Preprint: expanded gnomAD v4.1 data shifts variant classifications for globin gene loci

A preprint posted to bioRxiv by researchers at Cold Spring Harbor Laboratory analyses how the substantially enlarged Genome Aggregation Database (gnomAD) version 4.1 affects variant interpretation at the globin gene loci involved in sickle-cell disease, thalassaemias, and related haemoglobinopathies. The study examines eight genes across the alpha-globin locus (HBA1, HBA2, HBZ) and the beta-globin locus (HBB, HBD, HBG1, HBG2, HBE1).

gnomAD v4.1 offers substantially greater sample sizes and improved ancestry stratification compared with v2.1.1, the version on which many existing variant classifications were based. The authors assess how this expanded population evidence alters fulfilment of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) variant classification criteria — specifically criteria that use allele frequency as evidence for or against pathogenicity. Variants that previously met a threshold for population frequency evidence may cross reclassification boundaries when re-evaluated against the larger dataset.

The work has direct relevance for molecular diagnostic laboratories and genetic counsellors working in haemoglobinopathy services, as reclassification of variants in these genes can affect carrier screening programmes, prenatal counselling, and the interpretation of variants of uncertain significance (VUS). Because gnomAD itself does not include disease cohorts, allele-frequency evidence is one of several criteria that laboratories must weigh alongside functional and segregation data.

This is a preprint and has not yet been peer-reviewed. Findings should be interpreted accordingly and are not a basis for immediate changes to laboratory practice without further validation.