The role of ferritin subunits in the diagnosis of iron deficiency in patients with pulmonary hypertension

Background . Iron deficiency (ID) is a common issue among patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH), negatively impacting their exercise tolerance. Identifying latent iron deficiency in these groups is challenging due to the influence of chronic inflammation on interpreting iron metabolism markers. The L- and H-subunits of ferritin are promising candidates for assessing iron deficiency. Objective is to evaluate the possibilities of using ferritin subunits in the differential diagnosis of absolute and functional (against the background of inflammation) iron deficiency in patients with variants of precapillary pulmonary hypertension. Methods . Study involved 20 PAH and 47 CTEPH patients undergoing echocardiography, right heart catheterization, 6-minute walk tests, and lab assessments of heart failure, inflammation, and iron metabolism. Results . Moderate correlations were found between serum ferritin (SF) and its subunits with MCP-1, which indicates the role of inflammation in changing ferritin levels. The increase in SF in the CTEH group is due to the L- and H-subunits. The study also showed correlations of both ferritin subunits with markers of iron deficiency, such as TSAT and sTfRF, but there were no differences in the ratio of subunits at absolute and functional ID. Conclusion . Findings provide insights into SF/subunit correlations with inflammation/iron markers in PAH/CTEPH, though their utility for differential diagnosis remains limited. The results of the study are important for understanding the mechanisms of iron deficiency in PAH and CTEPH.