There Will Be Blood Tests

Historically, blood has been a powerful symbol, conferring familial membership, bestowing the right to rule, and representing human vitality. Throughout both history and literature, from Sleeping Beauty to Harry Potter, a drop of blood has often had immense consequence. Beyond these fantastical purposes, blood is indeed growing in power, with multiple recent advances harnessing the potential of scientific discoveries to use patients’ blood to detect a plethora of diseases, from malaria to cancer. The harnessing of blood to diagnose physical conditions is not new. The complete blood count (CBC) is routine, and blood counting as a diagnostic method has been in use since the 19 century. Other common blood tests in the clinic include those for liver function, blood glucose levels, and prostate cancer. These tests exploit various components of blood, including cell-free DNA, secreted proteins, and characteristics of blood cells themselves. Using the same underlying premise, but by combining novel scientific discoveries and technological advances, researchers today are greatly expanding the capability of blood tests to illuminate the state of our health. In a recent study published in Science, Joshua Cohen et al. have advanced the utility of liquid biopsies to detect and even distinguish multiple cancers (Cohen et al., 2018). The authors developed a new blood test, termed CancerSEEK, which combines assays for 2,001 common driver mutations with assessment of eight cancer-associated protein biomarkers, synergizing to successfully identify eight cancer types at various stages with an overall detection sensitivity of 55%. Excitingly, the results of CancerSEEK, when combined with a supervised machine-learning approach, were sufficient to localize the anatomic site of the tumor in a large majority of cases. Importantly for a screening approach, the test is