engleski

Evaluation of SARS-CoV-2 rapid diagnostic antigen test in COVID-19 suspected patients in Croatia

Background The gold standard for COVID-19 diagnosis is reverse transcription-polymerase chain reaction (RT-PCR) test. The fast spreading of SARS-COV-2 contributed to the need for using tests with quicker results. Rapid antigen detection tests (Ag-RDT) differ in their specificity and sensitivity, which should be as close as possible to the gold standard. Methods During November and December 2020, nasopharyngeal swabs (NPS) were obtained from COVID-19 suspected patients at the University Hospital for Infectious Diseases, Zagreb, Croatia, and tested immediately on-site with Ag-RDT for SARS-CoV-2 (SARS-CoV-2 Rapid Antigen Test Roche/SD Biosensor, Germany/Korea) following manufacturer's instructions. In case of negative Ag-RDT, a new NPS was tested for viral RNA with RT-PCR Roche cobas® SARS-CoV-2 Test (Mannheim, Germany). Diagnostic accuracy of Ag-RDT was determined in comparison to the RT-PCR. The results were evaluated according to the time of symptom onset, patient age and gender. Results Out of 1317 patients (mean age 50.47 years (SD 21.15) ; males 52.01%), 788 (66.94%) were confirmed for COVID-19. Within the first seven days and from day eight after symptom onset, SARS- CoV-2 Ag-RDT was positive in 555 (49.73%) and 96 (47.76%) patients, respectively. False-negative Ag-RDT and RT-PCR positive findings were found in 84 (7.53%) patients within the first seven days, and in 55 (27.36%) from day eight after symptom onset. Overall sensitivity and specificity of Ag- RDT was 82.36% (95%CI 80.42-85.01) and 99.49% (95%CI 98.32- 100%), respectively, with Cohen’s Kappa 0.75 (95% CI 0.71-0.79). Test sensitivity for patients with NPS collected within the first seven days of illness and from day eight after symptom onset was 86.81% (95% CI 84.05-89.00) and 63.58% (95%CI 55.54-71.14), with Cohen’s Kappa 0.82 (95% CI 0.79-0.86) and 0.39 (95% CI 0.28- 0.49), respectively. Tests done eight or more days after symptom onset were found to have a significantly higher odds of falsenegative results (OR 3.76 ; 95%CI 2.46-5.74, p=0.0). Conclusions SARS- COV-2 Ag-RDT showed good agreement with RT-PCR, especially in the first week after symptom onset. The accuracy of Ag-RDT depends on the collection sample time after symptom onset. In case of Ag-RDT negative result, RT-PCR test is obligatory. Furthermore, in the late stage of disease, serology is recommended.

SARS-CoV-2 rapid antigen test ; COVID-19 patients ; diagnostic accuracy

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