A combination product for detecting a target marker in a biological sample in combination with a target marker binding molecule which is capable of binding specifically to the target marker, the combination product comprising, at least: (a) a first binding agent comprising a first binding molecule which is capable of directly or indirectly binding specifically to the target marker binding molecule, a labeling substance, and a carrier, wherein the first binding molecule is an antibody or an antigen binding fragment thereof; (b) a linker molecule; and (c) a second binding agent comprising a second binding molecule which is capable of binding specifically to the linker molecule, a labeling substance and a carrier, wherein the second binding molecule is an antibody or an antigen binding fragment thereof; wherein the linker molecule is an antibody, wherein the linker molecule is capable of binding specifically to the labeling substance in the first binding agent and the labeling substance in the second binding agent, wherein the linker molecule is capable of binding specifically to the first binding agent and the second binding agent, and wherein the linker molecule includes at least two binding sites at which the linker molecule is capable of binding specifically to the second binding agent, wherein the labeling substance in the first binding agent and the labeling substance in the second binding agent is the same substance, wherein the first binding agent is a structure in which the first binding molecule and the labeling substance are connected with each other indirectly via a carrier, and wherein the second binding agent is a structure in which the second binding molecule and the labeling substance are connected with each other indirectly via a carrier, and wherein the labeling substance is at least one selected from an enzyme label, a coenzyme label, and a hapten. (a) a first binding agent comprising a first binding molecule which is capable of directly or indirectly binding specifically to the target marker binding molecule, a labeling substance, and a carrier, wherein the first binding molecule is an antibody or an antigen binding fragment thereof; (b) a linker molecule; and (c) a second binding agent comprising a second binding molecule which is capable of binding specifically to the linker molecule, a labeling substance and a carrier, wherein the second binding molecule is an antibody or an antigen binding fragment thereof; wherein the linker molecule is an antibody, wherein the linker molecule is capable of binding specifically to the labeling substance in the first binding agent and the labeling substance in the second binding agent, wherein the linker molecule is capable of binding specifically to the first binding agent and the second binding agent, and wherein the linker molecule includes at least two binding sites at which the linker molecule is capable of binding specifically to the second binding agent, wherein the labeling substance in the first binding agent and the labeling substance in the second binding agent is the same substance, wherein the first binding agent is a structure in which the first binding molecule and the labeling substance are connected with each other indirectly via a carrier, and wherein the second binding agent is a structure in which the second binding molecule and the labeling substance are connected with each other indirectly via a carrier, and wherein the labeling substance is at least one selected from an enzyme label, a coenzyme label, and a hapten. wherein the linker molecule is an antibody, wherein the linker molecule is capable of binding specifically to the labeling substance in the first binding agent and the labeling substance in the second binding agent, wherein the linker molecule is capable of binding specifically to the first binding agent and the second binding agent, and wherein the linker molecule includes at least two binding sites at which the linker molecule is capable of binding specifically to the second binding agent, wherein the labeling substance in the first binding agent and the labeling substance in the second binding agent is the same substance, wherein the first binding agent is a structure in which the first binding molecule and the labeling substance are connected with each other indirectly via a carrier, and wherein the second binding agent is a structure in which the second binding molecule and the labeling substance are connected with each other indirectly via a carrier, and wherein the labeling substance is at least one selected from an enzyme label, a coenzyme label, and a hapten.