TSH immunoassays employing scavenging reagents for cross-reacting endocrine glycoprotein hormone analogues

A method for performing a thyroid stimulating hormone (TSH) sandwich immunoassay on a sample, comprising:

• obtaining a fluid sample;
• scavenging interferants in the fluid sample with scavenger beads coated with bead antibodies to follicle stimulating hormone (FSH), luteinizing hormone (LH) and chorionic gonadotropin (CG), wherein the Kd for each bead antibody is less than about 1 nM for FSH, LH and CG respectively, and the Kd of each bead antibody for TSH is greater than 250 nM;
• contacting the fluid sample with at least one signal antibody and an immunosensor having a capture antibody to TSH;
• forming a sandwich complex on the immunosensor, said complex comprising a the capture antibody immobilized on said immunosensor, TSH, and the at least one signal antibody;
• washing uncomplexed signal antibody from the sensor with a wash fluid;
• and
• detecting a signal associated with said complexed signal antibody, wherein the scavenger beads are removed prior to the detection step and interference caused by the interferants is reduced by the scavenging, and
• wherein the dissociation constant (Kd) of the capture antibody and the signal antibody for TSH is less than or about 1 nM.