296 established.1 An optimal intestinal permeability test should have a number of properties. The test or marker is preferably sensitive, accurate, reproducible and safe in order to assist in diagnosis and monitoring of disease flares. In addition, an in vivo marker should be stable and inert, avoiding metabolism and degradation.1,14 Numerous studies have evaluated intestinal permeability using radioactively 51Cr-labeled ethylenediaminetetraacetic acid (51Cr-EDTA).11,12,25-33 However, these previously published studies have been unable to establish a consistent correlation between 51Cr-EDTA-measured gut permeability and inflammatory disease activity, likely related to relatively small and heterogeneous IBD study cohorts. Apart from this, most of these studies used the less preferred radioactively 51Cr-labeled EDTA, followed by urinary analysis of gamma radiation. Conjointly, its individual performance in clinical practice remains mostly unfeasible due to complex and impractical detection methods.1,29 A similar substance has recently been developed to evaluate intestinal permeability, in which the non-radioactive 52Cr isotope has been incorporated into 52Cr-EDTA. This allows us to measure urinary 52Cr content in a safe, inexpensive and precisely validated manner using the highly sensitive method of Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In contrast to radioactively labeled 51Cr-EDTA, only few studies have evaluated the performance of 52Cr-EDTA as a tracer for intestinal permeability.34-36 Cr-EDTA has proven to be a sensitive marker for human intestinal permeability, both in health and disease.35-39 Cr and EDTA form a stable and inert complex with one of the highest affinity of known metals, without any physicochemical interactions that might be expected to occur.40,41 However, putative correlations between 52CrEDTA-measured intestinal permeability and CD-specific disease parameters have not yet been established. The aim of this study is to evaluate intestinal permeability through measuring 24-h urinary excretion of orally administered 52Cr-EDTA in Crohn’s disease and its association with inflammatory disease activity, disease localization and two key bacterial marker strains of CD dysbiosis (Faecalibacterium prausnitzii and Enterobacteriaceae). Chapter 9
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