The availability of accurate and rapid diagnostic tools to determine the presence of SARS-CoV-2 is essential to address the current pandemic. Reverse transcription polymerase chain reaction (rRT-PCR) is considered the gold standard for diagnosing SARS-CoV-2 virus, but the lack of reagent supply and the time delay of the test, which limits the number of daily tests, have prompted the development of rapid diagnostic tests, which rely on the detection of viral antigens. The purpose of this master's thesis is to compare Quidel's rapid test Sofia SARS antigen FIA® (Sofia) with the rRT-PCR test. For the purpose of comparison, two swabs were taken from the test subjects, the first for testing with the Sofia test and the second for testing with the rRT-PCR test. In total, swabs were taken from 146 patients brought and hospitalized in the gray zone of the Clinic for Infectious Diseases and Febrile Conditions of the University Medical Center Ljubljana and 672 patients brought to the Internal Medicine First Aid Department of the University Medical Center who were tested regardless of covid-19 symptoms.
In group 1, a group of symptomatic test subjects, the sensitivity of the antigen test was 90.0% and the specificity was 97.5%. In group 2, a group of both symptomatic and asymptomatic test subjects, the sensitivity of the antigen test was 81.4% and the specificity of 98.9%. From our data we concluded that the Sofia test is diagnostically comparable to the rRT-PCR test in the case of symptomatic patients and slightly less reliable in the case of testing asymptomatic patients. This was confirmed by McNemar's statistical test. The value of p was 0.625 in the case of symptomatic test subjects, and the value of p was less than 0.001 in the case of both symptomatic and asymptomatic test subjects. In addition to asymptomatic patients, false negative results of rapid antigen tests also occurred in subjects with high cycle thresholdvalues Ct> 30). Nevertheless, our results show that the Sofia test meets the criteria of the diagnostic test, according to the criteria of the World Health Organization, as it shows high sensitivity and specificity and perhaps most importantly a high negative predictive value (> 95%).
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