They used to test for gliadin-antibodies before. But since then they have found that celiacs in chidlren and adults are probably two different conditions. The old test was not very accurate in adults and could give "false positive results" according to an information page I found. Now they instead test endomysie- or transglutaminas-antibodies for adults. This is considered to be highly accurate according to my GP. (Not sure these antibodies are called the exact same thing in English as in Swedish but it should be something similar.)
A gastroscopy is just the Swedish term for upper endoscopy.
About your other comment, I think that some cases of IBS could certainly be just gluten sensitivity. And after all IBS is just a collection of symptoms and doesn't say anything about the cause of the problem so if gluten would be the underlying problem for some people it may be that a GF diet would actually cure their IBS.