Genetic testing for children at risk to be hemophilia carriers

Carriers for hemophilia are at risk for bleeding despite normal or mildly reduced factor 8 or factor 9 activity levels. Genetic testing is necessary to determine carrier status in those at risk and early identification of carriers can inform their bleeding risk. The aims of this single-center retrospective study were to determine the uptake of genetic testing in children at risk to be hemophilia carriers and identify barriers to completion of testing. We identified 64 unique at-risk children assigned female sex at birth under 18 years old, with at least one caregiver participating in a visit between June 2019 and July 2023 with a genetic counselor with expertise in hemophilia. Of all those at risk, 27% (17/64) had undergone genetic testing prior to having genetic counseling at our center, at a median age of 5 years. Of those who had not yet had genetic testing (47/64): insurance prior authorization was initiated for 49% (23/47), testing was completed for 28% (13/47) at a median age of 11 years, and factor activity levels were known or drawn after the visit for 36% (17/47). The primary reason (14/24, 58%) for not initiating insurance prior authorization was not having a known family variant. Because carrier testing for X-linked disorders standardly involves targeted family variant testing rather than full gene testing, increasing the accessibility of carrier testing depends on increasing the accessibility and uptake of genetic testing in affected family members, usually individuals assigned male sex at birth, with a diagnosis of hemophilia. The impact of the decision to pursue genetic testing on current or future family members at risk to be carriers could be included in counseling discussions with individuals with hemophilia and their families.