I think we need to separate the notion of diagnostic biomarkers and outcome biomarkers. The 2 day CPET is currently an outcome biomarker. So are other things in all probability, but they need more work. Our first widespread diagnostic test might not go to the core of the disease process/es. In time these will be identified though, and we will get better biomarkers. The issue with the 2 day CPET to me is that its been around since the first half of last century, and its an obvious test. From a clinical perspective it tells you, objectively, what treatment is doing. This is critical from a clinical outcomes viewpoint. I don't think its an ideal test, I suspect it may be rapidly superseded, but its what we have now.