A genetic test can have different types of utility, including clinical utility and social utility, according to Robert Nussbaum of the University of California, San Francisco. Clinical utility is a measure of how valuable a test result is to a patient and a clinician in making decisions about whether to do further diagnostic testing or end the “diagnostic odyssey” as well as in deciding how treatment is managed or how lifestyle should be altered. A test that leads to a diagnosis may have tremendous utility for a patient and clinician, but a third-party payer wants the test to result in an action that makes a measurable difference in health. Individual patients may have the option to pay for a test out of pocket if third-party payers refuse to provide reimbursement, but in that case, Nussbaum observed, many people will be excluded because they cannot afford to pay for the test.

In addition to clinical utility, a test must have social utility if private and government insurers are to be willing to pay for it. The insurers need to be convinced that a new test, when compared with current standards of care, would lead to improved health by reducing the need for less successful therapy and would decrease costs by preventing more costly outcomes. “You have to convince them that it is worth their paying for it as opposed to paying for other things,” Nussbaum said.

Critical Assessments of Genomic Testing for Prevention

Nussbaum outlined six areas in which whole-genome sequencing could be used in a clinical setting and described the common criticisms that arose during discussions with his colleagues. First, whole-genome testing could have clinical use for the identification of carriers of Mendelian disorders prior to conception. At this point it is far less expensive to test for most of the common autosomal recessive conditions than to perform complete genome sequencing. Although the sequencing coverage is not complete for the tests currently used to detect autosomal recessive genes, current standard practice probably continues to be cost-effective compared to the use of whole-genome sequencing for the same indication, Nussbaum said.

A second area, the use of genomics in prenatal and pre-implantation testing, raises many issues, Nussbaum said. “A very serious decision has to be made under severe time pressure with unclear genotype and phenotype correlation.” Pre-implantation testing has advantages over prenatal testing, but it is often limited by the amount of tissue available. This could change with the development of epiblast biopsies to take the place of single-cell testing.

Identification of personal risk for Mendelian disorders is a third area that also raises unanswered questions, especially with regard to clinical

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