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Tag: testing
April 29, 2021
Temporal Dynamics of Viral Load and False Negative Rate Influence the Levels of Testing Necessary to Combat COVID-19 Spread
A SARS-CoV-2 transmission model calibrated to a university population with 50% asymptomatic infections suggests that temporal viral load dynamics, which account for viral loads below detectable levels prior to symptom onset, could result in false negative rates of 17-48%. The authors suggest that models that do not account for the effect of this undetectable period…
Complications of COVID-19 Nasopharyngeal Swab Test
Complications requiring emergency department treatment from nasopharyngeal swab sampling for SARS-CoV-2 PCR tests occurred in 1.24 per 100,000 tests during a 7-month period in Helsinki University Hospital, Finland. Out of over 640,000 PCR tests performed, 8 complication-related visits were identified in patients presenting to the emergency department (4 nasal bleeds, of which half were potentially…
A Comparison of Less Invasive SARS-CoV-2 Diagnostic Specimens in Nursing Home Residents — Arkansas, June–August 2020
In a comparison study of longitudinally collected samples for SARS-CoV-2 PCR testing among nursing home residents within 15 days of their first positive SARS-CoV-2 RT-PCRS result (n=17), saliva swabs (SA) and oropharyngeal swabs (OR) were PCR-positive for up to 48 days. Anterior nasal swabs (AN) were only positive for up to 33 days, but had…
April 28, 2021
The Dark Side of SARS-CoV-2 Rapid Antigen Testing Screening Asymptomatic Patients
[Pre-print, not peer-reviewed] A SARS-CoV-2 rapid antigen test (Standard Q) only identified 2 of 7 PCR positive patients when used as a screening tool before hospital admission for asymptomatic patients (n=116) in Switzerland, corresponding to a sensitivity of 29%. The rapid test also delivered two false positives (specificity=98.2%). Nasopharyngeal swabs for both the rapid test…
Implementation of Rapid and Frequent SARS-CoV2 Antigen Testing and Response in Congregate Homeless Shelters
[Pre-print, not peer-reviewed] A pilot program offering SARS-CoV-2 rapid antigen tests (BinaxNOW) identified three outbreaks among staff and residents of 10 participating homeless shelters in San Francisco over a period of one month. Roughly half of 828 residents and 435 staff participated per testing event, with 2.2% of participants testing positive. The implementation science analysis…
April 27, 2021
SARS-Cov2 Infection Detection by Polymerase Chain Reaction and Serologic Testing in Clinical Practice
A retrospective study found that 7% participants (271 of 3,075) who underwent both PCR and serologic testing had discordant test results (i.e. negative PCR result and seropositive or vice-versa). These participants either sought PCR testing after viral shedding would be expected to have ended (PCR- but seropositive) or sought serology tests before a detectable antibody…
SARS-CoV-2 in Nursing Homes after 3 Months of Serial, Facilitywide Point Prevalence Testing, Connecticut, USA
The implementation of point prevalence survey (PPS) testing for SARS-CoV-2 infections in 34 nursing homes in Connecticut was associated with a 41-80% reduction in the incidence rate in nursing homes. Data were obtained from public health surveillance records beginning 4 weeks prior to widespread implementation of PPS testing on May 2020 and up to 12…
April 22, 2021
Airport Traveler Testing Program for SARS-CoV-2 — Alaska, June–November 2020
0.8% of passengers arriving to Alaska from June to November 14, 2020 tested positive for SARS-CoV-2 (951 of 126,000 tests). Passengers tested on arrival made up roughly a third of all air travelers arriving in Alaska during the study period, as other travelers opted to be tested within 72 hours before arrival or to self-quarantine…
An International, Interlaboratory Ring Trial Confirms the Feasibility of an Open-Source, Extraction-Less “Direct” RT-QPCR Method for Reliable Detection of SARS-CoV-2 RNA in Clinical Samples
[Pre-print, not peer-reviewed] An international interlaboratory trial observed 100% concordance in using “direct” RT-PCR across the 10 included laboratories (3 in US, including the University of Washington Virology Lab [UWVL]). “Direct” or “extraction-less” RT-PCR is an inexpensive alternative to conventional RT-qPCR that does not require a resource intensive RNA extraction step. The assay was found…
April 19, 2021
Clinical Characteristics of False Negative SARS-CoV-2 Test Results Amongst Hospitalized Patients
False negative SARS-CoV-2 RT-PCR results, defined as an initial negative test followed by a positive test within seven days, were associated with loss of taste or smell (aOR = 8.4), having a SARS-CoV-2-positive contact (aOR = 10.5), and having an elevated lactate dehydrogenase level (aOR = 3.3) compared to true negative results. Among 1,009 SARS-CoV-2 test…
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