The Burrill Report


With the rapid drop in the cost of whole genome sequencing, there is widely held hope that we will be entering an era of medicine that will allow doctors to predict and prevent disease in part through the information they glean from an individual’s genome. But a new study raises questions about its predictive value.

In a study published in Science Translational Medicine, researchers at Johns Hopkins University used records on thousands of identical twins in registries in several Northern European countries, as well as a registry of twins held by the National Academy of Sciences. Identical twins have matching genomes. The researchers looked at how well the genome predicted an individual’s disease by seeing how often an individual with a specific disease had a twin who also suffered from the same disease. They argue that such an approach would suggest how well genome sequencing could predict risk for disease.

“We believe that genomic tests will not be substitutes for current disease prevention strategies," says Bert Vogelstein, professor of Oncology at the Johns Hopkins Kimmel Cancer Center, co-director of the Ludwig Center for Cancer Genetics. “Prudent screening, early diagnosis and prevention strategies, such as not smoking and removing early cancers, will be the keys to cutting disease death rates.”

The Johns Hopkins team collected information on the incidence of 24 diseases among the twin-pair groups, including cancer, as well as autoimmune, cardiovascular, genitourinary, neurological, and obesity-associated diseases. To predict disease risk, they constructed mathematical models to calculate the capacity of whole genome sequencing to predict the risk of each disease based on typical thresholds used by doctors to initiate preventive or therapeutic measures.

They found that while whole genome sequencing could alert most individuals to an increased risk of at least one disease in most cases, people would get negative test results for the majority of diseases studied. That, they said, could lead to complacency.

For instance, as many as 2 percent of women undergoing whole genome sequencing could receive a positive test result for ovarian cancer, warning of at least a one-in-ten chance of developing the disease during their lifetime. But the remaining 98 percent of women who receive a negative test for ovarian cancer will not be guaranteed a lifetime free of ovarian cancer. Instead, they will have a risk of the disease that will be similar to that of the general population.

Though in general the researchers say the predictive value of whole genome sequencing is limited, they did say that, theoretically, genetic tests could identify more than three-quarters of patients who may develop four of the diseases studied—coronary heart disease in men, thyroid autoimmunity, type 1 diabetes, and Alzheimer's disease.


April 06, 2012
http://www.burrillreport.com/article-predictive_value_of_whole_genome_sequencing_questioned.html