Many tests use antibodies developed in non-human species (mouse, rabbit, goat, other). A human with an antibody to that species may have a false positive assay. Unfortunately this may not be recognized, and the patient may undergo unnecessary surgery or testing.



Term for Antibody



Human Anti-Mouse Antibody



Human Anti-Rabbit Antibody



Human Anti-Goat Antibody



Other species that may be involved:

(1) rat

(2) horse

(3) pig

(4) chicken


Steps in patient evaluation:

(1) Reason for suspicion (unexpected finding, negative workup).

(2) Identification of the animal species used in suspected test.

(3) Testing by another method shows a different result:

(3a) Testing using antibody derived in another species.

(3b) Testing after blocking or absorbing out the interfering antibody.

(4) Demonstration of IgG or IgM antibody to the suspected species in the patient.


Other considerations:

(1) The patient may have a history of exposure to the species in question, often as a pet or administration of a targeted antibody.

(2) The person may have an allergy to the species with IgE antibodies and positive RAST but IgG or IgM antibodies are required for test interference.


Ways to reduce the interference:

(1) immunosuppress the patient (only warranted for targeted therapy)

(2) use engineered reagent antibodies that are less likely to be affected

(2a) humanized

(2b) polyethylene glycolated

(2c) Fab fragments

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