Deriving and Using A Risk Figure

Abstract

Risk is a central concept in genetic counseling. Risk is the probability that a particular event will happen. Risks may be discussed in terms of recurrence or of occurrence—the probability that an event will happen again, or that it will happen for the first time, respectively. Risk can also be presented as odds: the ratio of two mutually exclusive probabilities. This chapter provides a basic review of risk assessment, with a particular focus on its application to chromosome abnormalities. The concept of penetrance is introduced. The ways in which risk figures may be conveyed to patients in the clinic are discussed.