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SARS-CoV-2 Rapid Antigen Test

SARS-CoV-2 rapid antigen test is an extremely valuable diagnostic point-of-care test with high specificity (99,68%). In general, those tests which detect antigens have lower sensitivity (96,52%) compared to molecular testing. Therefore, to make up for the potential decrease in sensitivity of an antigen test, negative results should be analysed in context of additional patient factors as previous exposure to COVID-19, clinical symptoms, additional test results to help guide the diagnosis and subsequent treatment of the patient. If the result is inconclusive, molecular testing can be performed within a couple of days.

The clinical impact of the rapid antigen testing largely depends on the circumstances in which they are used. The best result is obtained when the person is tested in the early stages of the SARS-CoV-2 infection when the viral load is generally the highest. Rapid tests are very informative for the persons who have been in contact with the confirmed COVID-19 cases and for the testing in high-risk environment (nursing homes and student dormitories) when repetitive testing can easily detect individuals with SARS-CoV-2 infection and prevent the spread of the infection.

HOW IS TESTING PERFORMED?

Testing is performed from the nasopharyngeal swab.

WHERE TO TEST?

Specialty Hospital St. Catherine Zagreb, Trpinjska 7, Zagreb.

PRELIMINARY ORDER MANDATORY!

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SARS-COV-2 RAPID ANTIGEN TESTING

New coronavirus SARS-CoV-2 belongs to the Coronaviridae family. N-antigen (Nucleocapside protein) is one of four SARS-CoV-2 structural proteins, and its function is to “pack” RNA viral genome inside the viral membrane to RNP (ribonucleoprotein) complex or capsid.


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SARS-CoV-2 N antigen concentration rapidly increases on the mucosa several days after infection, reaches a maximum around day 15, and in the next 10-15 days, decreases below the detection level.

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SARS-CoV-2 antigen test produced by Roche is a rapid chromatographic immunoassay (Figure 3) intended for the qualitative detection of the specific SARS-CoV-2 N antigen. Test is for use in healthcare setting from the nasopharyngeal or nasal swab and is intended for fast SARS-CoV-2 virus detection in symptomatic and in asymptomatic persons no matter of age. The test has a sensitivity of 96,52% (proportion of the infected persons accurately detected) and a specificity of 99,68% (proportion of the healthy persons accurately detected). Those results are confirmed by the analysis of 426 samples tested in two independent institutions.

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This test detects proteins, which are structural and functional parts of the virus called antigens. The antigen stands for all molecules that can cause an immune response in the body. If antigen SARS-CoV-2 is present in the sample in sufficient concentration, it will bind to specific antibodies resulting in a visible colored signal on the test device within 15 minutes. The result should be interpreted as a positive or negative.

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Point-of-care – specific location at which patient is presenting with illness - primary or secondary healthcare settings; TAT (Turnaround time) – the time interval between the specimen received in the laboratory to the time of report dispatched.

SARS-CoV-2 rapid antigen test is an extremely valuable diagnostic point-of-care test with high specificity (99,68%). In general, those tests which detect antigens have lower sensitivity (96,52%) compared to molecular testing (Table 1). Therefore, to make up for the potential decrease in sensitivity of an antigen test, negative results should be analysed in context of additional patient factors as previous exposure to COVID-19, clinical symptoms, additional test results to help guide the diagnosis and subsequent treatment of the patient. If the result is inconclusive, molecular testing can be performed within a couple of days.

The clinical impact of the rapid antigen testing largely depends on the circumstances in which they are used. The best result is obtained when the person is tested in the early stages of the SARS-CoV-2 infection when the viral load is generally the highest.
Rapid tests are very informative for the persons who have been in contact with the confirmed COVID-19 cases and for the testing in high-risk environment (nursing homes and student dormitories) when repetitive testing can easily detect individuals with SARS-CoV-2 infection and prevent the spread of the infection.

Literature:
1. Rapid Antigen Testing for SARS-CoV-2. URL: https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html Accessed 25/9/2020.
2. https://www.roche.com/media/releases/med-cor-2020-09-18b.html Accessed 25/9/2020.

Contact:
+385 1 2867 400
+385 1 2867 499
info@stcatherine.com

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