That False Negative Problem

So whenever you test someone for some disease, you can have a negative, positive, false negative, or false positive.  As far as the falses go, a false positive is probably not that bad.  In the case of our system, that would mean that an output was produced when the person does not actually have cancer. After the output was produced, another test would be performed to actually find the cancer with a scope and it would be discovered that there is no cancer.  Although it would cause the patient a lot of unnecessary grief over their diagnosis, a false positive eventually just ends with the patient being relieved.  A false negative, however, is much more frightening.
Recently, our group discovered a really probable false negative that our system could give when interacting with GI cancer.  Since our system only produced output when Beta-catenin was present without Wnt, the cell would be free to have free Beta-catenin and Wnt and not show that it is cancerous.  If the presence of Wnt and free Beta-catenin was just an occasional occurrence in cancer cells and they would produce the output at all other times, this would not be a problem. However, some cancer cells suffer from hyperactive Wnt (too much Wnt).  Therefore, there would be no output would be produced, but the cell would be cancerous.
We are in the amidst of figuring out how to deal with hyperactive Wnt.  Our current solution is to have two systems.  One system is the old system and the other involves miRNA degrading a second output.  We have also looked at possible ways to use Wnt presence as a repressor and promoter for the same output.  This one-system system would create fewer parts for the cell to produce in order for the system to work, but may be less accurate.  This is a dilemma into which we are still looking.
This issue has made me think of the part of the project on which I was just working. I had to find a way to amplify the output.  I think that we are going to use the modular amplifier that I found even though we have to produce a few more parts.  This reminds me of the two-system vs. one-system debate because it forces the engineer to decide between a larger system built with modular parts vs. a simpler system that is tailored specifically to the issue/goal at hand.  Maybe the second way is better, but I am very grateful that papers have been published and the Registry of Biological Parts has been created to help make the whole field more modular and a little easier to grasp by people just learning things like me.