Two new SIBO tests have come out. Curious about your thoughts. First one isn’t a new test so much as it’s a new combo of pre-existing tests. BioHealth recently announced that they have a combo package where one can do both the glucose and a lactulose SIBO test. Given the fact that they involve two 24-hour prep diets and two three-hour test periods, are there clinical situations in which you would see the utility for such a double test?

Chris Kresser:  Not really. I’d have to think about it a little bit. I think lactulose is much more sensitive than glucose, so it would be unusual to have someone who was positive for glucose but then negative for lactulose. It would, however, not be unusual to see someone who was negative for glucose and then positive for lactulose. You could set that up in a kind of reflex manner where you start with glucose, and then if the glucose is negative, you go on and do lactulose. If the glucose is positive, you stop, and you don’t have to go forward with lactose because if the glucose is positive, they almost certainly have SIBO. But as I’ve argued in the SIBO diagnostic unit, if we’re there yet, glucose favors specificity over sensitivity, so there’s a greater chance of a false negative and less chance for false positive. Lactulose favors sensitivity over specificity, so it’s the other way around. There’s a greater chance of a false positive and a lower chance of a false negative. Because the treatments for SIBO are relatively benign compared to treatments for other conditions like autoimmune disease, for example, I favor a higher risk of a false positive than a false negative. If we know the limitations of lactulose testing, which I’m teaching you and you understand how to interpret the test, I think you can minimize that to some degree. You don’t just go by the machine generated criteria. You actually use what you learn in this course to interpret the test. I think lactulose is still the best method, and a lot of patients have trouble with even the single preparation for the SIBO test. It’s the least popular test to prepare for, so putting them through that too for two cycles right there in a row I think is probably not necessary.