A method for detecting different non-nucleic acid analytes in a sample, the method comprising: (a) providing to a reaction vessel: (i) at least one solid substrate comprising one or more immobilisation agents; (ii) the sample; (iii) at least two different antibody capture agents that bind to at least two different analytes, wherein the at least two different capture agents can be immobilised on the at least one solid substrate; wherein one or more of the at least two capture agents comprises a plurality of ligands for the immobilisation agent and wherein the ligand and the immobilisation agent are a binding pair comprising a peptide-tag and an anti-peptide antibody; and (iv) at least two different detectable agents that bind to the at least two different analytes; (b) washing the at least one solid substrate in the reaction vessel to remove one or more different capture agents and one or more different detectable agents not bound to the at least one solid substrate; and (c) detecting the at least two different analytes in the sample by detecting the presence of the at least two different analytes bound to the at least one solid substrate, wherein said detecting is via detecting the presence of the at least two different detectable agents bound to the at least one solid substrate via the at least two analytes. (a) providing to a reaction vessel: (i) at least one solid substrate comprising one or more immobilisation agents; (ii) the sample; (iii) at least two different antibody capture agents that bind to at least two different analytes, wherein the at least two different capture agents can be immobilised on the at least one solid substrate; wherein one or more of the at least two capture agents comprises a plurality of ligands for the immobilisation agent and wherein the ligand and the immobilisation agent are a binding pair comprising a peptide-tag and an anti-peptide antibody; and (iv) at least two different detectable agents that bind to the at least two different analytes; (i) at least one solid substrate comprising one or more immobilisation agents; (ii) the sample; (iii) at least two different antibody capture agents that bind to at least two different analytes, wherein the at least two different capture agents can be immobilised on the at least one solid substrate; wherein one or more of the at least two capture agents comprises a plurality of ligands for the immobilisation agent and wherein the ligand and the immobilisation agent are a binding pair comprising a peptide-tag and an anti-peptide antibody; and (iv) at least two different detectable agents that bind to the at least two different analytes; (b) washing the at least one solid substrate in the reaction vessel to remove one or more different capture agents and one or more different detectable agents not bound to the at least one solid substrate; and (c) detecting the at least two different analytes in the sample by detecting the presence of the at least two different analytes bound to the at least one solid substrate, wherein said detecting is via detecting the presence of the at least two different detectable agents bound to the at least one solid substrate via the at least two analytes.