Impact of inflammatory status on intestinal iron absorption in older hospitalized patients

Iron deficiency is prevalent among geriatric hospitalized patients, often coinciding with inflammation. This study aimed to determine a critical C-reactive protein (CRP) threshold for sufficient intestinal iron absorption using standardized tests.

This retrospective, cross-sectional study was conducted in a geriatric acute care unit. Serum iron and CRP levels were measured before breakfast and two- and four-hours after ingestion of two iron capsules. Intestinal iron absorption was calculated by subtracting baseline values from those obtained after the test, with an increase of 100 ug/dl indicating sufficient absorption. Patients were categorized into six CRP groups: ≤0.50, 0.51-2.50, 2.51-5.0, 5.1-7.50, 7.51-10.0, and ≥10.1 mg/dl.

The study included 59 participants (73% females, age range 71-99). Iron absorption was highest in groups with lower CRP levels ≤0.50 to 2.5 mg/dl) and declined significantly as CRP increased, particularly beyond 5 mg/dl. The most significant decline was noted in patients with CRP ≥ 10.1 mg/dl. A negative correlation between inflammation, as measured by CRP, and iron absorption was found. As CRP levels escalate, there is a significant reduction in the increase of serum iron levels after 2 h. A regression analysis showed that only elevated CRP levels significantly reduced serum iron increments post-iron supplementation (P = 0.004), while other factors such as age, sex, body mass index, frailty, weight loss, hemoglobin and nutritional status had no significant impact.

A CRP level above 5 mg/dl is indicative of significantly impaired intestinal iron absorption in older patients, underscoring the critical influence of inflammation on iron metabolism.