Chris Kresser: So I did some research on it and read some studies, and I’m going to just kind of briefly summarize its use and sensitivity and specificity. I also talked to a gastroenterologist friend who used to be the Chief of Gastroenterology at Columbia in New York before he moved out here. He’s now in Oakland. Certainly the serology can play a role, just as I said it could with the LabCorp IBD panel, but it generally should not be used on its own because it’s not sensitive or specific enough. In a recent large study, the sensitivity of the Prometheus IBD testing was 80 percent, and the specificity was 61.5 percent. In particular, the specificity is quite low, so a negative result on this test would certainly not rule out IBD. A positive result makes it more likely, but a negative result isn’t going to rule it out. Just stepping back a little bit, the difference between the IBD panel that I had mentioned in the unit and the Prometheus Serology is that Prometheus adds some genetic markers that aren’t included in that IBD panel and, I think, a few more antibody markers as well.
If you look at the positive predictive value of the test, it’s about 77 percent, and the negative predictive value is about 70 percent. In lay terms, it means that 23 percent of people who are diagnosed with Crohn’s by the test don’t actually have it and 30 percent of the people that show up with negative results for Crohn’s do actually have it. Those are fairly high numbers. It doesn’t mean that this test isn’t useful. I think it is in the context that I recommended serology for IBD in the gut unit, but as you can see, it’s definitely not a replacement for endoscopic examination to confirm or rule out Crohn’s … or the MRE, which is magnetic resonance enterography. That’s a newer test. It’s basically an MRI of the abdomen and pelvis, and it is around 93 percent specific. It’s probably the least invasive way of getting a fairly clear idea of whether IBD is present. If you suspect it from stool testing and the serology is positive or equivocal, that could be followed up with an MRE. I don’t think I mentioned that in the gut unit. I’ll have to go back and add it. This is a relatively new test with relatively new research on it, but it’s a really good option, especially if you think that the patient will be sensitive to a colonoscopy.