The psychological complexity of predictive testing for late onset neurogenetic diseases and hereditary cancers: implications for multidisciplinary counselling and for genetic education

Abstract

Increasing knowledge about the human genome has resulted in the availability of a steadily increasing number of predictive DNA-tests for two major categories of diseases: neurogenetic diseases and hereditary cancers. The psychological complexity of predictive testing for these late onset diseases requires careful consideration. It is the main aim of the present paper to describe this psychological complexity, which necessitates an adequate and systematic multidisciplinary approach, including psychological counselling, as well as ongoing education of professionals and of the general public. Predictive testing for neurogenetic diseases — in an adequate counselling context — so far elicits optimism regarding the short- and mid-term impact of the predictive test result. The psychosocial impact has been most widely studied for Huntington’s disease. Longitudinal studies are of the utmost importance in evaluating the long-term impact of predictive testing for neurogenetic diseases on the tested person and his/her family. Given the more recent experience with predictive DNA-testing for hereditary cancers, fewer published scientific data are available. Longitudinal research on the mid- and long-term psychological impact of the predictive test result is essential. Decision making regarding health surveillance or preventive surgery after being detected as a carrier of one of the relevant mutations should receive special attention. Tailoring the professional approach — inside and outside genetic centres — to the families’ needs is a continuous challenge. Even if a continuous effort is made, several important questions remain unanswered, last but not least the question regarding the best strategy to guarantee that the availability of predictive genetic testing results in a reduction of suffering caused by genetic disease and in an improvement of the quality of life of families confronted with genetic disease.

Introduction

The increasing knowledge about the human genome has resulted in the availability of progressively more genetic tests that allow a prediction about the medical future of an individual regarding a specific disease. This type of test, called predictive DNA-test for a late onset disease, has far reaching implications for the test applicants, their family and for the society (Harper & Clarke, 1997). Today predictive DNA-tests are available for two major categories of diseases: neurogenetic diseases and hereditary cancers.

Predictive DNA-tests provide information about the “future health status” of an asymptomatic person. This type of test is very different from most other medical examinations that usually concern the “present health status”. For this reason it is essential to keep in mind that an asymptomatic person with the mutant gene will stay healthy during an unpredictable number of years: the test really concerns PREsymptomatic diagnosis. Moreover, an individual prediction about the exact age at onset, the specific symptoms or the evolution of the disease is impossible. In other words, a degree of uncertainty persists. The differences between predictive DNA-tests and examinations aimed at early diagnosis are so huge that society has not yet sufficiently adapted to this situation. This is true for potential test applicants, for their health care professionals as well as for other groups in society. This lack of awareness may create a situation wherein persons with an unfavourable predictive test result may be considered as affected in a too early stage (in the presymptomatic stage), a risk that should not be neglected. The above mentioned characteristics of predictive testing and the fact that they lead to a new status or psychological identity have far reaching implications for the context in which these tests should be offered as a clinical service. It is of the utmost importance that a real choice about having or not having a predictive test is safeguarded. This choice should be a well-informed, free and personal decision of the test applicant without external pressure. This is the more true because there usually is no urgent medical reason to perform this type of test.

The availability of predictive DNA-tests gives informed people the choice “to know” or “not to know”, a decision with tremendous short-, mid- and long-term consequences. Because of the particular nature of predictive tests for (currently) untreatable late onset diseases, a large amount of international debate and consultation preceded the implementation of the first predictive DNA-tests in clinical practice. The successive guidelines elaborated by the International Huntington Association and the World Federation of Neurology are an example in this context (1994). In the meantime the multidisciplinary approach for predictive testing for Huntington’s disease has been a model for other neurogenetic diseases. Moreover, it has been a very valuable starting point for predictive testing for hereditary cancers. Obviously the detailed approach should be tailored to each specific disease. Therefore one should keep in mind some important differences between predictive testing for “incurable” neurogenetic disease and hereditary cancers, for which “prevention and treatment” may be available. In addition to the availability of preventive measures, the reduced penetrance of specific hereditary cancers in carriers of the mutant gene may be at the origin of different counselling needs. Moreover, attention has to be paid to a particular characteristic of genetic testing for hereditary breast and ovarian cancer. In this situation “diagnostic” testing in affected women also has a “predictive” aspect, because the detection of the mutant gene may imply information about the increased risk of getting cancer in the future, e.g. in the other breast or in the ovaries. The distinction between diagnostic testing and predictive testing is obviously less clear-cut in this particular situation than in the situation of predictive testing for neurogenetic diseases.

It is the main aim of the present paper to describe the psychological complexity of predictive DNA-testing that necessitates an adequate multidisciplinary approach, including psychological counselling. In this context research findings regarding uptake for predictive testing and regarding the psychosocial impact of the predictive test result are also discussed. We focus on two important groups of diseases for which predictive test programmes have been implemented in clinical practice, namely neurogenetic diseases (part 1 of the paper) and hereditary cancers (part 2).

Secondly the paper is aimed at describing attitudes regarding predictive testing in relevant groups of the society, including general practitioners. Their opinions (in part 3) are important because the developments in the field of predictive testing might trigger the general population to seek access to genetic services and because general practitioners can play a considerable role in the field of genetic testing, as gatekeepers or in a more general way.