Resolving conflicting LDLR variants in ClinVar - Progress of the ClinGen familial hypercholesterolemia variant curation expert panel

Chora, J.; Iacocca, M.; Elnagheeb, M.; Kullo, I.; Bourbon, M.; on behalf of the ClinGen FH VCEP

http://hdl.handle.net/10400.18/8965

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on behalf of the ClinGen FH VCEP

Abstract(s)

Familial hypercholesterolemia (FH) is the most common monogenic disorder of lipid metabolism. Genetic testing can confirm the clinical diagnosis, but there are currently over 3300 different variants in LDLR deposited in ClinVar and ~400 had conflicting classifications of pathogenicity. Here, we present the progress of LDLR variant classification by the FH Variant Curation Expert Panel (VCEP), composed of 13 reviewers, 17 curators, and 12 associated labs, with our LDLR consensus variant classification guidelines. Variants with conflicting classifications and other variants in the same codon (required to properly classify conflicting variants) are prioritized. Associated labs send internal variant case-level data, which is uploaded into the Variant Curation Interface (VCI) and supplemented by literature evidence. Each variant is assessed by one (very experienced) or two curators and approved by three reviewers before being officially published to ClinVar. As of December 2022, we have completed classification of 316 LDLR variants. Of those with prior conflicting classifications (n=165), 33% were classified as Pathogenic/Likely pathogenic (P/LP), 9% as Benign/Likely benign (B/LB), 55% as Variant of Uncertain Significance (VUS) by insufficient evidence and only 3% remained conflicting. Of the remaining 135 variants, 53% were classified as P/LP, 2% as B/LB and 45% as VUS. Until May 2023, we will evaluate 451 LDLR variants, 247 of them with prior conflicting classifications. Ultimately, efforts of the FH VCEP are aimed at improving FH genetic diagnosis, which relies on accurate LDLR variant classification. FH VCEP’s guidelines significantly decrease conflicting classifications, which will be especially helpful to the FH community.