Interference in immunoassay is an underestimated problem

Abstract

The presence of antibodies in some patients' serum has long been known to be a potential source of interference in immunoassays, as shown by numerous case reports. These often appear after the introduction of a new analyte (e.g. troponin) and then decrease in number as the topic becomes exhausted. This highlights the persistent and intrinsic nature of this problem, despite attempts by the manufacturers to compensate for this source of error. However, an explanation of the immunoanalytical basis underpinning these assays could be more effective in raising awareness than intermittent case reports. In this review we have outlined the use of antibodies as reagents, the factors determining how they bind to antigen(s), and the nature of the immune response in order to explain the insidious and unpredictable nature of this form of interference. Studies on the prevalence of interference have yielded values ranging from 0.05 to more than 2%. However, these figures are analyte- and assay-specific, influenced by the study design, and are not therefore generally applicable. It is also highly likely that figures on prevalence and incidence will worsen in the future because of the wider use of monoclonal antibodies as diagnostic and therapeutic tools. Clinical laboratories should be alert to assay interference from antibodies irrespective of its nature, as immunoassays will remain an indispensable analytical tool, unlikely to be replaced in the foreseeable future by a practical alternative.

Heterophilic antibodies may be a cause of falsely low total IGF1 levels

“…Nonlinear sample dilution has been recognized as a method to identify samples with interference (12,27). However, this is not universally successful.…”

Pseudohyperthyroxinemia in a hypothyroid patient secondary to chronic phlegmon

“…Elevated fT 4 and normal or high (non-suppressed) TSH Repeat fT 4 Normal or low fT 4 Elevated fT 4 Serum thyroglobulin Interference in immunoassays is serious but often unrecognized [13]. Interference can be analyte dependent or independent and may increase or decrease the measured result.…”

Steroid measurement with LC–MS/MS in pediatric endocrinology

“…Other steroids of similar structure and abundance in the circulation cause assay interference, especially in the newborn period. Although immunoassays use liquid-liquid extraction to eliminate interfering compounds, these methods are still susceptible to interferences from other endogenous steroids (Ismail et al, 2002). Extensive and laborious sample pretreatment lowers the overall efficiency and makes these methods awkward for practical use in a clinical laboratory.…”

“…Several LC-MS/MS methods have been described for the quantification of testosterone in serum/plasma to overcome this problem (Cawood et al, 2005;Ismail et al, 2002;Kushnir et al, 2006a;Moal et al, 2007;Rauh et al, 2006;Singh, 2008;Taieb et al, 2003).…”