“Heterophile antibodies are a well-recognized cause of erroneous results in immunoassays. We describe here a 22-month-old child with heterophile antibodies reactive with bovine [Cow] serum albumin and caprine [Goat] proteins causing false-positive results to human immunodeficiency virus type 1 and other infectious serology testing.”
“We believe the positive test results observed in this patient were due to heterophile antibodies reactive with BSA and caprine proteins. All of the positive tests observed used BSA [bovine serum albumin] as a blocking agent for the preparation of the microELISA reaction wells.”
“Anti-BSA antibodies have previously been investigated in the pathogenesis of diabetes mellitus (1), but their prevalence and interference in immunoassays are not known. Conceivably, anti-BSA antibodies could be quite common, since most immunoassays use BSA in the specimen diluent, so that in most instances these antibodies would be preabsorbed and not detected.”
It seems that even though they knew of the possibility of positives due to the test materials, they did not study it (“not well characterized”):
“Heterophile antibodies reactive with other molecules used in immunoassays have not been well characterized but can also cause false assay results (4).”
“Monoclonal antibodies used in diagnostic assays are produced using animal cells, usually from mice. The Achilles heel of this apparently highly specific assay principle is that many individuals, possibly up to 40% of the general population, possess naturally occurring antibodies to animal immunoglobulins (eg, to mouse, rabbit, cow, rat, goat), termed heterophilic antibodies.”
“If an individual with heterophilic antibodies against mouse immunoglobulins has a test by an immunoassay that uses mouse monoclonal antibodies, then the heterophilic antibodies can also form links between the capture and signal antibodies, generating a false-positive signal” White GH. Trusting numbers: uncertainty and the pathology laboratory. Med J Aust. 2002 Aug 5;177(3):153-5.