Molecular diagnostic technologies for COVID-19: Limitations and challenges

On the Challenges for the Diagnosis of SARS-CoV-2 Based on a Review of Current Methodologies

Diagnosis of COVID-19 has been challenging owing to the need for mass testing and for combining distinct types of detection to cover the different stages of the infection. In this review, we have surveyed the most used methodologies for diagnosis of COVID-19, which can be basically categorized into genetic-material detection and immunoassays. Detection of genetic material with real-time polymerase chain reaction (RT-PCR) and similar techniques has been achieved with high accuracy, but these methods are expensive and require time-consuming protocols which are not widely available, especially in less developed countries. Immunoassays for detecting a few antibodies, on the other hand, have been used for rapid, less expensive tests, but their accuracy in diagnosing infected individuals has been limited. We have therefore discussed the strengths and limitations of all of these methodologies, particularly in light of the required combination of tests owing to the long incubation periods. We identified the bottlenecks that prevented mass testing in many countries, and proposed strategies for further action, which are mostly associated with materials science and chemistry. Of special relevance are the methodologies which can be integrated into point-of-care (POC) devices and the use of artificial intelligence that do not require products from a well-developed biotech industry.

August 2020 Interim EuGMS guidance to prepare European Long-Term Care Facilities for COVID-19

PURPOSE

The European Geriatric Medicine Society (EuGMS) is launching a second interim guidance whose aim is to prevent the entrance and spread of COVID-19 into long-term care facilities (LTCFs).

METHODS

The EuGMS gathered experts to propose a guide of measures to prevent COVID-19 outbreaks in LTCFs. It is based on the specific features of SARS-CoV-2 transmission in LTCFs, residents' needs, and on experiences conducted in the field.

RESULTS

Asymptomatic COVID-19 residents and staff members contribute substantially to the dissemination of COVID-19 infection in LTCFs. An infection prevention and control focal point should be set up in every LTCF for (1) supervising infection prevention and control measures aimed at keeping COVID-19 out of LTCFs, (2) RT-PCR testing of residents, staff members, and visitors with COVID-19 symptoms, even atypical, and (3) isolating subjects either infected or in contact with infected subjects. When a first LCTF resident or staff member is infected, a facility-wide RT-PCR test-retest strategy should be implemented for detecting all SARS-CoV-2 carriers. Testing should continue until no new COVID-19 cases are identified. The isolation of residents should be limited as much as possible and associated with measures aiming at limiting its negative effects on their mental and somatic health status.

CONCLUSIONS

An early recognition of symptoms compatible with COVID-19 may help to diagnose COVID-19 residents and staff more promptly. Subsequently, an earlier testing for SARS-CoV-2 symptomatic and asymptomatic LTCF staff and residents will enable the implementation of appropriate infection prevention and control. The negative effects of social isolation in residents should be limited as much as possible.

An Update on Molecular Diagnostics for COVID-19

A novel strain of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) disease (COVID-19) has been recently identified as an infectious disease affecting the respiratory system of humans. This disease is caused by SARS-CoV-2 that was identified in Chinese patients having severe pneumonia and flu-like symptoms. COVID-19 is a contagious disease that spreads rapidly via droplet particles arising through sneezing and coughing action of an infected person. The reports of asymptomatic carriers changed the scenario of symptom based-diagnosis in COVID-19 and intensified the need for proper diagnosis of the majority of the population to combat the rapid transmission of virus. The diagnosis of positive cases is necessary to ensure prompt care to affected people and also to curb further spread of infection in the population. Collecting samples at the right time and from the exact anatomical site is crucial for proper molecular diagnosis. After the complete genome sequence was available, China formulated RT-PCR as a primary diagnostic procedure for detecting SARS-CoV-2. Many in-house and commercial diagnostic kits have been developed or are under development that have a potential to lower the burden of diagnosis on the primary diagnostic techniques like RT-PCR. Serological based diagnosis is another broad category of testing that can detect different serum antibodies like IgG, IgM, and IgA in an infected patient. PCR-based diagnostic procedures that are commonly used for pathogen detection need sophisticated machines and assistance of a technical expert. Despite their reliable accuracy, they are not cost-effective tests, which a common man can afford, so it becomes imperative to look for other diagnostic approaches, which could be cost effective, rapid, and sensitive with consistent accuracy. To make such diagnostics available to the common man, many techniques can be exploited among, which are Point of Care (POC), also known as bed side testing, which is developing as a portable and promising tool in pathogen diagnosis. Other lateral flow assay (LFA)-based techniques like SHERLOCK, CRISPR-Cas12a (AIOD-CRISPR), and FNCAS9 editor-limited uniform detection assay (FELUDA), etc. have shown promising results in rapid detection of pathogens. Diagnosis holds a critical importance in the pandemic situation when there is no potential drug for the pathogen available in the market. This review sums up the different diagnostic approaches designed or proposed to combat the crisis of widespread diagnosis due to the sudden outbreak of a novel pathogen, SARS-CoV-2 in 2019.

Printed Electrochemical Biosensors: Opportunities and Metrological Challenges

Printed electrochemical biosensors have recently gained increasing relevance in fields ranging from basic research to home-based point-of-care. Thus, they represent a unique opportunity to enable low-cost, fast, non-invasive and/or continuous monitoring of cells and biomolecules, exploiting their electrical properties. Printing technologies represent powerful tools to combine simpler and more customizable fabrication of biosensors with high resolution, miniaturization and integration with more complex microfluidic and electronics systems. The metrological aspects of those biosensors, such as sensitivity, repeatability and stability, represent very challenging aspects that are required for the assessment of the sensor itself. This review provides an overview of the opportunities of printed electrochemical biosensors in terms of transducing principles, metrological characteristics and the enlargement of the application field. A critical discussion on metrological challenges is then provided, deepening our understanding of the most promising trends in order to overcome them: printed nanostructures to improve the limit of detection, sensitivity and repeatability; printing strategies to improve organic biosensor integration in biological environments; emerging printing methods for non-conventional substrates; microfluidic dispensing to improve repeatability. Finally, an up-to-date analysis of the most recent examples of printed electrochemical biosensors for the main classes of target analytes (live cells, nucleic acids, proteins, metabolites and electrolytes) is reported.

Recurrence of SARS-CoV-2 viral RNA in recovered COVID-19 patients: a narrative review

Many studies have shown that re-positive tests for SARS-CoV-2 by RT-PCR in recovered COVID-19 patients are very common. We aim to conduct this review to summarize the clinical and epidemiological characteristics of these patients and discuss the potential explanations for recurrences, the contagiousness of re-detectable positive SARS-CoV-2 virus, and the management of COVID-19 patients after discharge from hospital. The proportion of re-positive tests in discharged COVID-19 patients varied from 2.4 to 69.2% and persisted from 1 to 38 days after discharge, depending on population size, age of patients, and type of specimens. Currently, several causes of re-positive tests for SARS-CoV-2 in recovered COVID-19 patients are suggested, including false-negative, false-positive RT-PCR tests; reactivation; and re-infection with SARS-CoV-2, but the mechanism leading to these re-positive cases is still unclear. The prevention of re-positive testing in discharged patients is a fundamental measure to control the spread of the pandemic. In order to reduce the percentage of false-negative tests prior to discharge, we recommend performing more than two tests, according to the standard sampling and microbiological assay protocol. In addition, specimens should be collected from multiple body parts if possible, to identify SARS-CoV-2 viral RNA before discharge. Further studies should be conducted to develop novel assays that target a crucial region of the RNA genome in order to improve its sensitivity and specificity.

Trends in MERS-CoV, SARS-CoV, and SARS-CoV-2 (COVID-19) Diagnosis Strategies: A Patent Review

The emergence of a new coronavirus (SARS-CoV-2) outbreak represents a challenge for the diagnostic laboratories responsible for developing test kits to identify those infected with SARS-CoV-2. Methods with rapid and accurate detection are essential to control the sources of infection, to prevent the spread of the disease and to assist decision-making by public health managers. Currently, there is a wide variety of tests available with different detection methodologies, levels of specificity and sensitivity, detection time, and with an extensive range of prices. This review therefore aimed to conduct a patent search in relation to tests for the detection of SARS-CoV, MERS-CoV, and SARS-CoV-2. The greatest number of patents identified in the search were registered between 2003 and 2011, being mainly deposited by China, the Republic of Korea, and the United States. Most of the patents used the existing RT-PCR, ELISA, and isothermal amplification methods to develop simple, sensitive, precise, easy to use, low-cost tests that reduced false-negative or false-positive results. The findings of this patent search show that an increasing number of materials and diagnostic tests for the coronavirus are being produced to identify infected individuals and combat the growth of the current pandemic; however, there is still a question in relation to the reliability of the results of these tests.

Paper-based devices for rapid diagnostics and testing sewage for early warning of COVID-19 outbreak

Coronavirus disease (COVID-19), caused by SARS-CoV-2, evolved into a global pandemic in 2020, and the outbreak has taken an enormous toll on individuals, families, communities and societies around the world. One practical and effective strategy is to implement rapid case identification based on a rapid testing to respond to this public health crisis. Currently, the available technologies used for rapid diagnostics include RT-PCR, RT-LAMP, ELISA and NGS. Still, due to their different limitations, they are not well suited for rapid diagnosis in a variety of locations. Paper-based devices are alternative approaches to achieve rapid diagnosis, which are cost-effective, highly selective, sensitive, portable, and easy-to-use. In addition to individual virus screening, wastewater-based epidemiology has been emerged to be an effective way for early warning of outbreak within the population, which tests viral genome sequence to reflect information on the spread and distribution of the virus because SARS-CoV-2 can be shed into wastewater through the feces and urine from infected population. In this paper, we describe paper-based device as a low-cost and rapid sensor for both diagnosis and testing of sewage for early warning of outbreak. More importantly, the device has great potential for real-time detection in the field, without any advanced facilities or well-trained and skilled personnel, and provides early warning or timely intervention of an outbreak of pandemic.