FISH stands for Fluorescent in situ hybridzation. It is a procedure - not a test in that you can test for a wide variety of genetic conditions using this technique.
Suppose you know that a gene that you know is responsible for a specific disease. This is one gene among 50,000 so finding this one gene in a cell could be difficult. BUT, supposing you had a compound which - when it binds to that one gene - will fluoresce and be picked up by photo sensitive instruments.
So - there are lots of tests out there that use FISH technology.It is just that you might not know which tests since most tests will not be identified as such since it is a technique.
Gayle, At the present time, there are quite few opinions about the use of molecular testing for CLL. One side holds that all forms of cutting edge test must be done while an opposing side says that there is not enough evidence that the answers are meaningful and that you get all the information you need/want through a careful examination of patient progress. Of course, there are also people in between who get the information if they fell there is reason to do so (infections, unusual symptoms, etc.) and there are people who will get the information just in case some years down the line it might be useful.
The biggest problem with all DNA - based testing right now is that it is so new it is hard to determine if it is meaningful or not. For example - it is statistically meaningful to have a blood glucose change from an 80 to a 94 but it is clinically irrelevant in that both values are perfectly adequate numbers. It may be clinically significant that someone has a gene for some abnormal hemoglobin but if it happens that this hemoglobin works ok, then for the individual,it is a useless bit of information in reality.
Sorry I can't really answer your question but we won't have that answer for a few years. I guess the best answer is that you need the results that make you comfortable.
Flow cytometry results (if that is what you are referring to) usually mean negative = less than 10% of the cells are visualized by the "stain" positive = more than 20% of the cells are visualized by the "stain" I've put stain in quotation marks because it is really a combination of monoclonal antibodies directed against a specific antigen marker on the cell and some type of fluorescent compound. When the antibody/fluorochrome is bound to the cell, the fluorochrome emits energy that is picked up by light sensitive photomultiplier tubes and reported as a positive. Many systems are closed in that the operator never sees the energy burst or, since different fluorochrome do indeed give off different colors, any color change so the v visualization is entirely performed by the instrument.