Recent Developments in SARS-CoV-2 Neutralizing Antibody Detection Methods.

The ongoing Coronavirus disease 19 pandemic has likely changed the world in ways not seen in the past. Neutralizing antibody (NAb) assays play an important role in the management of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) outbreak. Using these tools, we can assess the presence and duration of antibody-mediated protection in naturally infected individuals, screen convalescent plasma preparations for donation, test the efficacy of immunotherapy, and analyze NAb titers and persistence after vaccination to predict vaccine-induced protective effects. This review briefly summarizes the various methods used for the detection of SARS-CoV-2 NAbs and compares their advantages and disadvantages to facilitate their development and clinical application.

Performance of anti-SARS-CoV-2 antibody testing in asymptomatic or mild COVID-19 patients: A retrospective study in outbreak on a cruise ship.

OBJECTIVES: A few studies on antibody testing have focused on asymptomatic or mild coronavirus disease 2019 (COVID-19) patients with low initial anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses. Anti-SARS-CoV-2 antibody-testing performance was evaluated using blood samples from asymptomatic or mild COVID-19 patients. METHODS: Blood samples were collected from 143 COVID-19 patients during an outbreak on a cruise ship 3 weeks after diagnosis. Simultaneously, a follow-up SARS-CoV-2 genetic test was performed. Samples stored before the COVID-19 pandemic were also used to evaluate the lateral flow immunochromatographic assay (LFA) and electrochemiluminescence immunoassay (ECLIA). Titers of anti-SARS-CoV-2 IgM and IgG antibodies against the nucleocapsid and spike proteins were measured using the enzyme-linked immunosorbent assay to confirm which antibodies were influenced on LFA- and ECLIA- false-negative result in crew-member samples. RESULTS: Sensitivity, specificity, positive-predictive, and negative-predictive values of LFA-detected IgM antibodies were 0.231, 1.000, 1.000, and 0.613, respectively; those of LFA-detected IgG antibodies were 0.483, 0.989, 0.972, and 0.601, respectively; and those of ECLIA-detected total antibodies were 0.783, 1.000, 1.000, and 0.848, respectively. All antibody titers measured using ELISA were significantly lower in blood samples with negative results than in those with positive results in both LFA and ECLIA. In the patients with negative results from the follow-up genetic testing, IgM-, IgG-, and total-antibody positivity rates were 22.9%, 47.6%, and 72.4%, respectively. CONCLUSIONS: These findings suggest that anti-SARS-CoV-2 antibody testing has lower performance in asymptomatic or mild COVID-19 patients than required in the guidelines.

Agreement between commercially available ELISA and in-house Luminex SARS-CoV-2 antibody immunoassays.

Serological diagnostic of the severe respiratory distress syndrome coronavirus 2 (SARS-CoV-2) is a valuable tool for the determination of immunity and surveillance of exposure to the virus. In the context of an ongoing pandemic, it is essential to externally validate widely used tests to assure correct diagnostics and epidemiological estimations. We evaluated the performance of the COVID-19 ELISA IgG and the COVID-19 ELISA IgM/A (Vircell, S.L.) against a highly specific and sensitive in-house Luminex immunoassay in a set of samples from pregnant women and cord blood. The agreement between both assays was moderate to high for IgG but low for IgM/A. Considering seropositivity by either IgG and/or IgM/A, the technical performance of the ELISA was highly imbalanced, with 96% sensitivity at the expense of 22% specificity. As for the clinical performance, the negative predictive value reached 87% while the positive predictive value was 51%. Our results stress the need for highly specific and sensitive assays and external validation of diagnostic tests with different sets of samples to avoid the clinical, epidemiological and personal disturbances derived from serological misdiagnosis.

Advancements in detection of SARS-CoV-2 infection for confronting COVID-19 pandemics.

As one of the major approaches in combating the COVID-19 pandemics, the availability of specific and reliable assays for the SARS-CoV-2 viral genome and its proteins is essential to identify the infection in suspected populations, make diagnoses in symptomatic or asymptomatic individuals, and determine clearance of the virus after the infection. For these purposes, use of the quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) for detection of the viral nucleic acid remains the most valuable in terms of its specificity, fast turn-around, high-throughput capacity, and reliability. It is critical to update the sequences of primers and probes to ensure the detection of newly emerged variants. Various assays for increased levels of IgG or IgM antibodies are available for detecting ongoing or past infection, vaccination responses, and persistence and for identifying high titers of neutralizing antibodies in recovered individuals. Viral genome sequencing is increasingly used for tracing infectious sources, monitoring mutations, and subtype classification and is less valuable in diagnosis because of its capacity and high cost. Nanopore target sequencing with portable options is available for a quick process for sequencing data. Emerging CRISPR-Cas-based assays, such as SHERLOCK and AIOD-CRISPR, for viral genome detection may offer options for prompt and point-of-care detection. Moreover, aptamer-based probes may be multifaceted for developing portable and high-throughput assays with fluorescent or chemiluminescent probes for viral proteins. In conclusion, assays are available for viral genome and protein detection, and the selection of specific assays depends on the purposes of prevention, diagnosis and pandemic control, or monitoring of vaccination efficacy.

Performance of SARS-CoV-2 serology tests: Are they good enough?

In the emergency of the SARS-CoV-2 pandemic, great efforts were made to quickly provide serology testing to the medical community however, these methods have been introduced into clinical practice without the complete validation usually required by the regulatory organizations. SARS-CoV-2 patient samples (n = 43) were analyzed alongside pre-pandemic control specimen (n = 50), confirmed respiratory infections (n = 50), inflammatory polyarthritis (n = 22) and positive for thyroid stimulating immunoglobulin (n = 30). Imprecision, diagnostic sensitivity and specificity and concordance were evaluated on IgG serologic assays from EuroImmun, Epitope Diagnostics (EDI), Abbott Diagnostics and DiaSorin and a rapid IgG/IgM test from Healgen. EDI and EuroImmun imprecision was 0.02-14.0% CV. Abbott and DiaSorin imprecision (CV) ranged from 5.2%-8.1% and 8.2%-9.6% respectively. Diagnostic sensitivity of the assays was 100% (CI: 80-100%) for Abbott, EDI and EuroImmun and 95% (CI: 73-100%) for DiaSorin at ≥14 days post PCR. Only the Abbott assay had a diagnostic specificity of 100% (CI: 91-100%). EuroImmun cross-reacted in 3 non-SARS-CoV-2 respiratory infections and 2 controls. The DiaSorin displayed more false negative results and cross-reacted in six cases across all conditions tested. EDI had one cross-reactive sample. The Healgen rapid test showed excellent sensitivity and specificity. Overall, concordance of the assays ranged from 76.1% to 97.9%. Serological tests for SARS-CoV-2 showed good analytical performance. The head-to-head analysis of samples revealed differences in results that may be linked to the use of nucleocapsid or spike proteins. The point of care device tested demonstrated adequate performance for antibody detection.

A review on current diagnostic techniques for COVID-19.

INTRODUCTION: SARS-Cov-2 first appeared in Wuhan, China, in December 2019 and spread all over the world soon after that. Given the infectious nature ofSARS-CoV-2, fast and accurate diagnosis tools are important to detect the virus. In this review, we discuss the different diagnostic tests that are currently being implemented in laboratories and provide a description of various COVID-19 kits. AREAS COVERED: We summarize molecular techniques that target the viral load, serological methods used for SARS-CoV-2 specific antibodies detection as well as newly developed faster assays for the detection of SARS-COV 2 in various biological samples. EXPERT OPINION: In the light of the widespread pandemic, the massive diagnosis of COVID-19, using various detection techniques, appears to be the most effective strategy for monitoring and containing its propagation.

Highlighted Prospects of an IgM/IgG Antibodies Test in Identifying Individuals With Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection.

CONTEXT.­: Covert severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections could be seeding new outbreaks. How to identify asymptomatic SARS-CoV-2 infections early has become a global focus. OBJECTIVE.­: To explore the roles of immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies detection, nucleic acid tests, and computed tomography (CT) scanning to identify asymptomatic SARS-CoV-2 infection. DESIGN.­: The clinical data of 389 individuals with close contacts, including in general characteristics, SARS-CoV-2 etiology, serum-specific IgM and IgG antibody detection and CT imaging results, were systematically analyzed. RESULTS.­: The present study showed that only 89 of 389 individuals with close contacts were positive after the first nucleic acid test, while 300 individuals were still negative after 2 nucleic acid tests. Among the 300 individuals, 75 did not have pneumonia, and the other 225 individuals had pulmonary imaging changes. A total of 143 individuals were eventually diagnosed as having asymptomatic infection through IgM antibody and IgG antibody detection. The sensitivity, specificity, and false-negative rate of IgM and IgG antibody detection were approximately 97.1% (347 of 357), 95.3% (204 of 214), and 4.67% (10 of 214), respectively. It also indicated that during approximately 2 weeks, most individuals were both IgM positive and IgG positive, accounting for 68.57% (72 of 105). During approximately 3 weeks, the proportion of IgM-positive and IgG-positive individuals decreased to 8.57% (9 of 105), and the proportion of IgM-negative and IgG-positive individuals increased to 76.19% (80 of 105). CONCLUSIONS.­: There are highlighted prospects of IgM/IgG antibody detection as a preferred method in identifying the individuals with asymptomatic SARS-CoV-2 infection, especially combined with nucleic acid tests and pulmonary CT scanning.

Prevalence and Time Trend of SARS-CoV-2 Infection in Puducherry, India, August-October 2020.

We conducted 3 population-based cross-sectional surveys, at 1-month intervals, to estimate the prevalence and time-trend of severe acute respiratory syndrome coronavirus 2 infection in Puducherry, India. Seropositivity rate increased from 4.9% to 34.5% over 2 months and was 20-fold higher than the number of diagnosed cases of infection.

Detection technologies and recent developments in the diagnosis of COVID-19 infection.

COVID-19 is a disease caused by SARS-CoV-2 capable of causing mild to severe infections in humans. Since its first appearance in China in December 2019, the pandemic has spread rapidly throughout the world. Despite considerable efforts made to contain the disease, the virus has continued its prevalence in many countries with varying degrees of clinical manifestations. To contain this pandemic, collaborative approach involving accurate diagnosis, epidemiology, surveillance, and prophylaxis is essential. However, proper diagnosis using rapid technologies plays a crucial role. With increasing incidence of COVID-19 cases, the accurate and early detection of the SARS-CoV-2 is need of the hour for effective prevention and management of COVID-19 cases as well as to curb its spread. RT-qPCR assay is considered to be the gold standard for the early detection of virus, but this protocol has limited application to use as bedside test because of its technical complexity. To address these challenges, several POC assays have been developed to facilitate the COVID-19 diagnosis outside the centralized testing laboratories as well to accelerate the clinical decision making with a least turnaround time. Hence, in this report, we review different nucleic acid-based and serological techniques available for the diagnosis and effective prevention of COVID-19. KEY POINTS : • Provides comprehensive information on the different diagnostic tools available for COVID-19 • Nucleic acid based tests or antigen detection tests are used for diagnostic purpose • Accurate diagnosis is essential for the efficient management of COVID-19.