RESUMO
BACKGROUND: The global outbreak of coronavirus disease 2019 (COVID-19) leads to the development of accessible and cost-effective rapid antigen-detection tests (RATs), as quick and accurate diagnosis is crucial to curb the pandemic. AIM: To evaluate the Humasis COVID-19 Ag Test (Humasis Co., Ltd., Gyeonggi-do, Republic of Korea) in the diagnosis of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). METHODS: This retrospective study was carried out at the Croatian Institute of Public Health and included patients with clinical symptoms of COVID-19 lasting no longer than 5 d prior to testing, whose nasopharyngeal swabs were primarily tested with RAT. Negative RAT samples underwent confirmatory real-time reverse transcription-polymerase chain reaction (RT-PCR). Diagnostic efficacy was determined compared to RT-PCR. The patients were divided into three age groups (< 18, 19-65, > 65 years). Statistical analysis was performed with the significance level set at P < 0.05. RESULTS: In total, 2490 symptomatic patients were tested; 953 samples were positive on RAT, and 1537 were negative. All negative RAT samples were subjected to RT-PCR; 266 samples were positive and marked as false-negative results on RAT. The calculated negative predictive value as a measure of RAT efficacy was 82.69%. The χ 2 test and Kruskal-Wallis test showed a significant difference in the proportion of false negatives (P < 0.001) and RT-PCR cycle (Ct) values for false-negative RATs (P = 0.012) among the age groups. The young age group was significantly less likely to be false negative, whereas the false negatives from the elderly group experienced significantly lower Ct values than the other two age groups. CONCLUSION: Evaluated RAT demonstrated satisfactory performance with more reliable results in younger patients. Humasis COVID-19 Ag RAT is potentially a valuable tool in areas where access to molecular methods is limited; however, RT-PCR remains a gold standard for SARS-CoV-2 detection.
RESUMO
BACKGROUND: Due to rapid spread, the Omicron variant has become the dominant SARS-CoV-2 variant responsible for infections worldwide. We present the first detection of the Omicron variant in Croatia which resulted in rapid cross-border spreading. METHODS: Whole-genome sequencing was performed using the Illumina MiniSeq sequencing system. SARS-CoV-2 lineages were identified using the PANGOLIN and GISAID databases. RESULTS: The first case of the Omicron variant (BA.1.17) emerged in Croatia after a workshop held in Zagreb in November 2021. The patient reported a history of previous COVID-19 and received two doses of an mRNA vaccine. Three additional cases were detected among Croatian participants of the workshop. At the beginning of December, SARS-CoV-2 infection was confirmed in one participant from Montenegro and her husband. Phylogenetic analysis showed that the detected Omicron variants were closely related to the first Croatian case, confirming the connection with the workshop outbreak and rapid cross-border spreading. Subsequent analyses of SARS-CoV-2 positive samples in Croatia showed the rapid introduction of the Omicron variant and depletion of the Delta variant resulting in the fifth pandemic wave. CONCLUSIONS: Genomic monitoring and early detection of novel SARS-CoV-2 variants are essential to implement timely epidemiological interventions and reduce further transmission in the population.
