If a person has cancer, would that show up in the white blood cells?
It could, but it doesn’t have to. One of the problems with science fiction, especially things like Star Trek, where they have those computers that they wave over people and it tells you everything is right and wrong with them. When you are looking at blood work, there are things called “Limits of detection”, “Limits of error”, and then there is this: You only see that which you are prepared to see and you will only find that which you test to find. So when you do a blood study, and I do some rather substantial panels, very, very comprehensive, you cannot look for everything.
When you look at Quest, and Quest is a pretty decent group, all things considered. Look at their menu of testing. It’s like the size of a small city phone book. The options of test that you can run are enormous.
You are not going to look for everything and you’re not going to find things that are not tested for. If results might suggest cancer, it is an indirect study for the most part. Wonky liver enzymes are very common, but what else causes wonky liver enzyme levels? Autoimmune disorders very commonly cause autoimmune hepatitis. Does that mean you have infectious disease? No. It just simply means that your enzymes are a little bit off.
It is a good question, but do not become too reliant on blood studies to tell you that you have a disease, or even that it’s clinically significant. You have to take these things with a grain of salt.