Blocker Selection Guide

Immunoassay Blockers for Heterophilic Interference

Blocker Selection Chart

When designing an immunoassay, part of the assay optimization process includes increasing the assay’s resistance to interference from heterophilic antibodies by adding blockers.

How do you select the right blocker for an immunoassay? There are a few factors that need to be considered: 1. Assay format (e.g. lateral flow, ELISA, chemiluminescence) 2. Source of antibodies in the assay (e.g. mouse, rabbit, goat) 3. Type of inference in the patient sample (e.g. heterophilic antibodies (HA), human anti-mouse antibodies (HAMA), or rheumatoid factor)

IVD manufacturers often use animal serums or purified animal IgG to reduce this interference, however, animal IgGs must be used in high concentration and can only block cross-reactive antibodies from a single animal of origin. Other active blockers, such as TRU Block ™ , can remove many different types of heterophilic interference including HAMA and rheumatoid factor (RF) using a completely new approach. In addition, they can be used at concentrations 10-100x less than animal IgG.

Review the chart below to find the best blocker for your application



Any Antibody







Human Anti-Mouse Antibodies

Heterophilic Antibodies

Rheumatoid Factor

TRU Block # A66800H TRU Block 2 # A66802H TRU Block 3 # A66803H TRU Block Ultra # 8000



TRU Block # A66800H TRU Block 3 # A66803H

TRU Block Ultra # 8000 TRU Block 2 # A66802H

TRU Block Ultra # 8000 TRU Block 2 # A66802H

Mouse IgG # A66186M

Rabbit IgG # A66100H

Chicken IgY # A01460C

Goat IgG # A66200H

Rat IgG # A64391R

Sheep IgG # A66400S

Format-Specific Solutions

Universal Solutions

Animal IgG selected must match the antibody host

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