The cognitive and personality profiles of individuals who request preditive testing for Huntington's disease
Date
2014-05-19
Authors
Lucas, Marilyn Doreen
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Abstract
Huntington's disease (HD), first described in 1872, is a
progressive, debilitating, and ultimately fatal,
neuropsychiatric genetic disorder. The discovery of a
polymorphic DNA marker in 1983 closely localised HD to the
short arm of chromosome 4, and the breakthrough finding of
the specific gene responsible in 1993, mapped within a
small segment of 4pl6.3, led to the establishment of
predictive testing programmes from the mid 1980's. Several
psychological investigations arose from these programmes
including whether or not cognitive impairment was present
presymptomatically in those at risk for HD, and whether
those who requested testing were a self selected group. To
date, the results of the neuropsychological studies have
been conflicting and inconclusive. Methodological
limitations and the stressfulness of predictive testing
have probably contributed to the differing findings. The
present study addressed the methodological flaws of
previous studies and specifically controlled for the
psychological experience of being at risk for a life
threatening disease. To this end, 26 individuals at risk,
but presyrrptomat ic, for HD were recruited from the
Johannesburg Predictive Testing Programme. Subjects were
administered a battery of psychological tests prior to
molecular analysis. A carefully chosen control group,
matched for age, sex, and education, and a group of
individuals experiencing a life threatening illness
(without CNS involvement) were administered the same
battery of psychological tests. Molecular analysis
confirmed 11 of the at risk were positive for the gene (HD+
group), and 15 negative (HD- group). Four way analysis of
variance was conducted using the Bonferroni comparison of
variances to detect group differences between the groups.
The results indicated that stress negatively impacted upon
the test performance of the HD- and stress group but not
the HD+ group. The HD+ group showed mild impairment for
declarative memory function. It was concluded that
cognitive impairment was present prior to a clinical
diagnosis of HD. A further outcome of the present study
indicated that those who request predictive testing are
self selected with regard to personality style and their
goals in life. These findings have far reaching
consequences for current and future predictive testing
programmes in general.