Flipping the Genomic Sequencing Coin
An observer such as myself can get pretty excited when talking to experts about genomic sequencing and the secrets it potentially may unlock to individualized expectations of health or disease risk. What was once the realm of science fiction seems to be realized in modern medicine: a real path to better vigilance, risk management, drug choices and drug metabolism, understanding carrier status and hereditary risks reaching into subsequent generations.
The costs for genomic sequencing are plummeting -- under $1,000 for an individual had become a reasonable target. And the time it takes has been shaved down to about a day.
But, (and there's always a but...) findings from the Johns Hopkins (JH) researchers' evaluation of the predictive value of whole genome sequencing recently were published in Science Translational Medicine, and they pose questions about the value of sequencing for some.
The study involved data of thousands of identical twins. "Johns Hopkins investigators find that genomic fortune-telling fails to provide informative guidance to most people about their risk for most common diseases, and warns against complacency born of negative genome test results," said a Johns Hopkins Medicine news release about the findings.
"Identical twins share the same genome, and if the genome were the determining factor for common diseases, then the prevalence of a specific disease in an individual whose twin has that disease can be used to determine how well whole genome sequencing could predict an individual's disease risk," says Bert Vogelstein, M.D., Clayton Professor of Oncology at the Johns Hopkins Kimmel Cancer Center, co-director of the Ludwig Center for Cancer Genetics, and investigator of the Howard Hughes Medical Institute.
The Johns Hopkins team collected information on the incidence of 24 diseases among thousands of twin-pair groups across the globe, including cancer, as well as autoimmune, cardiovascular, genitourinary, neurological and obesity-associated diseases.Their analysis shows that whole genome sequencing could alert most individuals to an increased risk of at least one disease, signaled by a positive test result, but most people would get negative test results for the majority of diseases studied, failing to forewarn them of the diseases they may ultimately develop.
The investigators say their analysis specifically shows that whole-genome-based tests are not highly informative for predicting cancer in most individuals without a strong family history of the disease. On the other hand, genetic tests could identify, theoretically, 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.
"We believe that genomic tests will not be substitutes for current disease prevention strategies," says Vogelstein. "Prudent screening, early diagnosis and prevention strategies, such as not smoking and removing early cancers, will be the keys to cutting disease death rates."