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Objective The purpose of this study was to compare Quidel’s rapid antigen test Sofia SARS antigen Fluorescent Immunoassay (FIA) (Sofia) with the real-time reverse transcription–polymerase chain reaction (rRT-PCR) test. Methods Two samples were taken from each test subject—1 for testing with the Sofia test and 1 for testing with the rRT-PCR test. In total, swabs were taken from 146 subjects who presented symptoms of infection (group 1) and 672 subjects who were tested regardless of symptoms (group 2). Results In group 1, the sensitivity of the antigen test was 90.0% and its specificity 97.5%. In group 2, however, the sensitivity of the antigen test was 81.4% and the specificity 98.9%. In addition to asymptomatic patients, false-negative results of rapid antigen tests also occurred in subjects with high threshold values (cycle threshold > 30). Conclusion Our results show that the Sofia test meets the standards for diagnostic tests according to the criteria of the World Health Organization, as they show high sensitivity and specificity, and perhaps most importantly, a high negative predictive value (> 95%).

Razpoložljivost natančnih in hitrih diagnostičnih orodij za določanje prisotnosti SARS-CoV-2 je bistvenega pomena za spopadanje s trenutno pandemijo. Obratna transkripcija in verižna reakcija s polimerazo v realnem času (rRT-PCR) velja za zlati standard diagnostike virusa SARS-CoV-2. Pomanjkanje oskrbe z reagenti in časovna zamudnost testa, omejujeta število dnevno izvedenih testov, kar je spodbudilo razvoj hitrih diagnostičnih testov, ki slonijo na zaznavanju virusnih antigenov. Namen te magistrske naloge je primerjava Quidelovega hitrega testa Sofia SARS antigen FIA® (Sofia) s testom rRT-PCR. Za namen primerjave smo testirancem odvzeli dva brisa, prvega za testiranje s testom Sofia in drugega za testiranje s testom rRT-PCR. V celoti smo brise odvzeli 146 pacientom, pripeljanim in hospitaliziranim v sivi coni Klinike za infekcijske bolezni in vročinska stanja UKC Ljubljana in 672 pacientom pripeljanim na oddelek Internistične prve pomoči UKC, ki so bili testirani ne glede na to ali so izkazovali simptome covid-19. V skupini 1, skupini simptomatskih testirancev, je bila občutljivost antigenskega testa 90,0 % in specifičnost 97,5 %. V skupini 2, skupini tako simptomatskih kot asimptomatskih testirancev, pa je bila občutljivost antigenskega testa 81,4 % in specifičnost 98,9 %. Iz naših podatkov smo zaključili, da je test Sofia diagnostično primerljiv testu rRT-PCR v primeru testiranja simptomatskih pacientov in nekoliko manj zanesljiv v primeru testiranja asimptomatskih pacientov. To smo potrdili z McNemarjevim statističnim testom. Vrednost p je bila v primeru simptomatskih testirancev 0,625, v primeru tako simptomatskih kot asimptomatskih testirancev pa je bila vrednost p manjša od 0,001. Lažno negativni rezultati hitrih antigenskih testov so se poleg asimptomatskih pacientov pojavljali tudi pri testirancih z visokimi pražnimi vrednostmi (Ct >30). Kljub temu pa naši rezultati kažejo, da test Sofia ustreza kriterijem diagnostičnega testa po kriterijih Svetovne zdravstvene organizacije, saj izkazujejo visoko občutljivost in specifičnost ter morda najpomembneje, visoko negativno napovedno vrednost( > 95 %). 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%).