12/9/2023 0 Comments Sample negative covid test resultsSystemic delays in the booking of patients for testing unnecessarily increases the number of false-negative results, and can be addressed by returning to a decentralized process that reintroduces family medicine clinics as testing sites for moderately ill cases ( Figure 1). ![]() 12 Testing someone before symptom onset or more than 10 days after symptom onset risks a higher likelihood of false-negative results. ![]() 9- 11 Although there is limited published information on the testing period with the lowest number of false-negative results, Kucirka and colleagues have modeled that the best testing period from the onset of any symptoms is within the first 7 to 10 days. The only factor that can be substantially improved at the population level is to reduce the time between the onset of illness and high-quality oropharyngeal (or nasopharyngeal) testing, so as to ensure that sampling occurs during the optimal time for detecting the virus in the upper respiratory tract. 8 Until there is improvement in the supply of nasopharyngeal swabs within Canada, this factor cannot be addressed. Owing to a global shortage of nasopharyngeal swabs, Canadian jurisdictions have been forced to use the alternative swabbing techniques. 7 Deep nasal swabbing was quickly abandoned by Alberta Health Services following a preliminary study 6 showing it to be less reliable, especially when used by nonphysicians at large drive-through assessment centres. 6 Canadian family physicians have a long history of competently conducting nasopharyngeal testing during the annual influenza season, including formal participation in the FluWatch Sentinel Practitioner ILI Surveillance Program. While nasopharyngeal swabbing requires trust between the provider and the patient to perform, the swab is unlikely to miss sampling the infected mucosa, compared with either a deep nasal or an oropharyngeal (throat) swab. ![]() Those patients with severe acute COVID-19 will be hospitalized and tested immediately however, testing in the community is another story. Thus, the timing and technique of sampling during clinical encounters could potentially be the factors most amenable to improvement. 5 Moreover, the local-provincial-federal system of specimen collection and transport to centralized laboratory sites has been reliable during several decades in its testing for other infectious diseases. 2 So why are the tests not identifying more of these cases?ĬOVID-19-coronavirus disease 2019, RT-PCR-reverse transcriptase–polymerase chain reaction.Īlthough jurisdictions in other countries have cited varying false-negative rates, some as high as 50%, 4 provincial systems, such as Alberta’s laboratory testing process, have yielded 100% accuracy, as confirmatory testing by Canada’s National Microbiology Laboratory has shown. While the surge of cases in the province (most occurring in Calgary) reached an apex on April 23, 2020, steady daily cases have continued to be reported since May 3, 2020, which suggests ongoing undetected community spread. 1 And yet, despite its having one of the highest per capita testing rates in North America, Alberta had only 7044 confirmed cases of COVID-19 (or a positive rate of 3%), which included those cases that entered from outside the country at the start of the pandemic. As of June 1, 2020, 263 074 tests had been conducted on 237 747 persons in Alberta. However, current COVID-19 results from nasopharyngeal and oropharyngeal swabbing suggest that, overall, the testing procedures used in Canada need improvement. ![]() During this vulnerable period, reliable and valid testing of acute cases will remain an important means to control community spread. During the coming year or two, it is likely that the vaccines and antiviral drugs needed to combat this pandemic will still be going through development, testing, and production, and will not yet be ready for full implementation. As Canada has moved out of full public health lock-down to restart the economy, we know that flares of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections causing coronavirus disease 2019 (COVID-19) will need to be promptly detected to mitigate the second and third outbreak waves in the coming months.
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