25/02/2026
Ottawa, Ontario — Wednesday February 25, 2026
It can be hard for families to learn what’s causing a rare disease, and while newer testing tools have dramatically improved diagnostic rates, it’s hard to know which tests health systems should be using to give families the best chance of finding a diagnosis. Exome sequencing (ES) is a commonly used genetic screening tool, while advanced techniques like Genome sequencing (GS) are expected to find extra answers but come with a higher cost.
To see if introducing GS provides better real-world diagnostic outcomes for Ontario families, a study co-led by Kym Boycott compared ES and GS in 1,048 kids and adults from genetic clinics across Ontario. The two techniques showed similar diagnostic success rates: 33.8% for ES and 33.6% for GS, both with timely results. There are a few reasons why GS may not show a clear improvement over ES – answers GS might provide were already found by earlier assay testing, and in this pilot some advanced GS analyses were not fully used, potentially narrowing the gap with ES.
The study findings support the use of ES at scale in Ontario to expand local access for families through a centralized model, while at the same time building GS capacity so it can be used strategically for more challenging cases, and staying ready for future GS advancements that may offer better diagnostic success rates for families.