Are hydrogen breath tests (to test for lactose, fructose, and lactulose intolerances) very accurate? How accurate are they (generally speaking)?

THERE ARE LIMITATION. There are limitations to hydrogen bresth testing for bacterial overgrowth of the small bowel with lactulose can diagnose 60%of cases, this is because strict criteria are used to interpret the test, if less strict criteria are used many more overgrowth will be diagnosed.Some do not have bacteria that produce hydrogen and it can not be tested and some have slow transist through small bowel and takes5h.