Iron status is linked to disease severity after avian influenza virus H7N9 infection

The high mortality rate of H7N9 strain of avian influenza virus (AIV) infected patients has been a major clinical concern. Iron overload increases the susceptibility of host for several kinds of microbial infection. However, the study on patients' iron and ferritin status associated with clinical outcome of AIVH7N9 virus infection is poorly understood, and in order to explain the linkage we carried out this study.

We retrospectively collected serum from 46 patients infected with H7N9 virus from the hospital in Hangzhou city, Zhejiang province of China in 2013. We measured the level of serum iron and ferritin by Enzyme-Linked Immunosorbent Assay (ELISA). The correlation analysis of iron and ferritin with disease severity was done by SPSS 16.0 and MedCalc Software.

After H7N9 infection, there is a reduction in iron level and an increase in ferritin, hepcidin and C-reactive protein (CRP) level in patient's serum compared to those of the control (p<0.001), and there's little correlation between procalcitonin (PCT) level and H7N9 infection. At week 1 and week 2 post-infection, serum iron level is much lower and ferritin level is much higher in the patients who died later than those in the patients who survived. The sensitivity, specificity, and Area Under the Curve (AUC) of the assay was calculated with MedCalc software and they were 85.5%, 65.9% and 0.803 for iron and 84.9%, 80.7% and 0.900 for ferritin, 95.2%, 51.1% and 0.684 for PCT and 100%, 94.6% and 0.988 for CRP, respectively.

Our study found that low serum iron and high serum ferritin levels are correlated with the disease severity of H7N9-infected patients and can predict fatal outcomes.