To the Editor.—
Predictive testing for Huntington's disease (HD) using restriction-fragment length polymorphism markers is being conducted at The Johns Hopkins Hospital. During the development of this genetic linkage test, surveys of those at risk for HD indicated that the majority of those asked, between 73%1 and 77%,2 would make use of a safe and reliable predictive test. In the only population-based survey of at-risk individuals, the proportion indicating a desire for testing was 56%.3 Surveys undertaken since the announcement of the predictive test suggest that the number of at-risk individuals intending to make use of this test remains high.4 Our experience to date suggests that, when actually offered the opportunity to discover whether they have inherited the marker for HD, the number of people opting for testing is significantly lower than the population-based survey suggests.
In November 1986, we mailed letters announcing a research