077 - Summary Autoantibodies as a source of analytical mistakes
Autor(s): A. Radice, G. Morozzi
Issue: RIMeL - IJLaM, Vol. 2, N. 3-S1, 2006 (MAF Servizi srl ed.)
Page(s): 77-82
Many of interfering factors, such as blood components bilirubin, haemoglobin, lipides, fibrin clots, etc..., have been described and known for decades. Less studied, but not less important, are the interferences caused by endogenous antibodies: heterophilic antibodies, i.e. naturally occurring human antibodies to immunoglobulins of animal origin, but also i) high affinity, human antibodies specific for proteins (Ig) from one or more animal species, ii) rheumatoid factor, iii) autoantibodies and iiii) cryoglobulins. Heterophilic and other antibodies which can interfere in immunoassays have been found up to 40% of normal blood donors. In this report we describe the mechanisms by which heterophilic antibodies can be source of interference in immunometric routine assays and some examples are discussed, in particular human chorionic gonadotropin, myoglobin, troponin, and carcinoembryonic antigen. Other kind of important interferences are not considered in this report, i.e. cryoglobulins that can cause some of interferences on cell count by automatic counters. The aim of this presentation, in fact, is not to list all the test/systems susceptible of interferences from heterophilic antibodies and/ or anti-animal immunoglobulins. The purpose of this report is to attempt to highlight the possibility and the consequences of interferences caused by circulating endogenous antibodies in immunoassays performance, and to point out that the phenomenon is, and will remain, an insidious and unpredictable problem. To detect heterophilic antibody interference in the sample, the first critical step is to suspect it. The starting point is often a clinician contacting the laboratory about a mismatch between the clinical information and laboratory results. On the contrary, clinicians generally trust that the results they get are correct, but this is not always the case. Non specific interferences producing misleading results in immunoassays, should be discussed with the laboratory staff. This is an important discussion to which all clinical chemists should feel invited to plan possible countermeasures. In this paper some methods for avoiding interferences are discussed. However, the current countermeasures do not avoid heterophilic antibody interference completely. Awaiting a radical solution to come, such interferences must be fought on several front, and the use of a simultaneous nonsense assay should be included when possible.