Bridging the gap between bench and clinic: the importance of understanding the mechanism of iodinated contrast media hypersensitivity.

Since the advent of CT, iodinated contract media (ICM) has become one of the most regularly administered intravenous medications in clinical settings. Although considered generally safe, ICM is one of the most common causes of adverse drug reactions in clinical practice, accounting for more than 2 million adverse reactions worldwide. Currently, there are few useful tools to diagnose patient hypersensitivity, with the major limitation being the lack of consensus regarding the mechanisms of hypersensitivity to ICM. While there is an overwhelming abundance of literature pertaining to clinical features including incidence, symptomatology, and risk, few studies have further investigated the underlying mechanisms behind their clinical observations. Of the available literature discussing pathophysiology, most primary studies were completed over 20 years ago, since which the molecular characteristics of ICM have changed. Furthermore, many reviews mentioning pathophysiology fail to adequately emphasize the clinical importance of understanding the molecular pathways involved in hypersensitivity. In this review, we aim to emphasize the clinical relevance of pathophysiology as it relates to the prediction and diagnosis of hypersensitivity reactions to ICM. To this end, we will first briefly characterize hypersensitivity reactions to ICM with respect to epidemiology and clinical presentation. We will then present the existing evidence supporting various proposed mechanisms of hypersensitivity, highlighting the gaps that remain in the mechanistic delineation of both immediate and delayed reactions. Finally, we discuss the possibility of in vitro testing as a way to predict and diagnose hypersensitivity reactions, pending a more complete elucidation of mechanisms.