Cancer Sniffing Dogs

Two dogs that have been trained to sniff urine for traces of prostate cancer are 98% accurate, according to a new paper. But since existing blood tests are only 80% accurate, how do they know the dogs are wrong 2% of the time? Maybe the dogs are always right and the doctors are wrong 2% of the time.

There is nothing surprising about this; people can learn to smell advanced cancer, and anything people can do with their noses dogs can do a thousand times better. Dogs detect individuality at the genetic level -- to bloodhounds, identical twins smell like the same person no mater what you do to disguise their scents. Since cancer is genetically different from other cells, of course it smells different to them. The interesting question would be about the threshold, and whether dogs can  make diagnoses early enough to be medically useful.