Serum selenium levels in patients with respiratory diseases: a prospective observational study

Background: Serum selenium levels are lower in critically ill patients as compared with healthy controls. However, there is no data about the difference in serum selenium levels depending on the severity of lung diseases. We aimed to identify the factors associated with low serum selenium levels in critically ill patients with respiratory diseases. Methods: A prospective study was performed in 83 patients with respiratory diseases who had admitted to the intensive care unit (ICU) and general wards. We obtained systemic inflammatory markers, nutritional indicators and prognostic factors as the explanatory variables for the outcome of low serum selenium levels. Results: Serum selenium levels on admission were lower by 28% in the ICU group as compared with the general ward group (70.0 +/- 26.4 and 97.9 +/- 20.8 ng/mL, respectively, P<0.001). Low serum selenium levels had a correlation with malnutrition represented by decreases in levels of lymphocyte (R-2=0.107, P=0.005) and albumin (R-2=0.174, P<0.001). In addition, low serum selenium levels were associated with an increase in baseline C-reactive protein (CRP) (R-2=0.059, P=0.041) and APACHE II scores (R-2=0.209, P<0.001). Lower albumin levels (P=0.032) and higher APACHE II scores (P=0.046) showed a significant correlation with lower serum selenium levels on multivariate analysis. Conclusions: Low serum selenium levels in patients with respiratory diseases have a significant correlation with poor nutritional status and prognosis on admission.