In 2023, a study identified the BRCA1 gene variant in people with Orkney heritage.
Researchers concluded that the Westray variant affected one in 25-50 people with ancestors from the island.
The specific mutation is linked to an increased risk of breast and ovarian cancer in women.
A year later, a second gene change was discovered to be particularly common in people who had descended from Whalsay.
One in 40 people with ancestors from the island are believed to have inherited the mutation.
Testing is currently available for close family members of people with the faulty genes, or people with breast, ovarian or prostate cancer who have Westray or Whalsay ancestry.
The new pilot programme means anyone in Scotland with a grandparent from the islands can take a saliva test, according to the team behind the project.
Testing is to start in Orkney next year before being rolled out to Shetland and then, in 2028, to the Scottish mainland.
