When I heard that the 2 day test may be the best biomarker for CFS I wanted this test. I know I have a CFS diagnosis, but do I really have CFS? I traveled to Ithaca last month and did the testing with Betsy Keller (who by the way is lovely and was very patient with all my questions.). My results came in and I did not show the second day response on the two measures that are so widely talked about - VO2 Max and AT. Everything was low (really low), but I didn't do any worse day 1 to day 2. (And I will be following up with a cardiologist about those low results.) The one area I showed a difference falls under "hemodynamics" - day 2 my blood pressure failed to increase appropriately during the latter part of the test. What complicates matters is that I have POTS (likely due to autonomic neuropathy) so my lack of BP response may have been a result of this, however, according to Ithaca the fact that it only happened day 2 may mean it was triggered by PEM and therefore, CFS can't be ruled out. Or was it just what my wacky POTS was doing that day and nothing to do with PEM? I wanted to show the second day response because I wanted to fit into a typical CFS pattern and have some more confirmation that this is likely my disease. I've always feared, what if one day there is a good biomarker for CFS and I test negative for it? I've been ill over 16 years with no good explanation, I've been tested for everything under the sun to no avail, I need for this to be it. I was in contact with another person with CFS who had the same outcome on testing... poor results, but consistent both days. Have enough of us had the 2 day testing done to be sure this is our potential biomarker? Are we pretty sure we should be pushing the government on this 2 day issue? What if the second day response became a diagnostic requirement and you did fine on the test? Either I don't have CFS or this isn't a definitive biomarker. Any thoughts are welcome.