The invention relates to a compilation of detection reagents, wherein the compilation comprises a first and a second detection reagent, wherein the first detection reagent binds non-mutated leptin with a first binding value, but does not bind mutated leptin or binds it with a maximum of 50% of the binding value of non-mutated leptin, and wherein the second detection reagent binds both mutated and non-mutated leptin with a second binding value. The invention furthermore relates to an in-vitro method for detecting mutated leptin and the use of a detection reagent.