Georgetown researcher (and executive dean of Georgetown's medical school) Howard Federoff has taken a "systems" approach to diagnostics for certain chronic diseases. By comparing blood samples taken from patients who subsequently developed Alzheimer's to blood samples after the disease has manifested, Federoff has identified markers and created a blood test that is described as "90 percent accurate" (the BBC article does not delve into the ratio of false positives to false negatives) in predicting whether a currently healthy patient is likely to develop Alzheimer's in the following three years. Understandably, this raises some ethical and practical questions. What would you do differently if this test came back positive for yourself? Or for a parent? Here's the (paywalled) paper, at Nature Medicine.