Risks and benefits of population-based genetic testing for Mendelian subsets of common diseases were examined using the example of colorectal cancer risk.
OBJECTIVE
Genetic testing for adult-onset, common diseases is becoming more commonplace in clinical medicine. We modeled the proportions of hypothetic populations that would potentially benefit or suffer harm from widespread predisposition testing.


METHODS
Using the traditional two-by-two table from the discipline of epidemiology, we modeled three hypothetic populations using the example of genetic testing for hereditary colorectal cancer in three groups: the general population, a genetically increased-risk population, and a population at increased risk due to nongenetic factors.


RESULTS
We demonstrate that the potential benefits are increased and risks are reduced when testing is limited to those at increased genetic risk when compared with testing in the general population. Where disease incidence is increased due to nongenetic factors, genetic testing has the potential to detract from the detection and reduction of other potentially important risk factors.


CONCLUSIONS
While targeted testing can benefit those truly at increased risk, broadly applied genetic testing can do more harm than good.
Madlensky
Lisa
L
University of California, San Diego Cancer Center, 9500 Gilman Drive, La Jolla, CA 92093-0901, USA. lmadlensky@ucsd.edu
McLaughlin
John R
JR
Carroll
June C
JC
Goel
Vivek
V
Frank
John W
JW
D000328:Adult; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000235:genetics; D003153:Community Health Services; D005188:False Negative Reactions; D005189:False Positive Reactions; D005192:Family Health; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005820:Genetic Testing / Q000379:methods*; D006801:Humans; D015994:Incidence; D009154:Mutation / Q000235:genetics; D009786:Occupational Health Services; D011159:Population Surveillance / Q000379:methods; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012307:Risk Factors