The interpretation of genetic risks offered in genetic counselling

Abstract

The final common path of many practical endeavours in clinical genetics, is the proffering of recurrence risks to parents who have had a previous child with a genetic disease. Thus karyotyping, biochemical carrier detection studies, and mathematical approaches such as Bayesian techniques, all have as their common end the calculation of a simple mathematical risk. The consumer acceptance of such risks, that is how the client interprets the proffered risk, is perhaps the most practical aspect of all clinical genetics. Age, personality, prior knowledge of the risk, the ‘risky-shift’ phenomenon, anticipated risk, and an understanding of the general risk background are all important factors which modify the subjective interpretation of risk. The subjective risk scale used by individuals who are confronted with a situation of uncertain outcome, has a finite number of discrete intervals, and is not a continuum. Eighty percent of geneticists themselves use a subjective risk scale of between 5 and 12 intervals, and this scale is neither an arithmetic or a ratio scale, and is in part nominal. In practical genetic counselling, the subjective risk scales of the counsellor and client may not be similar. The counsellor and client often use different risk scales to interpret the fixed mathematical risk involved—scales which differ not only in size of risk intervals, but also in the pattern of such intervals along the length of the subjective risk scale.