[Procedure and initial results of presymptomatic DNA studies in Huntington's chorea].

The availability of DNA-markers more tightly linked to the Huntington's disease locus made presymptomatic and exclusion testing possible with an accuracy of up to 98%. The testing programme started in Leiden in August 1987. In 56 adults with 25% and 50% risks presymptomatic tests were performed. In 8 persons the risk was increased to 98%, in 17 it was decreased to less than 5%. In two instances the test was not informative. The remaining 29 persons have not yet been tested for different reasons. So far 3 exclusion tests were requested: one showed a decreased risk, one has not yet been performed and one request was rejected. The results and the reactions to the test are discussed.