Nineteen studies were included in the review (n=2,827): two RCTs and 17 prospective studies. Four studies mentioned using a genetic counselling protocol. two studies used a standardised counselling script and three studies used audiotapes to check session content; the other studies used none of these.
Overall, studies indicated that genetic counselling had a positive effect on risk perception accuracy. Some studies found no effect or detected an effect only for low-risk individuals.
Studies that assessed the proportion of participants who accurately estimated their risk showed an average increase in correct perceptions of approximately 25% (range 2% to 55%). An average of 42% of people estimated their risk correctly before counselling and an average of 58% did so after counselling. An average of 25% (range 5% to 76%) continued to overestimate risk and 19.5% (range 7% to 55%) continued to underestimate risk.
Studies that assessed changes in average overestimation of participants' perceived risk found an average overestimation of approximately 18% (range 6% to 40%) after counselling in comparison with 25% (range 11.5% to 42%) before counselling. Across the studies, average decrease in overestimation was approximately 8%.
Results that linked content of the sessions to risk perception accuracy gave mixed results.