Serum iron levels are an independent predictor of in-hospital mortality of critically ill patients: a retrospective, single-institution study

Objective This study aimed to examine the relationship between serum iron levels and in-hospital mortality in critically ill patients. Methods We retrospectively studied 250 critically ill patients who received treatment at the intensive care unit between June 2015 and May 2017. Blood chemistry and hepatic and renal function were measured. Kaplan-Meier survival curves were plotted according to serum iron levels. Correlations between serum iron levels and other variables were analyzed. Results A total of 165 (66.0%) patients had abnormally low serum iron levels (<10.6 mol/L). Patients who died during hospitalization had markedly higher Acute Physiology and Chronic Health Evaluation II scores and significantly lower serum iron levels compared with those who survived. Cumulative survival was significantly lower in patients with low serum iron levels than in those with normal serum iron levels in subgroup analysis of older patients (n=192). Multivariate regression analysis showed that, after adjusting for relevant factors, low serum iron levels remained an independent risk for in-hospital mortality (odds ratio 2.014; 95% confidence interval 1.089, 3.725). Conclusions Low serum iron levels are present in a significant proportion of critically ill patients and are associated with higher in-hospital mortality, particularly in older patients.