RE: Hold On To Your Hats8 Jan 2025 08:53
@stock ,
The recent diagnostics guidance from NICE (Diagnostic Guidance 59) recommended laboratory testing, where available, over a POCT approach in part because laboratory-based tests could theoretically test for a broader range of LoF alleles, and so would better serve ethnic minority groups who are more likely to carry these rarer variants. The Genedrive CYP2C19 ID Kit genotypes all of the CYP2C19 tier 1 variant alleles, as defined by the Association for Molecular Pathology, and several of the CYP2C19 tier 2 variant alleles.19 Those tier 2 alleles not tested (∗5, ∗6, ∗7, ∗9, and ∗10) represent a combined allele frequency of 0.1%–2.6%, depending on the biogeographical group. This represents relatively comprehensive coverage of currently known CYP2C19 variation and, by being able to test for the ∗35 allele that is present in 3.2% of sub-Saharan Africans and 1.6% of African Americans/Afro-Caribbeans, the Genedrive CYP2C19 ID Kit is therefore able to target a broader set of alleles than many laboratory-based platforms.
The assertion that, in theory, laboratory-based testing approaches allow a broader coverage of alleles is accurate. However, laboratory testing is heterogeneous and, in practice, most CYP2C19 testing approaches used in practice remain genotyping based and survey a small number of clinically relevant variants. More detailed sequencing-based approaches to include rarer, less well-evidenced, variants are available but come with several trade-offs. The cost, complexity, and turnaround time of these approaches would require considerable adaptation to existing clinical pathways, and there is significant uncertainty regarding whether they could be successfully implemented in the context of an acute presentation, such as ischemic stroke. These technologies may add value when used pre-emptively, where pharmacogenetic data are integrated into a patient's clinical record, but they are not easily conducive to a reactive implementation model. As part of their assessment, NICE found use of CYP2C19 genotyping to guide antiplatelet therapy was likely to be cost-effective via both laboratory and POCT approaches, including with the Genedrive CYP2C19 ID Kit.
The Genedrive CYP2C19 ID Kit compared favorably to the reference laboratory test in this assessment, and it has several advantages over the existing POCT on the market. The Genomadix Cube CYP2C19 POCT (Genomadix, Kanata, ON, Canada) has been extensively tested and is able to provide rapid and accurate CYP2C19 genotype data.20–22 However, as currently designed, the technology can only detect the ∗2, ∗3, and ∗17 alleles, has a higher reported price point, and, critically, requires cold reagent storage. In many acute clinical settings, freezer storage may not be available and, even if it is, having to consider this in the testing pathway introduces a cognitive burden and an implementation barrier.
https://www.jmdjournal.org/article/S1525-1578(24)00312-X/fulltext
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