With the increasing complexity of modern medicine, we now have literally thousands of possible investigative techniques at our disposal. We are able to examine our patient’s serum and every other body fluid down to the level of individual nucleotides, as well as being able to perform precise imaging through CT, MRI and other imaging technologies. The problem we have all faced, especially as senior medical students or junior doctors is: which test should we use in a given setting? What hazards are associated with the tests?.