktadır. Genel olarak özgüllüklerinin yüksek ve duyarlılığının ise daha düşük olduğu tespit edilmiştir. Hastalığın semptomatik tanısının zorluğu, bazı kişilerin hastalığı bulaştırmasına karşın semptom göstermemesi sorunları için toplum taramaları çözüm yolu olabilir. Yeni varyantların ortaya çıkması ile dünya genelinde test politikalarında değişiklikler ve farklı yaklaşımlar gözlenmiştir. Daha geniş kapsamlı tarama yapmak amacıyla testlerin tüm halka açık hale getirilmesi veya toplum taramaları yönünde çalışmalar gerçekleştirilmiştir. Ancak artan PCR test yükü dolayısıyla bazı ülkelerde test yapılacak kişilerin kısıtlanması veya hızlı antijen testleri gibi alternatif test yöntemlerinin ek olarak kullanılması gibi test politikalarının uygulanması gerekmiştir.
... It is regarded as the gold standard for the diagnosis of SARS-CoV-2 due to its high sensitivity and high specificity [4,5], which is achieved by collecting samples from the upper respiratory tract (e.g., nasopharynx or oropharynx). However, this method is time-consuming and requires medical personnel with specialized skills, as well as a specific laboratory [6]. In addition, the RT-PCR method depends on the collected samples, and if the samples are not collected, transported, and stored appropriately, it could lead to false-negative results [7,8]. ...
The rapid spread of coronavirus disease 2019 (COVID-19) has posed enormous challenges to the global public health system. To deal with the COVID-19 pandemic crisis, the more accurate and convenient diagnosis of patients needs to be developed. This paper proposes a deep-learning-based COVID-19 detection method and evaluates its performance on embedded edge-computing devices. By adding an attention module and mixed loss into the original VGG19 model, the method can effectively reduce the parameters of the model and increase the classification accuracy. The improved model was first trained and tested on the PC X86 GPU platform using a large dataset (COVIDx CT-2A) and a medium dataset (integrated CT scan); the weight parameters of the model were reduced by around six times compared to the original model, but it still approximately achieved 98.80%and 97.84% accuracy, outperforming most existing methods. The trained model was subsequently transferred to embedded NVIDIA Jetson devices (TX2, Nano), where it achieved 97% accuracy at a 0.6−1 FPS inference speed using the NVIDIA TensorRT engine. The experimental results demonstrate that the proposed method is practicable and convenient; it can be used on a low-cost medical edge-computing terminal. The source code is available on GitHub for researchers.
... Among laboratories methods employed there is the serological profile, (e.g., ELISA -Enzyme-linked immunosorbent assay and RST -Rapid serology test), which it's used to analyze the presence of antibodies anti-SARS-CoV-2 proteins (antigens), even after the infection has passed. Furthermore, real-time RT-PCR is a molecular approach by viral RNA detection, increasing the accuracy of detection in the initial stages of infection (2,3). ...
O objetivo deste estudo retrospectivo, de centro único, é incluir todos os casos da primeira onda de casos de COVID-19 no Hospital Padre Germano Lauck, em Foz do Iguaçu - PR, Brasil, de abril a julho de 2020, confirmados por RT-PCR em tempo real e analisar as características epidemiológicas e clínicas. Descrevemos e analisamos, retrospectivamente, as características clínicas e epidemiológicas dos casos da primeira onda de COVID-19 na cidade de Foz do Iguaçu, no Brasil. Os dados categóricos são descritos por frequência e proporções, enquanto os dados numéricos são descritos pelo desvio padrão (DP) e pelo intervalo interquartil mediano (IQM). A idade média dos pacientes foi de 39 anos, incluindo 415 homens (44%) e 535 mulheres (56%). As comorbidades prevalentes foram diabetes, hipertensão e doença cardiovascular. Tosse, cefaleia e mialgia foram os sintomas comuns associados à COVID-19. A idade foi o principal fator de risco para a morte, assim como a hipertensão e o diabetes. Este estudo encontrou que a primeira onda de COVID-19 em Foz do Iguaçu apresentou características semelhantes aos estudos realizados durante o mesmo período epidemiológico. Quando comparadas com análises posteriores de diferentes cepas do vírus COVID-19, foi observado que houve uma predominância de diferentes sintomas e idades de casos graves entre as infecções causadas pelas variantes Ômicron e Delta.
... Moreover, shortening the time needed will aid in limiting both the economic and social impacts of pandemic outbreaks [29][30][31]. Among the available methods, the RT-rPCR represents a reliable approach to diagnosing SARS-CoV-2 with high sensitivity and specificity [32]. ...
Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly become a significant threat to public health. However, among the Coronaviridae family members, there are other viruses that can also cause infections in humans. Among these, severe acute respiratory syndrome (SARS-CoV) and Middle East respiratory syndrome (MERS-CoV) have posed significant threats to human health in the past. Other human pathogenic coronaviruses have been identified, and they are known to cause respiratory diseases with manifestations ranging from mild to severe. In this study, we evaluated the performance of a multiplex RT-rPCR specific to seven human pathogenic coronaviruses in mainly detecting SARS-CoV-2 directly from nasopharyngeal swabs obtained from suspected COVID-19 infected patients, while simultaneously detecting different human pathogenic coronaviruses in case these were also present. We tested 1195 clinical samples suspected of COVID-19 infection. The assay identified that 69% of the samples tested positive for SARS-CoV-2 (1195), which was confirmed using another SARS-CoV-2 RT-PCR kit available in our laboratory. None of these clinical samples were positive for SARS-CoV, MERS-CoV or HCoV. This means that during the endemic phase of COVID-19, infection with other human pathogenic coronaviruses, even the common cold coronavirus (HCoV), is very uncommon. Our study also confirmed that the multiplex RT-rPCR is a sensitive assay for detecting SARS-CoV-2 regardless of differences among the variants. This multiplex RT-rPCR is also time- and cost-saving and very easy to apply in the diagnostic laboratory due to its simple procedure and its stability in storage after preparation. These features make the assay a valuable approach in screening procedures for the rapid detection of SARS-CoV-2 and other human pathogenic coronaviruses that could affect public health.
... Serological methods are used to detect past and present SARS-CoV-2 infection. These methods can detect the presence of IgG, IgM and IgA antibodies in the serum and plasma of a covid-19 patient [26]. ...
Paper-based biosensors are highly preferred today as a self-operating microfluidic biosensor as a new generation biosensor due to its portability, low cost and simple fabrication. Biosensors known as paper based microfluidic analytical devices (μPAD), which have been used in a wide range of point-of-care analysis (Point-Of-Care-POC) applications in recent years, have begun to replace traditional diagnostic devices, especially in biomedical applications. Today, there are many different methods for the production of μPADs such as photolithography, inkjet printing, wax printing, paper cutting, plotting and plasma treatment. As an alternative to all these production methods, a new fabrication method has been developed for paper-based microfluidic devices created with toner using a laser printer. Washburn test was performed to examine the capillary flow performance of hydrophilic channels created on paper with the help of toner. In addition, the wettability of hy-drophobic barriers created with toner was determined by measuring the water contact angle. In order to test the success of the created system, the detection of a new type of coronavirus (SARS-CoV-2) has been tested on the system. Since the fabrication of the developed system is made with the toner used in laser printers, it is one of the lowest cost and most accessible methods performed until now, and it has a commercial product potential that can be used in the diagnosis of many diseases.
... Covid-19 patients are currently diagnosed using molecular and serological methods. Unlike molecular methods, serological methods have low accuracy in the early detection of patients with Covid-19 (Dhamad and Abdal Rhida, 2020). RT-qPCR is standard gold technique among all diagnostic methods. ...
Coronavirus disease 2019 (COVID19), caused by the severe acute respiratory syndrome coronavirus 2 (SARSCoV2), was first discovered in China in late 2019 and quickly spread worldwide. Although nasopharyngeal swab sampling is still the most popular approach identify SARS-CoV-2 carriers, other body samples may reveal the virus genome, indicating the potential for virus transmission via non-respiratory samples. In this study, researchers looked at the presence and degree of SARS-CoV-2 genome in stool and plasma samples from 191 Iranian COVID-19 patients, and looked for a link between these results and the severity of their disease. SARS-CoV-2 RNA shedding in feces and plasma of COVID-19 patients was assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Medical data were collected and evaluated, including Clinical features, demographics, radiological, and laboratory findings of the patients. Plasma samples from 117 confirmed laboratory patients were evaluated and 24 out of 117 patients (20.51%) tested positive for SARS-COV-2 RNA. Besides, 20 out of 74 patients (27.03%) tested positive for SARS-COV-2 RNA in stool samples. There seems to be no relationship between the presence of SARS-CoV-2 genome in fecal and plasma samples of Covid-19 patients and the severity of illness. We provide evidence of the SARS-CoV-2 genome presence in stool and plasma samples of Iranian COVID-19 patients.
... The enzyme-linked immunosorbent assay (ELISA) is widely used to identify a variety of viruses, such as novel coronaviruses (45). The various phases of the novel SARS-CoV-2 ELISA experiment are represented in Fig. 3 (46). The degree of sensitivity of this examination to IgG or IgM in COVID-19 positive patients is almost 84.3 percent (47). ...
The epidemic of COVID-19 spread quickly through China and engulfed all of the countries across the globe. Several advances have been made in understanding the novel coronavirus’s pathophysiology and in the development of newer diagnostics with pinpoint accuracy. Several newer therapeutic methods have either been accepted or are awaiting acceptance. In many countries, vaccination programs have been rolled out. Despite all these efforts, coronavirus still exists, though with lesser propensity. Multiple new forms of the novel coronavirus unexpectedly appeared in various areas of the world, undermining previously existing diagnosis and care protocols. This article highlights our understanding of the novel coronavirus’s symptoms in brief, pathogenesis, diagnostics, and therapeutic strategies to contain COVID-19. The clinical findings, including serological, radiological, and other advanced diagnostic strategies, contributed much to control the disease. To date, supportive interventions have been used in tandem with potent antiviral therapies such as remdesivir, lopinavir/ritonavir, or corticosteroids with a level of trust in the care of COVID-19 patients. However, in several areas of the world, vaccination initiatives took place; the vaccines’ safety and efficacy to control the outbreak is yet to be identified. This review concludes that improvement in therapies and diagnostics for COVID-19 must continually be explored as new variants constantly emerge.
... A serological test identifies an individual's antibody immune response against a specific past or current infection. The test detects the immune response through antibodies (such as Immunoglobulins IgG, IgM and IgA) in a COVID-19 patient's serum and plasma [81]. As such, the test is also unable to detect the early stage of infection. ...
SARS-CoV-2 presence in wastewater has been reported in several studies and has received widespread attention among the Wastewater-based epidemiology (WBE) community. Such studies can potentially be used as a proxy for early warning of potential COVID-19 outbreak, or as a mitigation measure for potential virus transmission via contaminated water. In this review, we summarized the latest understanding on the detection, concentration, and evaluation of SARS-CoV-2 in wastewater. Importantly, we discuss factors affecting the quality of wastewater surveillance ranging from temperature, pH, starting concentration, as well as the presence of chemical pollutants. These factors greatly affect the reliability and comparability of studies reported by various communities across the world. Overall, this review provides a broadly encompassing guidance for epidemiological study using wastewater surveillance.
... Typical laboratory-based serological analyses are performed by enzyme-linked immunosorbent assay, immunofluorescent assay, and chemiluminescence immunometric methods [5,6]. The analytical performances achieved by serological laboratory tests are, generally, performant in terms of sensitivity and specificity [7]. Many serological rapid tests have been also validated and put on the market, exploiting the lateral flow immunoassay (LFIA) format. ...
Lateral flow immunoassay (LFIA) is widely employed as point-of-care tests (POCT) for the diagnosis of infectious diseases. The accuracy of LFIA largely depends on the quality of the immunoreagents used. Typical LFIAs to reveal the immune response to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) employ anti-human immunoglobulin (hIG) antibodies and recombinant viral antigens, which usually are unstable and poorly soluble. Broad selective bacterial proteins, such as Staphylococcal protein A (SpA) and Streptococcal protein G (SpG) can be considered alternatives to anti-hIG to increase versatility and sensitivity of serological LFIAs because of their high binding capacity, interspecies reactivity, and robustness. We developed two colorimetric LFA devices including SpA and SpG linked to gold nanoparticles (GNP) as detectors and explored the use of a specific, stable, and soluble immunodominant fraction of the nucleocapsid protein from SARS-CoV-2 as the capturing agent. The optimal amount of SpA-GNP and SpG-GNP conjugates and the protein-to-GNP ratios were defined through a full factorial experimental design to maximize the diagnostic sensitivity of the LFIAs. The new LFA devices were applied to analyze 105 human serum samples (69 positive and 36 negatives according to reference molecular diagnostic methods). The results showed higher sensitivity (89.9%, 95% CI 82.7–97.0) and selectivity (91.7%, 82.6–100) for the SpA-based compared to the SpG-based LFA. In addition, 18 serum samples from cats and dogs living with COVID-19 patients were analyzed and 14 showed detectable levels of anti-SARS-CoV-2 antibodies, thus illustrating the flexibility of the SpA- and SpG-based LFAs.
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... Quantitative real-time PCR (qPCR) [37], next-generation sequencing (NGS) [38,39], enzyme-linked immunosorbent assays (ELISA) [40] are currently the most widely used "gold standard" methods, which are applied for the detection and identification of viral DNA in clinical practice [41][42][43]. Therefore, during the recent epidemic of COVID-19 [44,45], it is especially relevant to develop a new method or to adapt/optimize other specific, sensitive, rapid, inexpensive, accurate, already applicable techniques for early detection of a nucleic acid of interest in specific and environmentally friendly methods. ...
Early detection of viral pathogens by DNA-sensors in clinical samples, contaminated foods, soil or water can dramatically improve clinical outcomes and reduce the socioeconomic impact of diseases such as COVID-19. Clustered regularly interspaced short palindromic repeat (CRISPR) and its associated protein Cas12a (previously known as CRISPR-Cpf1) technology is an innovative new-generation genomic engineering tool, also known as ‘genetic scissors’, that has demonstrated the accuracy and has recently been effectively applied as appropriate (E-CRISPR) DNA-sensor to detect the nucleic acid of interest. The CRISPR-Cas12a from Prevotella and Francisella 1 are guided by a short CRISPR RNA (gRNA). The unique simultaneous cis- and trans- DNA cleavage after target sequence recognition at the PAM site, sticky-end (5–7 bp) employment, and ssDNA/dsDNA hybrid cleavage strategies to manipulate the attractive nature of CRISPR–Cas12a are reviewed. DNA-sensors based on the CRISPR-Cas12a technology for rapid, robust, sensitive, inexpensive, and selective detection of virus DNA without additional sample purification, amplification, fluorescent-agent- and/or quencher-labeling are relevant and becoming increasingly important in industrial and medical applications. In addition, CRISPR-Cas12a system shows great potential in the field of E-CRISPR-based bioassay research technologies. Therefore, we are highlighting insights in this research direction.
Graphical Abstract
