Risk Perception and Acceptability of Risk in a Population Tested for CF Carriership. Myriam Welkenhuysen, Lieve Denayer, and Gerry Evers-Kiebooms, Center for Human Genetics, University Hospital, Leuven, Belgium
In Western populations, cystic fibrosis (CF) is the most common lethal autosomal recessive disorder, with a carrier prevalence of 1 in 25 and a disease prevalence of 1 in 2500 live births. The identification of the CF gene in 1989 made carrier detection possible. However, due to the limited test sensitivity, a negative test result is not conclusive: a negatively tested person still has a small chance to carry a rare mutation of the CF gene. Therefore, even if both partners have a negative test result, their risk of having a CF child still is higher than zero. In the Center for Human Genetics in Leuven, carrier testing has been requested most frequently by relatives of a CF patient. The present paper focuses on their perception of the post test risk of having a CF child themselves. The effect of knowing ones own risk status on hypothetical reproductive decision making is also evaluated.
Our sample consists of 126 tested adults who returned a mailed questionnaire and participated in a follow-up interview (1 month later). Males and females are equally presented in the sample; the median age is 29 years. About two thirds of the subjects have a CF patient in their own family and 27% have a CF patient in their partners family. Almost one third of the sample are CF carriers; 67% has a negative test result. Most respondents (95%) correctly remember their test result.
For the analysis of the perception of the post test risk of having a CF child, the subjects are classified according to their objective risk, taking into consideration the partners test result. When both partners tested negatively, 58% of the subjects are not aware of the restrictions of the DNA test and they are convinced that the residual risk of having a CF child is zero. In the case of one positive and one negative test result, 66% are aware of the existence of a residual risk. Nearly half of them (46%) indicate the correct risk interval; 57% evaluate this risk as very low. For carriers who are single or whose partner is not tested (with a post test risk of 1 in 100 versus the population risk of 1 in 2500) understanding of the risk is difficult: their risk estimations are very divergent, with the highest proportion of I don’t know answers. In total, only one fourth of the sample situates the post test risk in the correct answer category, with an overall tendency for the other subjects to underestimate the risk. As expected, the subjective perception of the post test risk is influenced by the objective post test risk: the lower this objective risk, the lower the subjective quantitative and qualitative risk evaluation. The objective post test risk also has an impact on decisions in a hypothetical situation of a 1 in 4 risk of having a CF child: the lower risk groups (when at least one partner has a negative test result) consider more easily to remain childless in this hypothetical situation, while the carriers who are single or whose partner is not tested - and for whom this situation still is a possible one - opt more often for having own children. When asked which risk level would make them hesitate about a pregnancy, a significant trend is observed to accept higher risk levels as the own objective risk is higher. This suggests that the own risk level serves as a point of reference for judging the acceptability of hypothetical risks.