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We evaluated the diagnostic performance of the STANDARD i-Q COVID-19 Ag Test, which was developed to detect viral antigens, using nasal and oral swabs. Sixty positive and 100 negative samples were analyzed. We determined the distribution of the Ct values according to the day of sample collection after symptom onset, the diagnostic performance of the total samples and subgroups separated by Ct value or time of sample collection, and the Ct value at which maximal accuracy was expected. No differences were observed in Ct values, except for the samples obtained on the day of symptom onset. The diagnostic sensitivity and specificity of the oral swabs were 75.0 and 100.0%, respectively, whereas those of the nasal swabs were 85.0 and 98.0%, respectively. The sensitivity was higher in samples with a high viral load collected earlier than those collected later, although the difference was not significant. False-negative results were confirmed in all samples with a Ct value ≥ 30.0. These results indicate that tests using oral and nasal swabs are helpful for diagnosing acute symptomatic cases with suspected high viral loads. Our tests exhibited relatively low sensitivity but high specificity rates, indicating the need to assess negative antigen test results. [ABSTRACT FROM AUTHOR]

Background: During the last two years, a variety of assays for the serological detection of antibodies to the new SARS-CoV-2 virus have been launched and used as part of standard care in many laboratories. The pace with which these tests have been introduced into routine care emphasizes the importance of quality measures for analytical methods, particularly with regard to the implications of results for clinical and epidemiologic decisions. Accuracy, reliability and comparability of analytical test results are thus essential, and here external quality assessment (EQA) is the most important quality assurance tool. It allows us to achieve harmonization of test methods as a prerequisite for a high standard of performance for laboratory and analytical techniques and their interpretation. Methods: This EQA scheme consisted of pre-characterized clinical biospecimens dedicated to the analysis of anti-SARS-CoV-2 IgG total antibodies and differentiation into spike protein-specific IgG antibodies against SARS-CoV-2 (anti-S-SARS-CoV-2) and nucleocapsid-specific IgG antibodies against SARS-CoV-2 (anti-N-SARS-CoV-2). Results: A total of 239 laboratories across Europe participated in this scheme, called CoVimm. In detail, 536 results for anti-SARS-CoV-2 IgG, 431 results for anti-S-SARS-CoV-2 IgG, and 200 results for anti-N-SARS-CoV-2 IgG were reported. Based on the pre-defined thresholds, the success rates for the determination of anti-S-SARS-CoV-2 IgG and anti-N-SARS-CoV-2 IgG were 96% and 90%, respectively. Interestingly, only 64% of the participating laboratories successfully passed the EQA scheme for the determination of total anti-SARS-CoV-2 IgG. Conclusions: This EQA revealed serious concerns regarding the reliability and appropriate use of anti-SARS-CoV-2 antibody assays in routine care. In addition to the wide heterogeneity of different assays used by participating laboratories, a lack of standardization and harmonization is also evident. This is of particular importance for reliable and clinically meaningful interpretation of test results. [ABSTRACT FROM AUTHOR]

(1) Background: Laboratory-based molecular assays are the gold standard to detect SARS-CoV-2. In resource-limited settings, the implementation of these assays has been hampered by operational challenges and long turnaround times. Rapid antigen detection tests are an attractive alternative. Our aim is to evaluate the clinical performance of two SARS-CoV-2 rapid antigen tests during a high transmission period. (2) Methods: A total of 1277 patients seeking SARS-CoV-2 diagnosis were enrolled at four health facilities. Nasopharyngeal swabs for rapid antigen and real time PCR testing were collected for each patient. Sensitivity, specificity, positive and negative predictive values, misclassification rate, and agreement were determined. (3) Results: The overall sensitivity of Panbio COVID-19 was 41.3% (95% CI: 34.6–48.4%) and the specificity was 98.2% (95% CI: 96.2–99.3%). The Standard Q had an overall sensitivity and specificity of 45.0% (95% CI: 39.9–50.2%) and 97.6% (95% CI: 95.3–99.0%), respectively. The positive predictive value of a positive test was 93.3% and 95.4% for the Panbio and Standard Q Ag-RDTs, respectively. A higher sensitivity of 43.2% and 49.4% was observed in symptomatic cases for the Panbio and Standard Q Ag-RDTs, respectively. (4) Conclusions: Despite the overall low sensitivity, the two evaluated rapid tests are useful to improve the diagnosis of symptomatic SARS-CoV-2 infections during high transmission periods. [ABSTRACT FROM AUTHOR]