Does Topical Cortisone Cream Affect Blood Test Result?

I am going for a blood test which is going to test me for allergies, coeliacs disease and iron etc [MBA, FBC, Iron study, TSH, endomyseal antibody, tTGA + lgE (Or lgE), RAST panel] and am currently on a course of topical cortisone cream (Eleuphrat ointment - it's like diprosone) for eczema/skin allergic reaction. Can you please tell me if topical cortisone cream can interfere with the results of such a blood test?