A good test is clinically useful
As gene tests are applied to more genes and people, they are detecting
rarer gene variants, those that confer smaller additional risks, and an
increasing number of gene variants of unknown significance (VUS). Amid
the growing challenges of grading ever more variation in normal human
genomes and in genes that contribute to cancer, researchers are using
many different strategies to improve the positive predictive value (PPV)
of the tests. PPV is the most important measure of
clinical
utility of a test \cite{Burke_2014}, being the probability that a positive test
identifies a variant that actually results in a cancer in that person.
Tests can also be clinically useful if they have a high negative
predictive value (NPV) being the probability that a negative test
results in no cancer in that person. Consequently, the more we know
about the gene, genome, heritable cancer predisposition and the person
tested, the higher the predictive values and the greater the clinical
utility of these tests.