How people in Benin assess a couple's risk of having a baby with sickle cell disease.

Sickle cell disease (SCD) is a genetic disease resulting from the inheritance from both parents of a mutant hemoglobin gene. Its occurrence can, at best, be prevented, and its daily life consequences can, at least, be limited. As the mutant gene is recessive, it should be useful for people living in countries where SCD is endemic to know their own genetic status and that of their actual or potential partner in order to assess the risk of having a baby with SCD. The present study aimed at examining how a convenience sample of 128 lay people and nine physicians in Benin judge the likelihood that a newborn will suffer from SCD as a function of the genetic status of the baby's mother and father. As expected, several qualitatively different clusters of participants were found. A minority (29 %) made judgments that were largely consistent with the correct rule for determining the likelihood of disease. A larger group (37 %) expressed, however, the view that (a) to know a child's likelihood of suffering from SCD, information is needed about the genetic statuses of both parents and (b) this likelihood depends additively on these genetic statuses. Finally, another group (34 %) thought that, if one parent is suffering from SCD or is a carrier of a sickle gene, the likelihood that the child will have SCD is high, irrespective of the other parent's status. Thus, even among a relatively well-educated group of people in Benin, only a minority used the correct judgment rule when assessing the risk of SCD. Work needs to be done to educate the population regarding the proper way to combine information.