Abstract: Method for the determination of an analyte in a volume of a fluid sample, in particular of anti-TSH receptor autoantibodies in a patient serum, in which one or more determination reagent(s) which contains or which containa) a predetermined amount of a binder (B) for the analyte (A) andb) a predetermined amount of a competitor (K) which is likewise bound by the binder (B), in such a way that the extent of its binding to the binder (B) is correlated with the simultaneous presence of the analyte (A) and/or its amount in the sample, the competitor (K) being labelled, or being capable of being labelled, with a label which permits its qualitative and/or quantitative determination, is or are added to the sample with the formation of a liquid reaction mixture, whereinc) the liquid reaction mixture is reacted simultaneously or subsequently with a solid phase to which a substance (Imm) for the selective immobilization of the amount of competitor (K) not bound to the binder (B) is bound, and optionally with a labelled r