He doesn't know your family history; he's never performed a physical exam on you or looked at your blood work. (taliand.com)
If the disease is uncommon, as with the progressive rod - cone degeneration (PRCD) form of Progressive Retinal Atrophy in Australian Shepherds, or if use of a test and careful breeding decisions have markedly reduced the frequency of a formerly common mutation (think what could be done with CEA in Collies,) testing could then be confined to only those dogs with known family history of the disease or with relatives that have been DNA tested as carriers. (ashgi.org)
Our results pointed to three new genetic markers for FECD and confirmed the vital role of a previously known marker even among those who did not have a previously known family history of the disease. (sciencedaily.com)