[Interferences in immunoassays: Mechanisms and outcomes in endocrinology]

Immunoassays are used daily by clinical endocrinologists to refute or confirm a diagnosis, or to follow up the course of a treatment. Immunoassays have become increasingly sensitive, specific and reproducible, so that clinicians have great confidence in their results. However, they do not always yield correct results because interferences still occur. In the first part of this review, immunoassay interferences are described and their mechanisms explained: matrix effects, specificity defaults, interferences from antibodies and binding proteins, or the hook effect. The hormones most frequently concerned by these pitfalls are reviewed, even as strategies used to prevent and minimize interferences. In the second part, the consequences of failure to recognize an interference are reviewed: unjustified clinical decisions (wrong diagnosis, treatment, surgery) and, more exceptionally, publication in the scientific literature of erroneous results. Clinicians may sometimes inform laboratories of an increased risk of interference. In general, clinicians are in the best position to fully validate test results; because only they know all the medical data about their patients. If there is any suspicion of discrepancy between clinical and laboratory data, they must alert the laboratory. This is the only way to better detect and, if possible, eliminate interferences and their regrettable outcomes.