AI Article Synopsis

  • Since late 2021, the Omicron variant and its sublineages (like BA.4 and BA.5) have been the dominant strains of SARS-CoV-2, and their detection via rapid antigen tests (RATs) is less effective compared to previous variants like Delta.
  • A study evaluated ten commonly used RATs on 171 respiratory samples from patients positive for Omicron-BA.4 and -BA.5, finding significant differences in test performance, with the worst RAT needing much higher viral loads to detect the infections.
  • The results showed that true-positive detection rates varied greatly depending on the viral load, highlighting the inconsistency in RAT effectiveness and raising concerns about their reliability for public use amidst the ongoing

Article Abstract

Since late 2021, the variant landscape of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been dominated by the variant of concern (VoC) Omicron and its sublineages. We and others have shown that the detection of Omicron-BA.1 and -BA.2-positive respiratory specimens by rapid antigen tests (RATs) is impaired compared to Delta VoC-containing samples. Here, in a single-center retrospective laboratory study, we evaluated the performance of ten most commonly used RATs for the detection of Omicron-BA.4 and -BA.5 infections. We used 171 respiratory swab specimens from SARS-CoV-2 RNA-positive patients, of which 71 were classified as BA.4 and 100 as BA.5. All swabs were collected between July and September 2022. 50 SARS-CoV-2 PCR-negative samples from healthy individuals, collected in October 2022, showed high specificity in 9 out of 10 RATs. When assessing analytical sensitivity using clinical specimens, the 50% limit of detection (LoD50) ranged from 7.6 × 10 to 3.3 × 10 RNA copies subjected to the RATs for BA.4 compared to 6.8 × 10 to 3.0 × 10 for BA.5. Overall, intra-assay differences for the detection of these two Omicron subvariants were not significant for both respiratory swabs and tissue culture-expanded virus isolates. In contrast, marked heterogeneity was observed among the ten RATs: to be positive in these point-of-care tests, up to 443-fold (BA.4) and up to 56-fold (BA.5) higher viral loads were required for the worst performing RAT compared to the best performing RAT. True-positive rates for Omicron-BA.4- or -BA.5-containing specimens in the highest viral load category (C values < 25) ranged from 94.3 to 34.3%, dropping to 25.6 to 0% for samples with intermediate C values (25-30). We conclude that the high heterogeneity in the performance of commonly used RATs remains a challenge for the general public to obtain reliable results in the evolving Omicron subvariant-driven pandemic.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10501931PMC
http://dx.doi.org/10.1007/s00430-023-00775-8DOI Listing

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