Anosmia Testing as Early Detection of SARS-CoV-2 Positivity; A Prospective Study under Screening Conditions.
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ABSTRACT:
SUBMITTER: Jungbauer F
PROVIDER: S-EPMC9319241 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:We conducted an extensive serological study to quantify population-level exposure and define correlates of immunity against SARS-CoV-2. We found that relative to mild COVID-19 cases, individuals with severe disease exhibited elevated authentic virus-neutralizing titers and antibody levels against nucleocapsid (N) and the receptor binding domain (RBD) and the S2 region of spike protein. Unlike disease severity, age and sex played lesser roles in serological responses. All cases, including asymptomatic individuals, seroconverted by 2 weeks post-PCR confirmation. RBD- and S2-specific and neutralizing antibody titers remained elevated and stable for at least 2-3 months post-onset, whereas those against N were more variable with rapid declines in many samples. Testing of 5882 self-recruited members of the local community demonstrated that 1.24% of individuals showed antibody reactivity to RBD. However, 18% (13/73) of these putative seropositive samples failed to neutralize authentic SARS-CoV-2 virus. Each of the neutralizing, but only 1 of the non-neutralizing samples, also displayed potent reactivity to S2. Thus, inclusion of multiple independent assays markedly improved the accuracy of antibody tests in low seroprevalence communities and revealed differences in antibody kinetics depending on the viral antigen. In contrast to other reports, we conclude that immunity is durable for at least several months after SARS-CoV-2 infection.
| S-EPMC7430613 | biostudies-literature
Project description:BACKGROUND:The capacity of the current molecular testing convention does not allow high-throughput and community level scans of COVID-19 infections. The diameter in the current paradigm of shallow tracing is unlikely to reach the silent clusters that might be as important as the symptomatic cases in the spread of the disease. Group testing is a feasible and promising approach when the resources are scarce and when a relatively low prevalence regime is observed on the population. METHODS:We employed group testing with a sparse random pooling scheme and conventional group test decoding algorithms both for exact and inexact recovery. RESULTS:Our simulations showed that significant reduction in per case test numbers (or expansion in total test numbers preserving the number of actual tests conducted) for very sparse prevalence regimes is available. Currently proposed COVID-19 group testing schemes offer a gain up to 15X-20X scale-up. There is a good probability that the required scale up to achieve massive scale testing might be greater in certain scenarios. We investigated if further improvement is available, especially in sparse prevalence occurrence where outbreaks are needed to be avoided by population scans. CONCLUSION:Our simulations show that sparse random pooling can provide improved efficiency gains compared to conventional group testing or Reed-Solomon error correcting codes. Therefore, we propose that special designs for different scenarios could be available and it is possible to scale up testing capabilities significantly.
| S-EPMC7330001 | biostudies-literature
Project description:Respiratory infections, like the current COVID-19 pandemic, target epithelial cells in the respiratory tract. Alveolar macrophages (AMs) are tissue-resident macrophages located within the lung. They play a key role in the early phases of an immune response to respiratory viruses. AMs are likely the first immune cells to encounter SARS-CoV-2 during an infection and their reaction to the virus will have a profound impact on the outcome of the infection. Interferons (IFNs) are antiviral cytokines and among the first cytokines produced upon viral infection. In this study, AMs from non-infectious donors are challenged with SARS-CoV-2. We demonstrate that challenged AMs are incapable of sensing SARS-CoV-2 and of producing an IFN response in contrast to other respiratory viruses, like influenza A virus and Sendai virus, which trigger a robust IFN response. The absence of IFN production in AMs upon challenge with SARS-CoV2 could explain the initial asymptotic phase observed during COVID-19 and argues against AMs being the sources of proinflammatory cytokines later during infection.
| S-SCDT-EMBOR-2020-51252V1 | biostudies-other
Project description:ObjectivesThe global spread of SARS-CoV-2 is a serious public health issue. Large-scale surveillance screenings are crucial but can exceed test capacities. We (A) optimized test conditions and (B) implemented pool testing of respiratory swabs into SARS-CoV-2 diagnostics.Study design(A) We determined the optimal pooling strategy and pool size. In addition, we measured the impact of vortexing prior to sample processing, compared a pipette-pooling method (by combining transport medium of several specimens) and a swab-pooling method (by combining several swabs into a test tube filled with PBS) as well as determined the sensitivities of three PCR assays. (B) Finally, we applied high-throughput pool testing for diagnostics.Results(A) In a low prevalence setting, we defined a preferable pool size of ten in a two-stage hierarchical pool testing strategy. Vortexing of swabs (n = 33) increased cellular yield by a factor of 2.34. By comparing Ct-values of 16 pools generated with two different pooling strategies, pipette-pooling was more efficient compared to swab-pooling. Measuring dilution series of 20 SARS-CoV-2 positive samples in three PCR assays simultaneously revealed detection rates of 85% (assay I), 50% (assay II), and 95% (assay III) at a 1:100 dilution. (B) We systematically pooled 55,690 samples in a period of 44 weeks resulting in a reduction of 47,369 PCR reactions.ConclusionsFor implementing pooling strategies into high-throughput diagnostics, we recommend utilizing a pipette-pooling method, performing sensitivity validation of the PCR assays used, and vortexing swabs prior to analyses. Pool testing for SARS-CoV-2 detection is feasible and effective in a low prevalence setting.
| S-EPMC8552800 | biostudies-literature
Project description:ImportanceLongitudinal mass testing using rapid antigen detection tests (RADT) for serial screening of asymptomatic persons has been proposed for preventing SARS-CoV-2 community transmission. The feasibility of this strategy relies on accurate self-testing.ObjectiveTo quantify the adequacy of serial self-performed SARS-CoV-2 RADT testing in the workplace, in terms of the frequency of correct execution of procedural steps and accurate interpretation of the range of possible RADT results.Design, setting, and participantsThis prospective repeated cross-sectional study was performed from July to October 2021 at businesses with at least 2 active cases of SARS-CoV-2 infection in Montreal, Canada. Participants included untrained persons in their workplace, not meeting Public Health quarantine criteria (ie, required quarantine for 10 days after a moderate-risk contact with someone infected with SARS-CoV-2). Interpretation and performance were compared between participants who received instructions provided by the manufacturer vs those who received modified instructions that were informed by the most frequent or most critical errors we observed. Data were analyzed from October to November 2021.ExposuresRADT testing using a modified quick reference guide compared with the original manufacturer's instructions.Main outcomes and measuresThe main outcome was the difference in correctly interpreted RADT results. Secondary outcomes included difference in proportions of correctly performed procedural steps. Additional analyses, assessed among participants with 2 self-testing visits, compared the second self-test visit with the first self-test visit using the same measures.ResultsOverall, 1892 tests were performed among 647 participants, of whom 278 participants (median [IQR] age, 43 [31-55] years; 156 [56.1%] men) had at least 1 self-testing visit. For self-test visit 1, significantly better accuracy in test interpretation was observed among participants using the modified quick reference guide than those using the manufacturer's instructions for reading results that were weak positive (64 of 115 participants [55.6%] vs 20 of 163 participants [12.3%]; difference, 43.3 [95% CI, 33.0-53.8] percentage points), positive (103 of 115 participants [89.6%] vs 84 of 163 participants [51.5%]; difference, 38.1 [95% CI, 28.5-47.5] percentage points), strong positive (219 of 229 participants [95.6%] vs 274 of 326 participants [84.0%]; difference, 11.6 [95% CI, 6.8-16.3] percentage points), and invalid (200 of 229 participants [87.3%] vs 252 of 326 participants [77.3%]; difference, 10.0 [95% CI, 3.8-16.3] percentage points). Use of the modified guide was associated with improvements on self-test visit 2 for results that were weak positive (difference, 15.4 [95% CI, 0.7-30.1] percentage points), positive (difference, 19.0 [95% CI, 7.2-30.9] percentage points), and invalid (difference, 8.0 [95% CI, 0.8-15.4] percentage points). For procedural steps identified as critical for test validity, adherence to procedural testing steps did not differ meaningfully according to instructions provided or reader experience.Conclusions and relevanceIn this cross-sectional study of self-performed SARS-CoV-2 RADT in an intended-use setting, a modified quick reference guide was associated with significantly improved accuracy in RADT interpretations.
| S-EPMC9077488 | biostudies-literature
Project description:IntroductionSymptoms associated with SARS-CoV-2 infection remain incompletely understood, especially among ambulatory, non-hospitalized individuals. With host factors, symptoms predictive of SARS-CoV-2 could be used to guide testing and intervention strategies.MethodsBetween March 16 and September 3, 2020, we examined the characteristics and symptoms reported by individuals presenting to a large outpatient testing program in the Southeastern US for nasopharyngeal SARS-CoV-2 RNA RT-PCR testing. Using self-reported symptoms, demographic characteristics, and exposure and travel histories, we identified the variables associated with testing positive using modified Poisson regression.ResultsAmong 20,177 tested individuals, the proportion positive was 9.4% (95% CI, 9.0-9.8) and was higher for men, younger individuals, and racial/ethnic minorities (all P<0.05); the positivity proportion was higher for Hispanics (26.9%; 95% CI. 24.9-29.0) compared to Blacks (8.6%; 95% CI, 7.6-9.7) or Whites (5.8%; 95% CI, 5.4-6.3). Individuals reporting contact with a COVID-19 case had the highest positivity proportion (22.8%; 95% CI, 21.5-24.1). Among the subset of 8,522 symptomatic adults who presented for testing after May 1, when complete symptom assessments were performed, SARS-CoV-2 RNA PCR was detected in 1,116 (13.1%). Of the reported symptoms, loss of taste or smell was most strongly associated with SARS-CoV-2 RNA detection with an adjusted risk ratio of 3.88 (95% CI, 3.46-4.35). The presence of chills, fever, cough, aches, headache, fatigue and nasal congestion also significantly increased the risk of detecting SARS-CoV-2 RNA, while diarrhea or nausea/vomiting, although not uncommon, were significantly more common in those with a negative test result. Symptom combinations were frequent with 67.9% experiencing ≥4 symptoms, including 19.8% with ≥8 symptoms; report of greater than three symptoms increased the risk of SARS-CoV-2 RNA detection.ConclusionsIn a large outpatient population in the Southeastern US, several symptoms, most notably loss of taste or smell, and greater symptom burden were associated with detection of SARS-CoV-2 RNA. Persons of color and those with who were a contact of a COVID-19 case were also more likely to test positive. These findings suggest that, given limited SARS-CoV-2 testing capacity, symptom presentation and host characteristics can be used to guide testing and intervention prioritization.
| S-EPMC8664207 | biostudies-literature
Project description:We study geographical epidemic scales and patterns and positivity trends of SARS-CoV-2 pandemics in mass antigen testing in Slovakia in 2020. The observed test positivity was exponentially distributed with a long scale exponential spatial trend, and its characteristic correlation length was approximately 10 km. Spatial scales also play an important role in test positivity reduction between two consecutive testing rounds. While test positivity decreased in all counties, it increased in individual municipalities with low test positivity in the earlier testing round in a way statistically different from a mean-reversion process. Also, non-residents testing influences the mass testing results as test positivity of non-residents was higher than of residents when testing was offered only in municipalities with the highest positivity in previous rounds. Our results provide direct guidance for pandemic geographical data surveillance and epidemic response management.
| S-EPMC8386854 | biostudies-literature
Project description:ObjectivesWe aimed to identify populations at a high risk for SARS-CoV-2 infection but who are less likely to present for testing, by determining which sociodemographic and household factors are associated with a lower propensity to be tested and, if tested, with a higher risk of a positive test result.Design and settingInternet-based participatory surveillance data from the general population of the Netherlands.ParticipantsWeekly survey data collected over a 5-month period (17 November 2020 to 18 April 2021) from a total of 12 026 participants who had contributed at least 2 weekly surveys was analysed.MethodsMultivariable analyses using generalised estimating equations for binomial outcomes were conducted to estimate the adjusted ORs of testing and of test positivity associated with participant and household characteristics.ResultsMale sex (adjusted OR for testing (ORt): 0.92; adjusted OR for positivity (ORp): 1.30, age groups<20 (ORt: 0.89; ORp: 1.27), 50-64 years (ORt: 0.94; ORp: 1.06) and 65+ years (ORt: 0.78; ORp: 1.24), diabetics (ORt: 0.97; ORp: 1.06) and sales/administrative employees (ORt: 0.93; ORp: 1.90) were distinguished as lower test propensity/higher test positivity factors.ConclusionsThe factors identified using this approach can help identify potential target groups for improving communication and encouraging testing among those with symptoms, and thus increase the effectiveness of testing, which is essential for the response to the COVID-19 pandemic and for public health strategies in the longer term.
| S-EPMC8692782 | biostudies-literature
Project description:Repeated positivity and reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) is a significant concern. Our study aimed to evaluate the clinical significance of repeatedly positive testing after coronavirus disease 2019 (COVID-19) recovery. We performed a systematic literature search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. With available individual patient data reporting on repeatedly SARS-CoV-2 positive (RSP) patients, case reports, and case series were included in this analysis. We performed a descriptive analysis of baseline characteristics of repeatedly positive cases. We assessed the cases according to the length of their polymerase chain reaction (PCR) negative interval between the two episodes. Risk factors for the severity of second episodes were evaluated. Overall, we included 123 patients with repeated positivity from 56 publications, with a mean repeated positivity length of 47.8 ± 29.9 days. Younger patients were predominant in the delayed (>90 days) recurrent positive group. Furthermore, comparing patients with RSP intervals of below 60 and above 60 days, we found that a more severe disease course can be expected if the repeated positivity interval is shorter. Severe and critical disease courses might predict future repeatedly positive severe and critical COVID-19 episodes. In conclusion, our results show that the second episode of SARS-CoV-2 positivity is more severe if it happens within 60 days after the first positive PCR. On the other hand, the second episode's severity correlates with the first.
| S-EPMC8003803 | biostudies-literature
Project description:Enhanced community surveillance is a key pillar of the public health response to coronavirus disease 2019 (COVID-19). Asymptomatic carriage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a potentially significant source of transmission, yet remains relatively poorly understood. Disruption of dental services continues with significantly reduced capacity. Ongoing precautions include preappointment and/or at appointment COVID-19 symptom screening and use of enhanced personal protective equipment (PPE). This study aimed to investigate SARS-CoV-2 infection in dental patients to inform community surveillance and improve understanding of risks in the dental setting. Thirty-one dental care centers across Scotland invited asymptomatic-screened patients aged over 5 y to participate. Following verbal consent and completion of sociodemographic and symptom history questionnaire, trained dental teams took a combined oropharyngeal and nasal swab sample using standardized Viral Transport Medium-containing test kits. Samples were processed by the Lighthouse Lab and patients informed of their results by SMS/email with appropriate self-isolation guidance in the event of a positive test. All positive cases were successfully followed up by the national contact tracing program. Over a 13-wk period (from August 3, 2020, to October 31, 2020), 4,032 patients, largely representative of the population, were tested. Of these, 22 (0.5%; 95% CI, 0.5%-0.8%) tested positive for SARS-CoV-2. The positivity rate increased over the period, commensurate with uptick in community prevalence identified across all national testing monitoring data streams. To our knowledge, this is the first report of a COVID-19 testing survey in asymptomatic-screened patients presenting in a dental setting. The positivity rate in this patient group reflects the underlying prevalence in community at the time. These data are a salient reminder, particularly when community infection levels are rising, of the importance of appropriate ongoing infection prevention control and PPE vigilance, which is relevant as health care team fatigue increases as the pandemic continues. Dental settings are a valuable location for public health surveillance.
| S-EPMC8138329 | biostudies-literature