GeneDx plans long-read genome sequencing to close rare disease diagnostic gaps

GeneDx plans to add long-read whole genome sequencing (lrWGS) to its clinical genome testing, the Maryland company said on 20 October. An early access programme is due to open by the end of the year.

What's new

Most clinical genomes are read in short fragments and pieced back together. Long-read sequencing covers much longer stretches of DNA in one pass, which helps it pick up complex variation, including certain structural variants and repeat expansions, that short-read methods can miss.

GeneDx says it will use data from its GeneDx Infinity rare disease dataset, plus its interpretation experience, to work out where long reads add most diagnostic value. The aim is to offer the test first for eligible patients rather than as a follow-up, cutting the number of tests a family goes through before getting an answer. The company points to collaborations with technology partners but does not name them, and the announcement gives no price.

"Every advancement in genomic medicine should bring patients closer to answers" Linda Genen, MD, MPH, Chief Medical Officer, GeneDx

Not a cold start

GeneDx has been testing long reads for a while. In August 2023 it launched a research collaboration with PacBio and the University of Washington to see whether long-read WGS could raise diagnostic rates in children with genetic conditions. GeneDx agreed to sequence samples from 350 people, using PacBio's Revio system for the long-read work, and to compare the results with short-read data.

ASHG week

The plan landed in a busy conference week. GeneDx had 27 abstracts accepted at the 2026 meeting of the American Society of Human Genetics (ASHG), including a platform talk on using machine learning to prioritise copy number variants. Houston-based Baylor Genetics used the same meeting, held in Montréal from 20 to 24 October, to present genome sequencing data in two platform talks and a poster, covering diagnostic yield in movement disorders and specimen choice for mitochondrial testing.

GeneDx will report third-quarter results on 9 November, according to its news feed.

The bigger picture

Rare disease labs increasingly compete on diagnostic yield: how often a test actually finds the answer. Each extra solved case strengthens the argument to payers and health systems that genome sequencing should come first, not last. Adding long reads is one lever for pushing yield higher, and it brings new work in variant interpretation, validation and reporting.