Immunoassays : Say NO to interference !

Immunoassays : Say NO to interference !

Assay Defender® - Total HAMA and interference blocker


Assay Defender®  is a ready-to use assay diluent for reduction of interference caused by HAMA (human anti-mouse antibodies), rheumatoid factors, nonspecific binding, cross-reactivities and matrix effects.
Assay Defender® is particularly suitable for human or animal specimens containing HAMA (human anti-mouse antibodies), AAA (anti-animal antibodies) or other high affinity antibodies.
Assay Defender® can be used as sample dilution buffer for different applications such as ELISA, lateral flow assays or bead-based assays.
Assay Defender® is ready-to-use and available in bottle sizes of 50 mL, 125 mL and 500 mL            


Reason for interference :
Interference in immunoassays can cause false positive and false negative results in routine testing. Reasons for the increas-
ing prevalence of different kinds of interference are for example:
population aging
  • a growing number of patients with:
  • chronic autoimmune diseases
  • allergic and inflammatory diseases
  • a better limit of detection in modern assays
  • more applications of sandwich-assay formats
Interferences can be classified due to their biochemical reasons and impact on assay performance.
Interference caused by antibodies from patient samples
e.g. HAMA (human anti-mouse antibodies), HAAA (human anti-animal antibodies), heterophilic antibodies and rheumatoid factors from patient samples
Interference caused by endogenous components of the sample
e.g. albumins, complement, lysozyme, fibrinogen, α-1 Antitrypsin, atypically high lipid-, salt- or sugar concentrations as well as atypical viscosities
Interference caused by assay components
Assay components - like fluorescent or enzymatic labels - can cross-react with substances from the sample or change binding properties of the assay antibodies
In contrast to conventional HAMA blockers, Assay Defender® enables effective elimination of all kinds of interference and helps to prevent false positive or false negative results.
Normal sandwich assay with no interference → correct result
An interfering antibody forms a bridge between capture and detection antibody → false positive result
Binding of the interfering antibodies to the capture antibody → false negative result
Binding of the interfering antibodies to the detection antibody → false negative result
Components of Assay Defender® prevent binding of the interfering antibody → correct result

Assay Defender®

Assay Defender® is particularly suitable for human or animal specimens containing HAMA (human anti-mouse antibodies) or other AAA (anti-animal antibodies).
Assay Defender® is a ready-to-use dilution buffer for human or animal body fluid specimens. The previously used dilution buffer can be easily replaced by Assay Defender®. Calibrators
must also be diluted in Assay Defender®. Dilution in Assay Defender® can be 1: 2 or higher. A useful dilution factor for most applications is 1: 10 (1 part specimen + 9 parts Assay Defender®).
Assay Defender® excels at preventing false positive results in interference samples. 
Serum samples from patients with rheumatoid illnesses (Sample 1 and 2) were analyzed using an established research ELISA for the detection of hAxl, a biomarker for hepatocellular carcinoma.
Sample 3 is an interference-free sample from a healthy donor. Samples were diluted either in pure PBS-T/BSA, PBS-T/BSA supplemented with a commercially available HAMA Blocker (HAMA
Blocker 3), commercially available ready-to-use HAMA blocking diluents (HAMA Blocker 1 and HAMA Blocker 2), or CANDOR's Assay Defender®. Assay Defender® alone can completely eliminate
interferences and hence give a true negative result (< 25 ng/mL) in both interference samples. The results of interference free samples are not affected by Assay Defender®.