Development of Clinical Standards of Care for Huntington disease Intermediate Allele Predictive Test Results

Predictive testing for Huntington disease (HD) has been available since 1986. This genetic test has the ability to ‘predict’ whether individuals will develop HD in their lifetime and possibly pass the disease onto their children. Some individuals who undergo predictive testing receive an unusual test result, called an ‘intermediate allele’ (IA), which differs from a gene positive or negative result. While individuals with an IA will never develop HD themselves, there remains a risk that their children or grandchildren could subsequently develop the disorder. Currently, knowledge gaps exist with respect to IA for HD. Specifically, the current International Predictive Testing Guidelines do not address the possibility of this result, nor are the complexities surrounding this result acknowledged in the literature. Alicia Semaka’s research, which is the largest empirical study on HD IAs to date, will not only address these gaps, but also inform the development of clinical standards of care for communicating IA results during predictive testing. The specific objectives of Ms. Semaka’s research are to determine the prevalence of IAs in British Columbia’s general population; determine quantified risk estimates for the likelihood that an individual with an IA will have a child who will develop the disease in their lifetime; and lastly, describe the psychological and social impact of receiving an IA result. Collectively, the three objectives of this unique, multidisciplinary study will provide the foundation for the development of clinical standards and practice recommendations for IA predictive test results. These standards will help ensure that this subset of patients receive appropriate information, support, education and counselling throughout the predictive testing process.