Canine heterophilic antibodies as a source of false-positive B-type natriuretic peptide sandwich ELISA results.
BACKGROUND
Interference by heterophilic antibodies is a well-known cause of false-positive sandwich ELISA results in human medicine. They are considered rarely in veterinary species and have not been characterized but could become important as newer, highly sensitive sandwich immunoassay technologies are developed.


OBJECTIVE
The goals of this study were to use a B-type natriuretic peptide (BNP-32) sandwich ELISA to determine the effect of heterophilic antibodies on test performance; to characterize canine heterophilic antibodies; and to develop and test a method for heterophilic antibody removal.


METHODS
A sandwich ELISA was developed using a mouse IgG(1)K monoclonal and a rabbit polyclonal antibody to two synthetic peptides of canine BNP-32. The effects on false-positive results of heterophilic antibody depletion and blocking by various techniques were compared. The titers of canine heterophilic antibodies were compared with various blood antigens from other species and the relative amount of canine IgG was compared with that of IgM heterophilic antibody.


RESULTS
Heterophilic antibodies in dog plasma were shown to be capable of causing false-positive ELISA results. They reacted with blood proteins from a variety of animal species at relatively low titers and consisted of both IgG and IgM. Protein A agarose antibody precipitation, in conjunction with mouse IgG(1)K blocking antibody, was effective in eliminating false-positive sandwich ELISA results while retaining adequate test performance.


CONCLUSIONS
Canine heterophilic antibodies can interfere with sandwich ELISA assays and cause false-positive test results. An effective technique for their removal that has a potentially broad application was developed, and allows measurement of canine blood constituents at low picomolar concentrations.
Solter
Philip F
PF
College of Veterinary Medicine, University of Illinois, 2001 S. Lincoln Drive, Urbana, IL 61902, USA. psolter@uiuc.edu
Oyama
Mark A
MA
Sisson
D David
DD
D000818:Animals; D000910:Antibodies, Heterophile / Q000378:metabolism*; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary*; D005189:False Positive Reactions; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D011485:Protein Binding
D000910:Antibodies, Heterophile; D020097:Natriuretic Peptide, Brain