Thesis

Impact of intermediate allele results in Huntington disease testing: three patients' perspectives

Huntington disease (HD) is a progressive neurodegenerative disorder that has been studied and well described for over one hundred years. Testing for HD results in a clearly positive result if CAG is > 40 CAG repeats, clearly negative result if CAG is < 26 CAG repeats and there are nuances for interpretation between 27 – 35 CAG repeats (intermediate allele range) and for 36 – 39 CAG repeats (reduced penetrance range). Interpreting the test results for HD can be more complex than originally thought. Predictive test results in the intermediate allele (IA) range have traditionally been thought to be benign to the tester but with expansion possible in future generations. Recent research has demonstrated that some individuals with IA CAG repeat range may exhibit psychological burden beyond that expected and greater than reported for individuals with a wild type HD gene. The purpose of this study was to assess the psychosocial adjustment of individuals with an IA test result following predictive testing. Interviews were conducted with 3 individuals who received an IA test result, which included the administration of two standardized measures of depression, stress and anxiety (the DASS-21 and PHQ-9). While these individuals scored below the clinically diagnosable range for depression on these two measures, all three experienced uncertainty and apprehension about their future and that of future generations. Conversations with these individuals have highlighted the need for continuing research in delineating a psychological profile of individuals who receive an IA test result, with low threshold for referral to psychological services.

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