Combined use of molecular and biomarkers for presymptomatic carrier risk assessment in familial adenomatous polyposis: implications for screening guidelines.

Predictive carrier testing for the inherited disorder of familial adenomatous polyposis (FAP) can be conducted using DNA markers linked to the FAP locus. The presence of characteristic hypertrophic retinal lesions has been advocated as useful biomarkers for FAP. We have compared molecular linkage and retinal screening techniques by evaluating the presymptomatic carrier risk of 40 at-risk individuals from 15 FAP families. Linkage analysis was informative in all and retinal lesion analysis in 25 cases. For informative at-risk population, predictive diagnosis by both techniques was completely concordant and identified 15 members at "high" and 10 at "low" risk of inheriting FAP. Because of the unique advantages offered by each technique, a strategy integrating both techniques will increase the number of FAP families that can be screened presymptomatically. Identification of individuals at high risk of polyposis will improve their clinical surveillance and further reduce the incidence of colorectal cancer in FAP families.