Abstract: The present invention relates to a method for improving the specificity of a specific binding assay by adding methyl orange to a coating solution in an amount sufficient for improving specificity of an immunoassay conducted using said coating. The present invention also relates to a method for the detection of antibodies to hepatitis C virus is performed by, i) providing a solid phase comprising a coating solution comprising methyl orange and at least one first binding ligand for antibodies to hepatitis C virus; ii) contacting the solid phase with a sample that may contain antibodies to hepatitis C virus; iii) contacting the solid phase with at least one second binding ligand for antibodies to hepatitis C virus, said second ligand labelled directly or indirectly with a detectable group and iv) measuring the amount of the detectable group bound to the solid phase.