There are few data available regarding iron parameters in pre-dialysis patients with chronic kidney disease (CKD); it is unclear if there is an association between abnormal iron balance and increased mortality. Using data from the Veterans Affairs Corporate Data Warehouse, Monique E. Cho, MD, and colleagues conduced a historical cohort study to examine the relationship between iron status and mortality. Results were reported in Kidney International [doi.org/10.1016/j.kint.2019.04.029].
The researchers identified a cohort of pre-dialysis patients with CKD with a minimum of one set of iron indices between 2006-2015. The cohort was divided into four iron groups based on the joint quartiles of serum transferrin saturation (percent) and ferritin concentration (ng/mL): (1) reference (16%-28%, 55-205 ng/mL); (2) low iron (0.4%-16%, 0.4-55 ng/mL); (3) high iron (28%-99.6%, 205-4941 ng/mL); and (4) functional iron deficiency (0.8%-16%, 109-2783 ng/mL).
Matching weights based on multinational propensity score models and Poisson rate-based regression were used to compare mortality risk between the iron groups. The researchers also evaluated whether there was a difference between diabetic and nondiabetic subgroups in the association between iron groups and mortality.
Of 87,067 eligible veterans, 32,489 were successfully matched. Mean follow-up was 4.0 years. During follow-up, the adjusted relative rate (95% confidence interval [CI]) for all-cause mortality in the three abnormal iron groups was increased compared with the reference group: functional iron deficiency, 1.21 (95% CI, 1.17-1.25); low iron, 1.10 (95% CI, 1.07-1.14); and high iron, 1.09 (05% CI, 1.06-1.13). For each iron group, the mortality risk was similar between diabetic and nondiabetic subgroups.
In summary, the researchers said, “Thus, an abnormal iron balance, particularly functional iron deficiency, is associated with increased morality in CKD.”