The effect of acute and chronic inflammatory response on plasma and erythrocyte selenium concentrations: Implications for assessing selenium nutritional status

Summary: Background: Selenium is an essential trace element and its deficiency can lead to dysfunction in multiple areas. Selenium status is commonly assessed by its measurement in plasma but this may be an unreliable marker in patients with systemic inflammatory response (SIR). Erythrocyte selenium is an alternative marker that appears not to be perturbed by the SIR. Objectives: Examine the effect of the magnitude of acute and chronic SIR on plasma and erythrocyte selenium concentrations. Methods: Acute inflammation: Blood samples were collected in patients (n=16) undergoing elective knee arthroplasty pre-operatively and post-operatively (24 and 48 hours and 3 months). Chronic inflammation: Blood samples were collected in patients receiving nutritional support who presented for routine micronutrient screening (n = 3798). CRP was used as a marker of inflammation. Plasma and erythrocyte selenium concentrations were divided into 3 inflammatory groups: minor, moderate and major defined as CRP<10, 11–80, >80 mg/L. Results: Plasma selenium concentrations reduced with increasing CRP concentrations from minor to moderate to major inflammation (P<0.001), whereas erythrocyte selenium concentrations only reduced in chronic major inflammation. In both acute and chronic inflammation, median plasma selenium concentrations were within the local laboratory defined reference interval (0.75–1.50 μmol/L) with minor and moderate inflammation, whereas in major inflammation they were below the reference interval. In contrast, median erythrocyte selenium concentrations remained within the local laboratory defined reference interval (3.0–9.0 nmol/g haemoglobin) in the context of minor, moderate and major inflammation in both acute and chronic inflammation cohorts. Furthermore, in the chronic inflammation cohort, concordance between plasma and erythrocyte selenium concentrations at the lower limit of the reference intervals decreased from 84% of patients with minor inflammation, to 66% and 44% in patients with moderate and major inflammation respectively. Conclusion: In both acute and chronic inflammation, plasma selenium concentrations fell significantly with rising CRP, whereas erythrocyte selenium concentrations were less affected. IRAS: 225557. ClinicalTrials.gov: NCT03554668.