Distribution of SARS-CoV-2 PCR Cycle Threshold Values Provide Practical Insight Into Overall and Target-Specific Sensitivity Among Symptomatic Patients

Comparative Analysis of Viral Load and Cytokines during SARS-CoV-2 Infection between Pregnant and Non-Pregnant Women

To better understand the vulnerabilities of pregnant women during the COVID-19 pandemic, we conducted a comprehensive, retrospective cohort study to assess differences in immune responses to SARS-CoV-2 infection between pregnant and non-pregnant women. Nasopharyngeal swabs and serum specimens from 90 pregnant and 278 age-matched non-pregnant women were collected from 15 March 2020 to 23 July 2021 at NewYork-Presbyterian Queens Hospital in New York City. Multiplex reverse transcription polymerase chain reaction, neutralizing antibody, and cytokine array assays were used to assess the incidence, viral load, antibody titers and profiles, and examine cytokine expression patterns. Our results show a lower incidence of SARS-CoV-2 infection in pregnant women compared with non-pregnant women. Pregnant women infected with SARS-CoV-2 exhibited a substantially lower viral load. In addition, the levels of both anti-spike protein receptor-binding domain IgG neutralizing antibodies and anti-N Protein IgG were elevated in pregnant women. Finally, cytokine profiling revealed differential expression of leptin across cohorts. These findings suggest that pregnancy is associated with distinct immune and virological responses to SARS-CoV-2 infection, characterized by lower infection rates, substantially lower viral loads, and enhanced antibody production. Differential cytokine expression indicates unique immune modulation in pregnant women.

SARS-CoV-2 in digital era: Diagnostic techniques and importance of nucleic acid quantification with digital PCRs

Studies related to clinical diagnosis and research of SARS-CoV-2 are important in the current pandemic era. Although molecular biology has emphasised the importance of qualitative analysis, quantitative analysis with nucleic acids in relation to SARS-CoV-2 needs to be clearly emphasised, which can provide perspective for viral dynamic studies of SARS-CoV-2. In this regard, the requirement and utilization of digital PCR in COVID-19 research has substantially increased during the pandemic, necessitating the aggregation of its cardinal applications and future scopes. Hence, this meta-review comprehensively addresses and emphasises the importance of nucleic acid quantification of SARS-CoV-2 RNA with digital PCR (dPCR). Various quantitative techniques of clinical significance like immunological, proteomic and nucleic acid-based diagnosis and quantification, have been comparatively discussed. Furthermore, the core part of the article focusses on the working principle and advantages of digital PCR, along with its applications in COVID-19 research. Several important applications like viral load quantitation, environmental surveillance and assay validation have been extensively investigated and discussed. Certain key future scopes of clinical importance, like mortality prediction, viral/variant-symbiosis, and antiviral studies were also identified, suggesting several possible digital PCR applications in COVID-19 research.

Ct, IL-18 polymorphism, and laboratory biomarkers for predicting chemosensory dysfunctions and mortality in COVID-19

Aim

Patients with COVID-19 often experience chemosensory dysfunction. This research intends to uncover the association of RT-PCR Ct value with chemosensory dysfunctions and SpO2. This study also aims to investigate Ct, SpO2, CRP, D-dimer, and -607 IL-18 T/G polymorphism in order to find out predictors of chemosensory dysfunctions and mortality.

Materials & methods

This study included 120 COVID-19 patients, of which 54 were mild, 40 were severe and 26 were critical. CRP, D-dimer, RT-PCR, and IL-18 polymorphism were evaluated. Results & conclusion: Low Ct was associated with SpO2 dropping and chemosensory dysfunctions. IL-18 T/G polymorphism did not show an association with COVID-19 mortality; conversely, age, BMI, D-dimer and Ct values did.

Post-COVID-19 Syndrome in Outpatients and Its Association with Viral Load

INTRODUCTION

The COVID-19 pandemic is the result of the SARS-CoV-2 virus, which has caused more than 100 million infections and more than 2.5 million deaths worldwide, representing a serious public health problem. The gold method for detecting this virus is qRT-PCR, which is a semiquantitative technique where the viral load can be established through its cycle threshold (Ct). It has also been reported that COVID-19 generates long-term symptoms (post-COVID-19).

METHODS

After three months, a survey was performed on 70 COVID-19 confirmed patients; subsequently, we divided them into four groups (persistent symptoms, chemo-sensitive, cognitive issues, and changes in habit) in order to determine the correlation between viral load and post-COVID-19 symptoms.

RESULTS

Data show that fatigue, nervousness, anosmia, and diet changes are common long-term symptoms; in addition, a negative correlation was found between viral load and the number of post-COVID-19 symptoms.

CONCLUSION

COVID-19 generates long-term symptoms which can cause problems with psychological and social repercussions.

The Relationship Between Population-Level SARS-CoV-2 Cycle Threshold Values and Trend of COVID-19 Infection: Longitudinal Study

BACKGROUND

The distribution of population-level real-time reverse transcription-polymerase chain reaction (RT-PCR) cycle threshold (Ct) values as a proxy of viral load may be a useful indicator for predicting COVID-19 dynamics.

OBJECTIVE

The aim of this study was to determine the relationship between the daily trend of average Ct values and COVID-19 dynamics, calculated as the daily number of hospitalized patients with COVID-19, daily number of new positive tests, daily number of COVID-19 deaths, and number of hospitalized patients with COVID-19 by age. We further sought to determine the lag between these data series.

METHODS

The samples included in this study were collected from March 21, 2021, to December 1, 2021. Daily Ct values of all patients who were referred to the Molecular Diagnostic Laboratory of Iran University of Medical Sciences in Tehran, Iran, for RT-PCR tests were recorded. The daily number of positive tests and the number of hospitalized patients by age group were extracted from the COVID-19 patient information registration system in Tehran province, Iran. An autoregressive integrated moving average (ARIMA) model was constructed for the time series of variables. Cross-correlation analysis was then performed to determine the best lag and correlations between the average daily Ct value and other COVID-19 dynamics-related variables. Finally, the best-selected lag of Ct identified through cross-correlation was incorporated as a covariate into the autoregressive integrated moving average with exogenous variables (ARIMAX) model to calculate the coefficients.

RESULTS

Daily average Ct values showed a significant negative correlation (23-day time delay) with the daily number of newly hospitalized patients (P=.02), 30-day time delay with the daily number of new positive tests (P=.02), and daily number of COVID-19 deaths (P=.02). The daily average Ct value with a 30-day delay could impact the daily number of positive tests for COVID-19 (β=-16.87, P<.001) and the daily number of deaths from COVID-19 (β=-1.52, P=.03). There was a significant association between Ct lag (23 days) and the number of COVID-19 hospitalizations (β=-24.12, P=.005). Cross-correlation analysis showed significant time delays in the average Ct values and daily hospitalized patients between 18-59 years (23-day time delay, P=.02) and in patients over 60 years old (23-day time delay, P<.001). No statistically significant relation was detected in the number of daily hospitalized patients under 5 years old (9-day time delay, P=.27) and aged 5-17 years (13-day time delay, P=.39).

CONCLUSIONS

It is important for surveillance of COVID-19 to find a good indicator that can predict epidemic surges in the community. Our results suggest that the average daily Ct value with a 30-day delay can predict increases in the number of positive confirmed COVID-19 cases, which may be a useful indicator for the health system.

Diagnostic yield and costs associated with a routine pre-operative COVID-19 testing algorithm for asymptomatic patients prior to elective surgery

OBJECTIVES

Infection with COVID-19 presents known and unknown perioperative risks to the patient and operative staff. Pre-operative testing protocols have become widespread, yet little is known about the utility of this practice in asymptomatic patients undergoing elective surgery. We describe the impact and cost of a routine testing protocol on elective surgical procedures in a retrospective series at a single institution.

METHODS

Standardized pre-operative COVID-19 testing in all surgical patients was implemented in May 2020. Health system protocol required testing 3 to 5 days before all elective surgery. Data stratified by surgical specialty were collected over the initial 90-day period and disposition over a period of 6-months was assessed for all positive and indeterminate results.

RESULTS

Thirty-one (0.41%) positive results amongst 7579 pre-procedural tests, including 3 of 792 (0.38%) for urologic procedures, were noted in asymptomatic patients. Following a positive test, 20 procedures (62.5%) were delayed an average of 49 days, 8 were not performed and 3 proceeded without delay. All 3 urologic procedures were delayed a mean of 59 days. Institutional cost per test ranged from $34-$54. The number needed to test for one positive result was 244 with a cost of $11,573 for each positive result.

CONCLUSIONS

Institution of a universal pre-operative COVID-19 screening protocol for asymptomatic, unvaccinated patients undergoing elective surgery identified clinically silent infection in 0.4% of cases with a significant associated cost. Risk and symptom-based testing is likely a better strategy for triaging resources.

Clinical Profiles at the Time of Diagnosis of SARS-CoV-2 Infection in Costa Rica During the Pre-vaccination Period Using a Machine Learning Approach

The clinical manifestations of COVID-19, caused by the SARS-CoV-2, define a large spectrum of symptoms that are mainly dependent on the human host conditions. In Costa Rica, more than 169,000 cases and 2185 deaths were reported during the year 2020, the pre-vaccination period. To describe the clinical presentations at the time of diagnosis of SARS-CoV-2 infection in Costa Rica during the pre-vaccination period, we implemented a symptom-based clustering using machine learning to identify clusters or clinical profiles at the population level among 18,974 records of positive cases. Profiles were compared based on symptoms, risk factors, viral load, and genomic features of the SARS-CoV-2 sequence. A total of 18 symptoms at time of diagnosis of SARS-CoV-2 infection were reported with a frequency > 1%, and those were used to identify seven clinical profiles with a specific composition of clinical manifestations. In the comparison between clusters, a lower viral load was found for the asymptomatic group, while the risk factors and the SARS-CoV-2 genomic features were distributed among all the clusters. No other distribution patterns were found for age, sex, vital status, and hospitalization. In conclusion, during the pre-vaccination time in Costa Rica, the symptoms at the time of diagnosis of SARS-CoV-2 infection were described in clinical profiles. The host co-morbidities and the SARS-CoV-2 genotypes are not specific of a particular profile, rather they are present in all the groups, including asymptomatic cases. In addition, this information can be used for decision-making by the local healthcare institutions (first point of contact with health professionals, case definition, or infrastructure). In further analyses, these results will be compared against the profiles of cases during the vaccination period.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43657-022-00058-x.

Relevance of cycle threshold values in mass screening by reverse-transcription-PCR during COVID-19 pandemic in Belgium: a decision-making support?

Aim: The Belgium’s strategy against COVID-19 was partly based on mass screening. Here, we reported the results observed in a Belgian mass screening center. Materials & methods: Between October 2020 and February 2021, 32,089 samples were collected analyzed with reverse-transcription PCR (Thermo Fisher Scientific kits and apparatus). Patients were categorized according to their contagiousness (extrapolated from the cycle threshold [Ct] values and the recommendation of Sciensano). Results: We observed association between Ct values and age, with higher Ct observed in extreme age groups (<6 years and >75 years). Conclusion: The analysis of the evolution of the contagiousness of these patients tested twice within a 7-day period showed the relevancy of the recommendation edited by Sciensano.

The Belgium’s strategy against COVID-19 was partly based on mass screening performed with reverse-transcription PCR analysis performed on nasopharyngeal samples. Reverse-transcription PCR allows the detection of individuals infected by the virus. In addition, it provides semi quantitative results correlated to the quantity of virus present in the patient, these results are difficult to interpret for the patients and numerous practitioners. In our study, we showed that the interpretation of these results should take into account the age of the patients. We also showed that the semi quantitative result observed in a positive patient is not predictive of the evolution of the viral load (quantity of virus present in the organism) in the 7 following days.

Potential risk of SARS-CoV-2 infection among people handling linens used by COVID-19 patients before and after washing

The risk of SARS-CoV-2 infection when people handle linens is uncertain. We examined the presence of SARS-CoV-2 on linens, in the air, and on personal protective equipment (PPE) to assess potential infection risk among individuals who handle linens used by SARS-CoV-2-infected people. Patients in a hospital and an accommodation facility who tested positive for SARS-CoV-2 participated in this study in 2020. Linen samples before washing or disinfection, rinse water after washing or disinfection, air in the workplace at the hospital and an accommodation facility, and the PPE worn by linen-handling people were tested for SARS-CoV-2 RNA and viable viruses. Among 700 samples from 13 SARS-CoV-2-infected participants and their surrounding environment, SARS-CoV-2 RNA was detected from 14% (52/362) of the linens used by COVID-19 patients (cycle threshold [Ct] value: 33-40). SARS-CoV-2 RNA was detected from 8% (2/26) of rinse water after washing or disinfection, from 15% (16/104) of air samples in the workspace, and from 10% (5/52) of gowns worn by linen-handling people, all with high Ct values (> 36). No SARS-CoV-2 was isolated from any samples. The potential risk of SARS-CoV-2 infection from handling linens used by SARS-CoV-2-infected people exists but appears to below.

Clinical evaluation of Sofia Rapid Antigen Assay for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among emergency department to hospital admissions

OBJECTIVE

To determine the utility of the Sofia SARS rapid antigen fluorescent immunoassay (FIA) to guide hospital-bed placement of patients being admitted through the emergency department (ED).

DESIGN

Cross-sectional analysis of a clinical quality improvement study.

SETTING

This study was conducted in 2 community hospitals in Maryland from September 21, 2020, to December 3, 2020. In total, 2,887 patients simultaneously received the Sofia SARS rapid antigen FIA and SARS-CoV-2 RT-PCR assays on admission through the ED.

METHODS

Rapid antigen results and symptom assessment guided initial patient placement while confirmatory RT-PCR was pending. The sensitivity, specificity, positive predictive values, and negative predictive values of the rapid antigen assay were calculated relative to RT-PCR, overall and separately for symptomatic and asymptomatic patients. Assay sensitivity was compared to RT-PCR cycle threshold (Ct) values. Assay turnaround times were compared. Clinical characteristics of RT-PCR-positive patients and potential exposures from false-negative antigen assays were evaluated.

RESULTS

For all patients, overall agreement was 97.9%; sensitivity was 76.6% (95% confidence interval [CI], 71%-82%), and specificity was 99.7% (95% CI, 99%-100%). We detected no differences in performance between asymptomatic and symptomatic individuals. As RT-PCR Ct increased, the sensitivity of the antigen assay decreased. The mean turnaround time for the antigen assay was 1.2 hours (95% CI, 1.0-1.3) and for RT-PCR it was 20.1 hours (95% CI, 18.9-40.3) (P < .001). No transmission from antigen-negative/RT-PCR-positive patients was identified.

CONCLUSIONS

Although not a replacement for RT-PCR for detection of all SARS-CoV-2 infections, the Sofia SARS antigen FIA has clinical utility for potential initial timely patient placement.

CRISPR-based point-of-care diagnostics incorporating Cas9, Cas12, and Cas13 enzymes advanced for SARS-CoV-2 detection

An outbreak of the novel beta coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first came to light in December 2019, which has unfolded rapidly and turned out to be a global pandemic. Early prognosis of viral contamination involves speedy intervention, disorder control, and good-sized management of the spread of disease. Reverse transcription-polymerase chain reaction, considered the gold standard test for detecting nucleic acids and pathogen diagnosis, provides high sensitivity and specificity. However, reliance on high-priced equipped kits, associated reagents, and skilled personnel slow down sickness detection. Lately, the improvement of clustered regularly interspaced short palindromic repeat (CRISPR)-Cas (CRISPR-associated protein)-based diagnostic systems has reshaped molecular diagnosis due to their low cost, simplicity, speed, efficiency, high sensitivity, specificity, and versatility, which is vital for accomplishing point-of-care diagnostics. We reviewed and summarized CRISPR-Cas-based point-of-care diagnostic strategies and research in these paintings while highlighting their characteristics and challenges for identifying SARS-CoV-2.

Antibody Response to SARS-CoV-2 in the First Batch of COVID-19 Patients in China by a Self-Developed Rapid IgM-IgG Test

It has been over two years since the COVID-19 pandemic began and it is still an unprecedented global challenge. Here, we aim to characterize the antibody profile from a large batch of early COVID-19 cases in China, from January – March 2020. More than 1,000 serum samples from participants in Hubei and Zhejiang province were collected. A series of serum samples were also collected along the disease course from 70 patients in Shanghai and Chongqing for longitudinal analysis. The serologic assay (ALLtest) we developed was confirmed to have high sensitivity (92.58% - 97.55%) and high specificity (92.14% - 96.28%) for the detection of SARS-CoV-2 nucleocapsid-specific antibodies. Confirmed cases found in the Hubei Provincial Center for Disease Control and Prevention (HBCDC), showed a significantly (p = 0.0018) higher positive rate from the ALLtest than RNA test. Then, we further identified the disease course, age, sex, and symptoms that were correlating factors with our ALLtest results. In summary, we confirmed the high reliability of our ALLtest and its important role in COVID-19 diagnosis. The correlating factors we identified will require special attention during future clinical application.

Elucidation of correlation between SARS-CoV-2 RdRp and N gene cycle threshold (Ct) by RT-PCR with age and gender

Background

Coronavirus disease 2019 (COVID19) caused by the new severe acute respiratory syndrome coronavirus 2 (SARSCoV2) is a global public health emergency. Age and gender are two important factors related to the risk and outcome of various diseases. Cycle threshold (Ct) value is believed to have relation with age and gender.

Objective

This study has been conducted to investigates the association between SARS-CoV-2 cycle threshold to age and gender of COVID-19 patients, to investigate whether the population-wide change of SARSCoV2 RTPCR Ct value over time is corelated to the number of new COVID19 cases and to investigate the dynamic of RdRp and N genes.

Methods

72,811 individuals from second wave of COVID19, were observed in current study at Pure Health Lab, Mafraq Hospital, Abu Dhabi, UAE.

Results

15,201/72,811 (21 %) positivity was observed. COVID-19 were more prevalent in males (59.35%) as compared to female (40.65%). The Positivity rate were significantly higher in Male than in Female cases (p-Value = 0.04). The Ct values for both targets of all the samples were ranged from 4.57 to 29.73. Longitudinal analysis showed significant increased during the study period from starting to end as were hypothesized. Interestingly, both the targets (RdRp and N) were present in age < 1 year. Which may indicate that mutated strains are not prevalent in children’s < 1 year.

Conclusion

There was no statistically significant difference in viral loads in between age-groups. Males were tending to higher viral load compared to females. The findings have implications for preventive strategies.

Rapid, adaptable and sensitive Cas13-based COVID-19 diagnostics using ADESSO

During the ongoing COVID-19 pandemic, PCR testing and antigen tests have proven critical for helping to stem the spread of its causative agent, SARS-CoV-2. However, these methods suffer from either general applicability and/or sensitivity. Moreover, the emergence of variant strains creates the need for flexibility to correctly and efficiently diagnose the presence of substrains. To address these needs we developed the diagnostic test ADESSO (Accurate Detection of Evolving SARS-CoV-2 through SHERLOCK (Specific High Sensitivity Enzymatic Reporter UnLOCKing) Optimization) which employs Cas13 to diagnose patients in 1 h without sophisticated equipment. Using an extensive panel of clinical samples, we demonstrate that ADESSO correctly identifies infected individuals at a sensitivity and specificity comparable to RT-qPCR on extracted RNA and higher than antigen tests for unextracted samples. Altogether, ADESSO is a fast, sensitive and cheap method that can be applied in a point of care setting to diagnose COVID-19 and can be quickly adjusted to detect new variants.

COVID-19 Cycle Threshold/Cycle Number Testing at a Community Living Center

BACKGROUND

COVID-19 imposes a special risk to the nursing home population, including community living centers (CLCs) for veterans. Cycle threshold/cycle number (CT/CN) values obtained by serial reverse transcriptase polymerase chain reaction (RT-PCR) testing could yield valuable information about viral load and potential infectiousness. Serial testing for COVID-19 with CT/CN correlates in a nursing home population during an outbreak has not yet been reported in the literature.

METHODS

A retrospective review of serial RT-PCR testing for COVID-19 during an outbreak at a CLC was performed from March 28 to April 4, 2020, with follow-up of identified patients until November 10, 2020. Testing was performed on the Abbot m2000 or Cepheid platform.

RESULTS

Of 80 patients tested, 25 (31%) were positive for COVID-19. CT/CN values corresponded to the infection course as expected.

CONCLUSIONS

Repeat testing for COVID-19 accompanied by CT/CN values could provide clinical and epidemiologic information about the likely stage of the patients' disease course, which may aid public health measures and clinical management.

A random priming amplification method for whole genome sequencing of SARS-CoV-2 virus

BACKGROUND

Non-targeted whole genome sequencing is a powerful tool to comprehensively identify constituents of microbial communities in a sample. There is no need to direct the analysis to any identification before sequencing which can decrease the introduction of bias and false negatives results. It also allows the assessment of genetic aberrations in the genome (e.g., single nucleotide variants, deletions, insertions and copy number variants) including in noncoding protein regions.

METHODS

The performance of four different random priming amplification methods to recover RNA viral genetic material of SARS-CoV-2 were compared in this study. In method 1 (H-P) the reverse transcriptase (RT) step was performed with random hexamers whereas in methods 2-4 RT incorporating an octamer primer with a known tag. In methods 1 and 2 (K-P) sequencing was applied on material derived from the RT-PCR step, whereas in methods 3 (SISPA) and 4 (S-P) an additional amplification was incorporated before sequencing.

RESULTS

The SISPA method was the most effective and efficient method for non-targeted/random priming whole genome sequencing of SARS-CoV-2 that we tested. The SISPA method described in this study allowed for whole genome assembly of SARS-CoV-2 and influenza A(H1N1)pdm09 in mixed samples. We determined the limit of detection and characterization of SARS-CoV-2 virus which was 103 pfu/ml (Ct, 22.4) for whole genome assembly and 101 pfu/ml (Ct, 30) for metagenomics detection.

CONCLUSIONS

The SISPA method is predominantly useful for obtaining genome sequences from RNA viruses or investigating complex clinical samples as no prior sequence information is needed. It might be applied to monitor genomic virus changes, virus evolution and can be used for fast metagenomics detection or to assess the general picture of different pathogens within the sample.

Evaluation of efficiency and sensitivity of 1D and 2D sample pooling strategies for SARS-CoV-2 RT-qPCR screening purposes

To increase the throughput, lower the cost, and save scarce test reagents, laboratories can pool patient samples before SARS-CoV-2 RT-qPCR testing. While different sample pooling methods have been proposed and effectively implemented in some laboratories, no systematic and large-scale evaluations exist using real-life quantitative data gathered throughout the different epidemiological stages. Here, we use anonymous data from 9673 positive cases to model, simulate and compare 1D and 2D pooling strategies. We show that the optimal choice of pooling method and pool size is an intricate decision with a testing population-dependent efficiency-sensitivity trade-off and present an online tool to provide the reader with custom real-time 1D pooling strategy recommendations.

False-negative rate of SARS-CoV-2 RT-PCR tests and its relationship to test timing and illness severity: A case series

Objective

To determine the false-negative rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse-transcription polymerase chain reaction (RT-PCR) test results, and to describe the characteristics of coronavirus disease 2019 (COVID-19) patients with false-negative results.

Methods

We validated SARS-CoV-2-positive RT-PCR test results performed in hospitalized patients between February 1 and August 31, 2020 and classified the patients according to disease severity.

Results

In total, 2038 SARS-CoV-2 RT-PCR tests were performed on 1890 patients. Of these, 145 patients had positive results and were diagnosed with COVID-19. Among the 145 patients with COVID-19, the initial RT-PCR tests were negative in five patients. Of these, three had moderate illness and were initially tested in the early stage of disease, and two had severe illness and were initially tested in the late stage of disease, when RT-PCR testing has lower sensitivity due to viral clearance.

Conclusions

These findings suggest that false-negative results can be caused by both observer errors and by low viral RNA levels in the later stages of disease, after the infection has cleared. Clinicians should be aware that patients with COVID-19 can have negative RT-PCR test results in the later stages of infection.

•

All SARS-CoV-2 RT-PCR test results of hospitalized COVID-19 patients were reviewed.

•

Of 145 confirmed COVID-19 cases, 5 (3.45%) had a negative first RT-PCR test result.

•

Of the 5 patients, 3 with moderate disease first tested soon after symptom onset.

•

The initial testing was delayed in 2 patients with severe/critical disease.

•

False-negative results can occur in deteriorating patients who have delayed testing.

Importance of sample input volume for accurate SARS-CoV-2 qPCR testing

Nucleic acid testing is the most widely used detection method for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic. Currently, a number of COVID-19 real-time quantitative reverse transcription PCR (qPCR) kits with high sensitivity and specificity are available for SARS-CoV-2 testing. However, these qPCR assays are not always reliable in detecting low viral load samples (Ct-value ≥ 35), resulting in inconclusive or false-negative results. Here, we used a Poisson distribution to illustrate the inconsistent performance of qPCR tests in detecting low viral load samples. From this, we concluded that the false-negative outcomes resulted from the random occurrences of sampling zero target molecules in a single test, and the probability to sample zero target molecules in one test decreased significantly with increasing purified RNA or initial sample input volume. At a given RNA concentration of 0.5 copy/μL, the probability of sampling zero RNA molecules decreased from 36.79% to close to 0.67% after increasing the RNA input volume from 2 to 10 μL. A SARS-CoV-2 qPCR assay with an LOD of 300 copies/mL was used to validate the improved consistency of the qPCR tests. We found that the false-negative qPCR results of clinical COVID-19 samples with a Ct ≥ 35 decreased by 50% after increasing the input of purified RNA from 2 to 10 μL. The consistency, accuracy, and robustness of nucleic acid testing for SARS-CoV-2 samples with low viral loads can be improved by increasing the sample input volume.

Effectiveness and Use of RT‐PCR Point of Care Testing in a Large‐Scale COVID ‐19 Surveillance System

Background

Rapid COVID‐19 testing platforms can identify infected individuals at the point of care (POC), allowing immediate isolation of infected individuals and reducing the risk of transmission. While lab‐based nucleic acid amplification testing (NAAT) is often considered the gold standard to detect SARS‐CoV‐2 in the community, results typically take 2–7 days to return, rendering POC testing a critical diagnostic tool for infection control. The National Football League (NFL) and NFL Players Association deployed a new POC testing strategy using a newly available reverse transcriptase polymerase chain reaction (RT‐PCR) rapid test during the 2020 season, and evaluated diagnostic effectiveness compared to other available devices using real‐world population surveillance data.

Methods

RT‐PCR POC test results were compared to NAAT results from same‐day samples by calculation of positive and negative concordance. Sensitivity analyses were performed for three subgroups: (1) individuals symptomatic at time of positive test; (2) individuals tested during the pilot phase of rollout; and (3) individuals tested daily.

Results

Among 4989 same‐day POC/NAAT pairs, 4957 (99.4%) were concordant, with 93.1% positive concordance and 99.6% negative concordance. Based on adjudicated case status, the false negative rate was 0.2% and false positive rate was 2.9%. In 43 instances, the immediate turnaround of results by POC allowed isolation of infected individuals 1 day sooner than lab‐based testing. Positive/negative concordance in sensitivity analyses were relatively stable.

Conclusion

RT‐PCR POC testing provided timely results that were highly concordant with lab‐based NAAT in population surveillance. Expanded use of effective RT‐PCR POC can enable rapid isolation of infected individuals and reduce COVID‐19 infection in the community.

SARS-CoV-2 viral-load distribution reveals that viral loads increase with age: a retrospective cross-sectional cohort study

BACKGROUND

Describing the SARS-CoV-2 viral-load distribution in different patient groups and age categories.

METHODS

All results from first nasopharyngeal (NP) and oropharyngeal (OP) swabs from unique patients tested via SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) collected between 1 January and 1 December 2020 predominantly in the Public Health Services regions Kennemerland and Hollands Noorden, province of North Holland, the Netherlands, were included in this study. SARS-CoV-2 PCR crossing-point (Cp)-values were used to estimate viral loads.

RESULTS

In total, 278 455 unique patients were tested, of whom 9.1% (n = 25.374) were SARS-CoV-2-positive. PCRs performed by Public Health Services (n = 211 914), in which sampling and inclusion were uniform, revealed a clear relation between age and SARS-CoV-2 viral load, with especially children aged <12 years showing lower viral loads than adults (β: -0.03, 95% confidence interval: -0.03 to -0.02, p < 0.001), independently of sex and/or symptom duration. Interestingly, the median Cp-values between the >79- and <12-year-old populations differed by more than four PCR cycles, suggesting an ∼16-fold difference in viral load. In addition, the proportion of children aged <12 years with a low load (Cp-value >30) was higher compared with other patients (31.1% vs 17.2%, p-value < 0.001).

CONCLUSIONS

In patients tested by Public Health Services, SARS-CoV-2 viral load increases with age. Further studies should elucidate whether the lower viral load in children is indeed related to their suggested limited role in SARS-CoV-2 transmission. Moreover, as rapid antigen tests are less sensitive than PCR, these results suggest that SARS-CoV-2 antigen tests have lower sensitivity in children than in adults.

Antigen Test Performance Among Children and Adults at a SARS-CoV-2 Community Testing Site

BACKGROUND

Performance characteristics of SARS-CoV-2 antigen tests among children are limited despite the need for point-of-care testing in school and childcare settings. We describe children seeking SARS-CoV-2 testing at a community site and compare antigen test performance to real-time reverse transcription-polymerase chain reaction (RT-PCR) and viral culture.

METHODS

Two anterior nasal specimens were self-collected for BinaxNOW antigen and RT-PCR testing, along with demographics, symptoms, and exposure information from individuals ≥5 years at a community testing site. Viral culture was attempted on residual antigen or RT-PCR-positive specimens. Demographic and clinical characteristics, and the performance of SARS-CoV-2 antigen tests, were compared among children (<18 years) and adults.

RESULTS

About 1 in 10 included specimens were from children (225/2110); 16.4% (37/225) were RT-PCR-positive. Cycle threshold values were similar among RT-PCR-positive specimens from children and adults (22.5 vs 21.3, P = .46) and among specimens from symptomatic and asymptomatic children (22.5 vs 23.2, P = .39). Sensitivity of antigen test compared to RT-PCR was 73.0% (27/37) among specimens from children and 80.8% (240/297) among specimens from adults; among specimens from children, specificity was 100% (188/188), positive and negative predictive values were 100% (27/27) and 94.9% (188/198), respectively. Virus was isolated from 51.4% (19/37) of RT-PCR-positive pediatric specimens; all 19 had positive antigen test results.

CONCLUSIONS

With lower sensitivity relative to RT-PCR, antigen tests may not diagnose all positive COVID-19 cases; however, antigen testing identified children with live SARS-CoV-2 virus.

Active environmental surveillance of SARS-CoV-2 in Midwestern United States meatpacking plants

This pilot project investigated environmental SARS-CoV-2 presence in seven Midwestern meatpacking plants from May 2020 to January 2021. This study investigated social distancing and infection control practices and incorporated environmental sampling of surfaces and air in employee common areas. All plants increased their social distancing efforts, increased the frequency of cleaning and disinfecting worker areas, and screened for symptomatic people to prevent entry into the workplace. 575 samples from common areas were collected and evaluated with RT-qPCR for the presence of SARS-CoV-2. 42/367 surface samples were positive, while no virus was detected in air samples. Case positive data from the counties surrounding each plant showed peak positive SARS-CoV-2 cases from 12-55 days before the virus was detected in the plant, indicating that environmental sampling is likely a lagging indicator of community and plant infection.

The Dangers of Using Cq to Quantify Nucleic Acid in Biological Samples: A Lesson From COVID-19

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA quantities, measured by reverse transcription quantitative PCR (RT-qPCR), have been proposed to stratify clinical risk or determine analytical performance targets. We investigated reproducibility and how setting diagnostic cutoffs altered the clinical sensitivity of coronavirus disease 2019 (COVID-19) testing.

METHODS

Quantitative SARS-CoV-2 RNA distributions [quantification cycle (Cq) and copies/mL] from more than 6000 patients from 3 clinical laboratories in United Kingdom, Belgium, and the Republic of Korea were analyzed. Impact of Cq cutoffs on clinical sensitivity was assessed. The June/July 2020 INSTAND external quality assessment scheme SARS-CoV-2 materials were used to estimate laboratory reported copies/mL and to estimate the variation in copies/mL for a given Cq.

RESULTS

When the WHO-suggested Cq cutoff of 25 was applied, the clinical sensitivity dropped to about 16%. Clinical sensitivity also dropped to about 27% when a simulated limit of detection of 106 copies/mL was applied. The interlaboratory variation for a given Cq value was >1000 fold in copies/mL (99% CI).

CONCLUSION

While RT-qPCR has been instrumental in the response to COVID-19, we recommend Cq (cycle threshold or crossing point) values not be used to set clinical cutoffs or diagnostic performance targets due to poor interlaboratory reproducibility; calibrated copy-based units (used elsewhere in virology) offer more reproducible alternatives. We also report a phenomenon where diagnostic performance may change relative to the effective reproduction number. Our findings indicate that the disparities between patient populations across time are an important consideration when evaluating or deploying diagnostic tests. This is especially relevant to the emergency situation of an evolving pandemic.

UnCovid: A versatile, low-cost, and open-source protocol for SARS-CoV-2 RNA detection

Here, we describe a detailed step-by-step protocol to detect SARS-CoV-2 RNA using RT-PCR-mediated amplification and CRISPR/Cas-based visualization. The optimized assay uses basic molecular biology equipment such as conventional thermocyclers and transilluminators for qualitative detection. Alternatively, a fluorescence plate reader can be used for quantitative measurements. The protocol detects two regions of the SARS-CoV-2 genome in addition to the human RNaseP sample control. Aiming to reach remote regions, this work was developed to use the portable molecular workstation from BentoLab. For complete details on the use and execution of this protocol, please refer to Alcántara et al., 2021.

Handheld Microfluidic Filtration Platform Enables Rapid, Low-Cost, and Robust Self-Testing of SARS-CoV-2 Virus

Here, a novel microfluidic test kit combining ultrahigh throughput hydrodynamic filtration and sandwich immunoassay is reported. Specifically, nano and microbeads coated with two different, noncompetitive antibodies, are used to capture the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) proteins simultaneously, forming larger complexes. Microfluidic filtration discards free nanobeads but retains antigen-bridged complexes in the observation zone, where a display of red color indicates the presence of antigen in the sample. This testing platform exhibits high throughput separation (<30 s) and enrichment of antigen that exceeds the traditional lateral flow assays or microfluidic assays, with a low limit of detection (LoD) < 100 copies mL-1 . In two rounds of clinical trials conducted in December 2020 and August 2021, the assays demonstrate high sensitivities of 95.4% and 100%, respectively, which proves this microfluidic test kit is capable of detecting SARS-CoV-2 virus variants evolved over significant periods of time. Furthermore, the mass-produced chip can be fabricated at a cost of $0.98/test and the robust design allows the chip to be reused for over 50 times. All of these features make the microfluidic test kit particularly suitable for areas with inadequate medical infrastructure and a shortage of laboratory resources.

SNP and Phylogenetic Characterization of Low Viral Load SARS-CoV-2 Specimens by Target Enrichment

Background: Surveillance of SARS-CoV-2 across the globe has enabled detection of new variants and informed the public health response. With highly sensitive methods like qPCR widely adopted for diagnosis, the ability to sequence and characterize specimens with low titers needs to keep pace.

Methods: Nucleic acids extracted from nasopharyngeal swabs collected from four sites in the United States in early 2020 were converted to NGS libraries to sequence SARS-CoV-2 genomes using metagenomic and xGen target enrichment approaches. Single nucleotide polymorphism (SNP) analysis and phylogeny were used to determine clade assignments and geographic origins of strains.

Results: SARS-CoV-2-specific xGen enrichment enabled full genome coverage for 87 specimens with Ct values &lt;29, corresponding to viral loads of &gt;10,000 cp/ml. For samples with viral loads between 103 and 106 cp/ml, the median genome coverage for xGen was 99.1%, sequence depth was 605X, and the “on-target” rate was 57 ± 21%, compared to 13%, 2X and 0.001 ± 0.016%, respectively, for metagenomic sequencing alone. Phylogenetic analysis revealed the presence of most clades that existed at the time of the study, though clade GH dominated in the Midwest.

Conclusions: Even as vaccines are being widely distributed, a high case load of SARS-CoV-2 infection persists around the world. Viral genetic surveillance has succeeded in warning the public of new variants in circulation and ensured that diagnostic tools remain resilient to a steadily increasing number of mutations. Target capture offers a means of characterizing low viral load samples which would normally pose a challenge for metagenomic sequencing.

Unlocking SARS-CoV-2 detection in low- and middle-income countries

Low- and middle-income countries (LMICs) are significantly affected by SARS-CoV-2, partially due to their limited capacity for local production and implementation of molecular testing. Here, we provide detailed methods and validation of a molecular toolkit that can be readily produced and deployed using laboratory equipment available in LMICs. Our results show that lab-scale production of enzymes and nucleic acids can supply over 50,000 tests per production batch. The optimized one-step RT-PCR coupled to CRISPR-Cas12a-mediated detection showed a limit of detection of 102 ge/μL in a turnaround time of 2 h. The clinical validation indicated an overall sensitivity of 80%-88%, while for middle and high viral load samples (Cq ≤ 31) the sensitivity was 92%-100%. The specificity was 96%-100% regardless of viral load. Furthermore, we show that the toolkit can be used with the mobile laboratory Bento Lab, potentially enabling LMICs to implement detection services in unattended remote regions.

Virus load and incidence of olfactory, gustatory, respiratory, gastrointestinal disorders in COVID-19 patients: A retrospective cohort study

OBJECTIVES

This study investigated the relationship between viral load and the incidence of olfactory and gustatory dysfunction (OD and GD), the incidence of respiratory and gastrointestinal symptoms and the recovery of OD and GD in COVID-19 patients.

DESIGN

A retrospective cohort study.

SETTING AND PARTICIPANTS

This study was conducted on 599 outpatients' cases in Golestan province between February and June 2020.

MAIN OUTCOME MEASURES

The incidence, severity (complete or partial) and recovery time of OD and GD and their associations with cycle threshold (CT) values of SARS-CoV-2 polymerase chain reaction were assessed.

RESULTS

The mean age of patients was 38.27 ± 13.62 years. The incidence of general symptoms included myalgia 70.1%, headache 51.8%, fever 47.7% and dyspnoea 21.4%. 41.9% of patients had gastrointestinal symptoms, including abdominal pain 26.5%, diarrhoea 25.2%, nausea 20.5% and vomiting 12.9%. 12.2% of patients had comorbidity. The trimester recovery rates of OD and GD were 93.94% and 94.74% respectively. The mean recovery time of OD and GD was 14.56 ± 13.37 and 13.8 ± 3.77 days respectively. The mean CT value in all patients was 27.45 ± 4.55. There were significant associations between the mean of CT value with headache (p = 0.04), GD (p = 0.002) and OD (p = 0.001).

CONCLUSIONS

The finding of this study indicates a possible association between viral load with incidence of OD and GD in COVID-19 patient's cases and assures the recovery of OD/GD in these patients.

Artificial Intelligence and Mapping a New Direction in Laboratory Medicine: A Review

BACKGROUND

Modern artificial intelligence (AI) and machine learning (ML) methods are now capable of completing tasks with performance characteristics that are comparable to those of expert human operators. As a result, many areas throughout healthcare are incorporating these technologies, including in vitro diagnostics and, more broadly, laboratory medicine. However, there are limited literature reviews of the landscape, likely future, and challenges of the application of AI/ML in laboratory medicine.

CONTENT

In this review, we begin with a brief introduction to AI and its subfield of ML. The ensuing sections describe ML systems that are currently in clinical laboratory practice or are being proposed for such use in recent literature, ML systems that use laboratory data outside the clinical laboratory, challenges to the adoption of ML, and future opportunities for ML in laboratory medicine.

SUMMARY

AI and ML have and will continue to influence the practice and scope of laboratory medicine dramatically. This has been made possible by advancements in modern computing and the widespread digitization of health information. These technologies are being rapidly developed and described, but in comparison, their implementation thus far has been modest. To spur the implementation of reliable and sophisticated ML-based technologies, we need to establish best practices further and improve our information system and communication infrastructure. The participation of the clinical laboratory community is essential to ensure that laboratory data are sufficiently available and incorporated conscientiously into robust, safe, and clinically effective ML-supported clinical diagnostics.

Distribution of cycle threshold values in RT-qPCR tests during the autumn 2020 peak of the COVID-19 pandemic in the Czech Republic

Reverse-transcription quantitative PCR (RT-qPCR) is currently the most sensitive method to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19). We analysed 1927 samples collected in a local public hospital during the autumn 2020 peak of the pandemic in the Czech Republic. The tests were performed using the Seegene Allplex 2019-nCov assay, which simultaneously detects three SARS-CoV-2 genes. In all samples analysed, 44.5 % were negative for all three genes, and 37.6 % were undoubtedly positive, with all three viral genes being amplified. A high degree of correlation between C_t values among the genes confirmed the internal consistency of testing. Most of the positive samples were detected between the 15th and 35th cycles. We also registered a small number of samples with only one (13.2 %) or two (4.7 %) amplified genes, which may have originated from either freshly infected or already recovering patients. In addition, we did not detect any potentially false-positive samples from low-prevalence settings. Our results document that PCR testing represents a reliable and robust method for routine diagnostic detection of SARS-CoV-2.

A Real-World Comparison of SARS-CoV-2 Rapid Antigen vs. Polymerase Chain Reaction Testing in Florida

Background The reported sensitivity of rapid, antigen-based diagnostics for SARS-CoV-2 infection varies. Few studies have evaluated rapid antigen tests in real-world settings or among large populations. Methods Beginning October 2020, Florida offered individuals presenting for SARS-CoV-2 testing polymerase chain reaction (PCR) testing if they tested positive by the Abbott BinaxNOW^TM COVID-19 Ag Card, were symptomatic, or required or requested PCR testing. We compared test results among individuals who received both types of tests at four publicly-accessible testing sites across Florida. We calculated the positive percent agreement (PPA) between the two test types by symptom status. Subsequently, we evaluated the PPA among individuals regardless of symptoms with lower cycle threshold values (<30). Results Overall, 18,457 individuals were tested via both methods, of which 3,153 (17.1%) were positive by PCR. The PPA for the Abbott BinaxNOW^TM COVID-19 Ag Card using the PCR comparator was 49.2% (95% CI 47.4%-50.9%). That performance was moderately improved among symptomatic individuals (51.9%; 95% CI 49.7%-54.0%). When restricted to positive PCR tests with a cycle threshold value <30, regardless of symptom status, the PPA was 75.3% (95% CI 72.8%-77.6%). Conclusion The PPA of the Abbott BinaxNOW^TM COVID-19 Ag Card with PCR was lower than among previous reports. Our findings may reflect the performance of the BinaxNOW^TM antigen test in real-world settings.

High concentrations of hypochlorous acid-based disinfectant in the environment reduced the load of SARS-CoV-2 in nucleic acid amplification testing

During the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic, chlorine-containing disinfectants have been widely used in nucleic acid amplification testing laboratories. Whether the use of disinfectants affect the results of viral nucleic acid amplification is unknown. We examined the impact of different hypochlorous acid (HOCl) concentrations on the quantitative results of SARS-CoV-2 by real-time reverse-transcription polymerase chain reaction (RT-PCR). We also explored the mechanisms and models of action of chlorine-containing disinfectants that affected the detection of SARS-CoV-2. The results showed that different HOCl concentrations and different action times had an impact on the SARS-CoV-2 results. High concentrations of ambient HOCl have a greater impact than low concentrations, and this effect will increase with the extension of the action time and with the increase in ambient humidity. Compared with the enzymes or the extracted RNA required for RT-PCR, the impact of HOCl on the SARS-CoV-2 detection is more likely to be caused by damage to primers and probes in the PCR system. The false negative result still existed after changing the ambient disinfectant to ethanol but not peracetic acid. The use of HOCl in the environment will have an unpredictable impact on the nucleic acid test results of SARS-CoV-2. In order to reduce the possibility of false negative of SARS-CoV-2 nucleic acid test and prevent the spread of epidemic disease, environmental disinfectants should be used at the beginning and end of the experiment rather than during the experimental operation.

Optimizing SARS-CoV-2 Surveillance in the United States: Insights From the National Football League Occupational Health Program

BACKGROUND

Evidence to understand effective strategies for surveillance and early detection of SARS-CoV-2 is limited.

OBJECTIVE

To describe the results of a rigorous, large-scale COVID-19 testing and monitoring program.

DESIGN

The U.S. National Football League (NFL) and the NFL Players Association (NFLPA) instituted a large-scale COVID-19 monitoring program involving daily testing using 2 reverse transcription polymerase chain reaction (RT-PCR) platforms (Roche cobas and Thermo Fisher QuantStudio), a transcription-mediated amplification platform (Hologic Panther), and an antigen point-of-care (aPOC) test (Quidel Sofia).

SETTING

32 NFL clubs in 24 states during the 2020 NFL season.

PARTICIPANTS

NFL players and staff.

MEASUREMENTS

SARS-CoV-2 test results were described in the context of medically adjudicated status. Cycle threshold (Ct) values are reported when available.

RESULTS

A total of 632 370 tests administered across 11 668 persons identified 270 (2.4%) COVID-19 cases from 1 August to 14 November 2020. Positive predictive values ranged from 73.0% to 82.0% across the RT-PCR platforms. High Ct values (33 to 37) often indicated early infection. For the first positive result, the median Ct value was 32.77 (interquartile range, 30.02 to 34.72) and 22% of Ct values were above 35. Among adjudicated COVID-19 cases tested with aPOC, 42.3% had a negative result. Positive concordance between aPOC test result and adjudicated case status increased as viral load increased.

LIMITATIONS

Platforms varied by laboratory, and test variability may reflect procedural differences.

CONCLUSION

Routine RT-PCR testing allowed early detection of infection. Cycle threshold values provided a useful guidepost for understanding results, with high values often indicating early infection. Antigen POC testing was unable to reliably rule out COVID-19 early in infection.

PRIMARY FUNDING SOURCE

The NFL and the NFLPA.

Comparison of Six SARS-CoV-2 Molecular Methods and Correlation with the Cycle Threshold Distribution in Clinical Specimens

Background

The detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patient samples is of critical importance in the management of patients and monitoring transmission in the population. However, data on the analytical performance characteristics for detection of SARS-CoV-2 in clinical specimens between individual targets within the same platform, and among different analytical platforms, are limited.

Methods

Here we evaluated the performance of 6 different sample-to-answer SARS-CoV-2 detection methods—Roche cobas 6800, Cepheid GeneXpert, Diasorin Simplexa, Luminex Aries emergency use authorization (EUA), Luminex Aries research use only (RUO), and bioMérieux BioFire—in clinical specimens with a range of viral loads.

Results

The positive percentage agreement between the Roche cobas 6800 and GeneXpert was 100%, Diasorin 95%, Aries EUA 74%, Aries RUO 83%, and BioFire 97%. Notably, in samples with cycle threshold (Ct) values below 30 for the E gene on the Roche cobas 6800 platform, we found 100% positive agreement among all platforms. Given these results, we examined the distribution of over 10 000 Ct values of all positive specimens from individuals at our institution on the Roche cobas platform. Nearly 60% of specimens from asymptomatic individuals had a PCR Ct value >30 as measured using the cobas 6800 assay E gene.

Conclusions

Our results demonstrate performance characteristics between different platforms by Ct value and provide data regarding the distribution of viral RNA present in positive specimens.

The Impact of Increasing Disease Prevalence, False Omissions, and Diagnostic Uncertainty on Coronavirus Disease 2019 (COVID-19) Test Performance

CONTEXT.—

Coronavirus disease 2019 (COVID-19) test performance depends on predictive values in settings of increasing disease prevalence. Geospatially distributed diagnostics with minimal uncertainty facilitate efficient point-of-need strategies.

OBJECTIVES.—

To use original mathematics to interpret COVID-19 test metrics; assess US Food and Drug Administration Emergency Use Authorizations and Health Canada targets; compare predictive values for multiplex, antigen, polymerase chain reaction kit, point-of-care antibody, and home tests; enhance test performance; and improve decision-making.

DESIGN.—

PubMed/newsprint-generated articles documenting prevalence. Mathematica and open access software helped perform recursive calculations, graph multivariate relationships, and visualize performance by comparing predictive value geometric mean-squared patterns.

RESULTS.—

Tiered sensitivity/specificity comprised: T1, 90%, 95%; T2, 95%, 97.5%; and T3, 100%, ≥99%. Tier 1 false negatives exceeded true negatives at >90.5% prevalence; false positives exceeded true positives at <5.3% prevalence. High-sensitivity/specificity tests reduced false negatives and false positives, yielding superior predictive values. Recursive testing improved predictive values. Visual logistics facilitated test comparisons. Antigen test quality fell off as prevalence increased. Multiplex severe acute respiratory syndrome (SARS)-CoV-2)*influenza A/B*respiratory syncytial virus testing performed reasonably well compared with tier 3. Tier 3 performance with a tier 2 confidence band lower limit will generate excellent performance and reliability.

CONCLUSIONS.—

The overriding principle is to select the best combined performance and reliability pattern for the prevalence bracket. Some public health professionals recommend repetitive testing to compensate for low sensitivity. More logically, improved COVID-19 assays with less uncertainty conserve resources. Multiplex differentiation of COVID-19 from influenza A/B-respiratory syncytial virus represents an effective strategy if seasonal flu surges next year.

The Hologic Aptima SARS-CoV-2 assay enables high ratio pooling saving reagents and improving turnaround time

BACKGROUND

The Hologic Aptima™ TMA SARS-CoV-2 assay was employed to test pooled nasopharyngeal (NP) samples to evaluate the performance of pooled sample testing and characterize variables influencing results.

METHODS

Results on 1033 previously tested NP samples were retrieved to characterize the relative light units (RLU) of SARS-CoV-2-positive samples in the tested population. The pooling strategy of combining 10 SARS-CoV-2 samples into one pool (10/1) was used in this study. The results were compared with neat sample testing using the same Aptima™ TMA SARS-CoV-2 assay and also the CDC RT-PCR and the Cepheid SARS-CoV-2 assays.

RESULTS

The Aptima assay compares favorably with both CDC RT-PCR and the Cepheid SARS-CoV-2 assays. Once samples are pooled 10 to 1 as in our experiments, the resulting signal strength of the assay suffers. A divide opens between pools assembled from strong-positive versus only weak-positive samples. Pools of the former can be reliably detected with positive percent agreement (PPA) of 95.2%, while pools of the latter are frequently misclassified as negative with PPA of 40%. When the weak-positive samples with kRLU value lower than 1012 constitute 3.4% of the total sample profile, the assay PPA approaches 93.4% suggesting that 10/1 pooled sample testing by the Aptima assay is an effective screening tool for SARS-CoV-2.

CONCLUSION

Performing pooled testing, one should monitor the weak positives with kRLU lower than 1012 or quantification cycle (Cq) value higher than 35 on an ongoing basis and adjust pooling approaches to avoid reporting false negatives.

ACoRE: Accurate SARS-CoV-2 genome reconstruction for the characterization of intra-host and inter-host viral diversity in clinical samples and for the evaluation of re-infections

Sequencing the SARS-CoV-2 genome from clinical samples can be challenging, especially in specimens with low viral titer. Here we report Accurate SARS-CoV-2 genome Reconstruction (ACoRE), an amplicon-based viral genome sequencing workflow for the complete and accurate reconstruction of SARS-CoV-2 sequences from clinical samples, including suboptimal ones that would usually be excluded even if unique and irreplaceable. The protocol was optimized to improve flexibility and the combination of technical replicates was established as the central strategy to achieve accurate analysis of low-titer/suboptimal samples. We demonstrated the utility of the approach by achieving complete genome reconstruction and the identification of false-positive variants in >170 clinical samples, thus avoiding the generation of inaccurate and/or incomplete sequences. Most importantly, ACoRE was crucial to identify the correct viral strain responsible of a relapse case, that would be otherwise mis-classified as a re-infection due to missing or incorrect variant identification by a standard workflow.

Evaluation of a High-Definition PCR Assay for the Detection of SARS-CoV-2 in Extracted and Nonextracted Respiratory Specimens Collected in Various Transport Media

Objectives

We conducted an analytic and clinical comparison of a novel high-definition polymerase chain reaction PCR (HDPCR) assay to traditional real-time PCR (RT-PCR) for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in upper respiratory specimens.

Methods

Analytic performance of RT-PCR, HDPCR, and extraction-free HDPCR was established through replicate testing of a serially diluted clinical specimen containing SARS-CoV-2. A clinical comparison of all 3 assays was conducted using 351 prospectively collected upper respiratory swab specimens obtained from symptomatic and asymptomatic individuals collected in various transport media.

Results

RT-PCR and HDPCR assays using extracted nucleic acid demonstrated similar analytic limits of detection (LoD) and clinical performance, with 100% positive and negative agreement. Extraction-free HDPCR demonstrated a 1.5 to 2.0 log₁₀ increase in LoD based on cycle threshold values. However, clinical performance of extraction-free HDPCR remained high, demonstrating 97.8% positive and 99.6% negative agreement with RT-PCR. An overall increase in “invalid” and “presumptive” results was observed when using the extraction-free method, but this was highly variable based on transport medium used.

Conclusions

HDPCR performs similar to RT-PCR for the detection of SARS-CoV-2. The use of an extraction-free HDPCR protocol maintained high clinical performance despite reduced analytic LoD, with the benefit of reduced hands-on time and cost of reagents associated with nucleic acid extraction.

Combination of rRT-PCR and Anti-Nucleocapsid/Anti-Spike Antibodies to Characterize Specimens with Very Low Viral SARs-CoV-2 Load: A Real-Life Experience

The objective of the present study was to evaluate the true positivity among people, whose results of initial testing of nasopharyngeal swabs (NPS) showed a very low viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Seventy-seven people detected with low viral loads of SARs-CoV-2 in nasopharyngeal samples (Ct ≥ 35) were enrolled in the study. For this purpose, a second NPS was collected for rRT-PCR (real-time reverse transcription polymerase chain reaction) combined with a pair of serum samples for detection of anti-nucleocapsid (anti-N) and anti-spike (anti-S) antibodies. In 8 people, subsequent examinations indicated an increase in viral loads, thereafter, followed by an increase of anti-N and anti-S antibodies, findings compatible with an early stage of COVID-19 infection. In 9 people, who already had increased anti-N antibodies, subsequent examination showed a decrease or absence of viral load and an increase in antibodies, indicative of a late stage of COVID-19 infection. In 60 people, subsequent examination showed absence of infection (as indicated by absence of viral load and antibodies). We propose that the combination of a second NPS and one serum-specimen, both taken three days after the first NPS, helps significantly to avoid false-positive results.

Aging correlates with lower threshold cycle values for RdRP/RdRP+S genes during molecular detection of SARS-CoV-2

RT-qPCR is the most reliable molecular method for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we analyzed results of RT-qPCR obtained for 3044 patients diagnosed as SARS-CoV-2-positive using four different molecular tests utilizing five RNA sequences. The analysis showed that patients' age inversely correlates with threshold cycle (Ct) values for RdRP gene (LightMix® Modular Wuhan CoV RdRP-gene by Roche Diagnostics) and RdRP+S genes (MutaPLEX® Coronavirus RT-PCR kit by Immundiagnostic). At the same time, there was no correlation between age and Ct values for E, N, and ORF1ab genes. When patients were grouped by age, mean Ct values for RdRP gene in older patients were significantly lower compared with younger individuals. Collectively, our report indicates that older SARS-CoV-2-infected individuals exhibit higher viremia at diagnosis than younger patients, which may reflect impaired functioning of their immune response and predispose to more severe disease and worse prognosis.

Increased complications in patients who test COVID-19 positive after elective surgery and implications for pre and postoperative screening

Background

The COVID-19 pandemic has necessitated the adoption of protocols to minimize risk of periprocedural complications associated with SARS-CoV-2 infection. This typically involves a preoperative symptom screen and nasal swab RT-PCR test for viral RNA. Asymptomatic patients with a negative COVID-19 test are cleared for surgery. However, little is known about the rate of postoperative COVID-19 positivity among elective surgical patients, risk factors for this group and rate of complications.

Methods

This prospective multicenter study included all patients undergoing elective surgery at 170 Veterans Health Administration (VA) hospitals across the United States. Patients were divided into groups based on first positive COVID-19 test within 30 days after surgery (COVID[-/+]), before surgery (COVID[+/−]) or negative throughout (COVID[−/−]). The cumulative incidence, risk factors for and complications of COVID[-/+], were estimated using univariate analysis, exact matching, and multivariable regression.

Results

Between March 1 and December 1, 2020 90,093 patients underwent elective surgery. Of these, 60,853 met inclusion criteria, of which 310 (0.5%) were in the COVID[-/+] group. Adjusted multivariable logistic regression identified female sex, end stage renal disease, chronic obstructive pulmonary disease, congestive heart failure, cancer, cirrhosis, and undergoing neurosurgical procedures as risk factors for being in the COVID[-/+] group. After matching on current procedural terminology code and month of procedure, multivariable Poisson regression estimated the complication rate ratio for the COVID[-/+] group vs. COVID[−/−] to be 8.4 (C.I. 4.9–14.4) for pulmonary complications, 3.0 (2.2, 4.1) for major complications, and 2.6 (1.9, 3.4) for any complication.

Discussion

Despite preoperative COVID-19 screening, there remains a risk of COVID infection within 30 days after elective surgery. This risk is increased for patients with a high comorbidity burden and those undergoing neurosurgical procedures. Higher intensity preoperative screening and closer postoperative monitoring is warranted in such patients because they have a significantly elevated risk of postoperative complications.

Modelling pooling strategies for SARS-CoV-2 testing in a university setting

Background: Pre-symptomatic and asymptomatic transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are important elements in the coronavirus disease 2019 (COVID-19) pandemic, and there remains a reliance on testing to manage the spread of the disease. In the UK, many universities opened for blended learning for the 2020-2021 academic year, with a mixture of face to face and online teaching. Methods: In this study we present a simulation framework to evaluate the effectiveness of different mass testing strategies within a university setting, across a range of transmission scenarios. Results: The sensitivity of 5x pooled RT-qPCR tests appears to be higher than testing using the lateral flow device with relatively little loss compared to single RT-qPCR tests, and is improved by pooling by social cluster. The range of strategies that we evaluated give comparable results for estimating prevalence. Conclusions: Pooling tests by known social structures, such as student households can substantially improve the cost effectiveness of RT-qPCR tests. We also note that routine recording of quantitative RT-qPCR results would facilitate future modelling studies.

Comparison and correlation of commercial SARS-CoV-2 real-time-PCR assays, Ireland, June 2020

We report the performance of a variety of commercially available SARS-CoV-2 PCR kits, used in several different sites across Ireland to determine if C_t values across platforms are comparable. We also investigate whether a C_t value, a surrogate for calculated viral loads in the absence of viral culture of > 34 can be used to exclude SARS-CoV-2 infection and its complications. We found a variation in C_t values from different assays for the same calculated viral load; this should be taken into consideration for result interpretation.

Effects of Storage Temperature and Media/Buffer for SARS-CoV-2 Nucleic Acid Detection

OBJECTIVES

The increase in the number of patients with coronavirus disease 2019 (COVID-19) has delayed real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR), requiring proper shipping and storage conditions, especially in hot weather. This study aims to assess how some conditions, such as storage period, temperature, media or buffer, and sample types, affect the results of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RT-qPCR.

METHODS

SARS-CoV-2-positive specimens were collected from Boramae Medical Center for 2 months (from May to June 2020) and stored in different media or buffers at different temperatures.

RESULTS

As a result of examining confirmed patient samples, RT-qPCR results were not significantly affected by 2°C to 8°C storage until after 7 days. When stored at 20°C to 22°C or above 35°C, the results were affected negatively even after 1 day. Higher storage temperatures resulted in a lower probability of detecting viral nucleic acids because of degradation. Samples stored in pH-controlled media or buffer were more stable than those stored in nonbuffer states.

CONCLUSIONS

These results emphasize the importance of storage temperature and media or buffer and performing RT-qPCR for SARS-CoV-2 nucleic acid detection as soon as possible after sample collection.

Saliva viral load is a dynamic unifying correlate of COVID-19 severity and mortality

While several clinical and immunological parameters correlate with disease severity and mortality in SARS-CoV-2 infection, work remains in identifying unifying correlates of coronavirus disease 2019 (COVID-19) that can be used to guide clinical practice. Here, we examine saliva and nasopharyngeal (NP) viral load over time and correlate them with patient demographics, and cellular and immune profiling. We found that saliva viral load was significantly higher in those with COVID-19 risk factors; that it correlated with increasing levels of disease severity and showed a superior ability over nasopharyngeal viral load as a predictor of mortality over time (AUC=0.90). A comprehensive analysis of immune factors and cell subsets revealed strong predictors of high and low saliva viral load, which were associated with increased disease severity or better overall outcomes, respectively. Saliva viral load was positively associated with many known COVID-19 inflammatory markers such as IL-6, IL-18, IL-10, and CXCL10, as well as type 1 immune response cytokines. Higher saliva viral loads strongly correlated with the progressive depletion of platelets, lymphocytes, and effector T cell subsets including circulating follicular CD4 T cells (cTfh). Anti-spike (S) and anti-receptor binding domain (RBD) IgG levels were negatively correlated with saliva viral load showing a strong temporal association that could help distinguish severity and mortality in COVID-19. Finally, patients with fatal COVID-19 exhibited higher viral loads, which correlated with the depletion of cTfh cells, and lower production of anti-RBD and anti-S IgG levels. Together these results demonstrated that viral load - as measured by saliva but not nasopharyngeal - is a dynamic unifying correlate of disease presentation, severity, and mortality over time.

A Rapid SARS-CoV-2 RT-PCR Assay for Low Resource Settings

Quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay is the gold standard recommended to test for acute SARS-CoV-2 infection. However, it generally requires expensive equipment such as RNA isolation instruments and real-time PCR thermal cyclers. As a pandemic, COVID-19 has spread indiscriminately, and many low resource settings and developing countries do not have the means for fast and accurate COVID-19 detection to control the outbreak. Additionally, long assay times, in part caused by slow sample preparation steps, have created a large backlog when testing patient samples suspected of COVID-19. With many PCR-based molecular assays including an extraction step, this can take a significant amount of time and labor, especially if the extraction is performed manually. Using COVID-19 clinical specimens, we have collected evidence that the RT-qPCR assay can feasibly be performed directly on patient sample material in virus transport medium (VTM) without an RNA extraction step, while still producing sensitive test results. If RNA extraction steps can be omitted without significantly affecting clinical sensitivity, the turn-around time of COVID-19 tests, and the backlog we currently experience can be reduced drastically. Furthermore, our data suggest that rapid RT-PCR can be implemented for sensitive and specific molecular diagnosis of COVID-19 in locations where sophisticated laboratory instruments are not available. Our USD 300 set up achieved rapid RT-PCR using thin-walled PCR tubes and a water bath setup using sous vide immersion heaters, a Raspberry Pi computer, and a single servo motor that can process up to 96 samples at a time. Using COVID-19 positive clinical specimens, we demonstrated that RT-PCR assays can be performed in as little as 12 min using untreated samples, heat-inactivated samples, or extracted RNA templates with our low-cost water bath setup. These findings can help rapid COVID-19 testing to become more accessible and attainable across the globe.