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Comparative Assessment of Maglumi Sars-Cov-2ag Test and Nucleic Acid Apmplification Test (Naat): First Considerations
Biochimica Clinica ; 46(3):S18-S19, 2022.
Article in English | EMBASE | ID: covidwho-2167992
ABSTRACT

Introduction:

NAAT is still the international reference assay for the diagnosis of Covid-19 due to high sensitivity and specificity;it is able to detect the pathogen even at low viral load, nevertheless a positive PCR result demonstrates the presence of nucleic acid in the sample, but not if it contains an infecting virus;the risk of unnecessarily isolate a person who is no longer infectious and a long TAT can preclude a screening utility. Conversely, immunoassays targeted to detect viral antigens have the potential to fit the requirements for a screening population test. In this study, we evaluated the consistency of results obtained by Maglumi SARS-CoV-2 Ag test in comparison with molecular test. Method(s) 79 positive NAAT nasopharyngeal swabs (NPS) with Ctthreshold cycle (Ct) between 39 and 13 were selected and analysed with MAGLUMI CLIA assay targeted to nucleocapsid SARS-Cov-2 antigen (M) by Snibe Diagnostic. 37 NPS were also analysed with Liaijson XL (L), DiaSorin s.p.a., which is routinary used in our lab. 5 negative NPS were included in the experiment as negative controls. Result(s) all 5 negative NPS were confirmed negative with both CLIA assays. 33 of 79 (41,8%) positive NPS were confirmed positive on M, all these samples had a Ct < 26. The remaining 46 positive NPS, resulting negative on M, had a Ct > 24. Results for 37 NPS tested both with M and L agreed 100%. Conclusion(s) CLIA test demonstrated to be less sensitive to the viral presence than NAAT, in particular M test seems to be able to detect a positivity to SARS-Cov-2 when the viral load is detected at a CT < 24. The grey area, where NAAT and CLIA were not in perfect agreement, seems to be Ct= 24 / 25. In this area M missclassified 67% of positive NPS, but further investigation with a larger number of samples is necessary to confirm this finding. While PCR positivity may persist for several weeks after the onset of the disease and the disappearance of symptoms, Ag tests reach satisfactory sensitivities when infected people are more likely to be contagious;together with the high throughput of the technology, makes them an extremely useful tool for screening population, especially during the pandemic.
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Collection: Databases of international organizations Database: EMBASE Language: English Journal: Biochimica Clinica Year: 2022 Document Type: Article

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Collection: Databases of international organizations Database: EMBASE Language: English Journal: Biochimica Clinica Year: 2022 Document Type: Article