Testing a best practices risk result format to communicate genetic risks

•We developed a novel risk report addressing multiple, common numeracy issues.•Risk accuracy improved with the new risk format regardless of numeracy ability.•“Feelings of risk” were lower with the new risk format regardless of numeracy.•Using numeracy best practices seems to improve numerical genetic risk communication. To investigate the effect of a genetic report format using risk communication "best-practices" on risk perceptions, in part to reduce risk overestimates. Adults (N = 470) from the Coriell Personalized Medicine Collaborative (CPMC) were randomized to a 2 × 2 experimental design to receive a hypothetical "personalized" genetic risk result for leukemia (relative risk = 1.5 or 2.5) through either the standard CPMC report (N = 232) or an enriched report informed by best practices (N = 238). A one-time, online survey assessed numeracy and risk perceptions including “feelings of risk” and a numerical estimate. Regardless of numeracy, participants who received the enriched report had fewer overestimates of their lifetime risk estimate (LRE; odds ratio = 0.19, p < .001) and lower feelings of risk on two of three measures (p < .001). Participants with higher numeracy scores had fewer overestimates of LRE (OR = 0.66, p < .001) and lower feelings of risk on two out of three measures (p ≤ .01); the interaction between numeracy and report format was non-significant. The enriched report produced more accurate LRE and lower risk perceptions regardless of numeracy level, suggesting the enriched format was helpful to individuals irrespective of numeracy ability. Best practice elements in risk reports may help individuals form more accurate risk perceptions.