BACKGROUND: The prevalence of iron deficiency (ID) in chronic thromboembolic pulmonary hypertension (CTEPH) is poorly documented, and the impact of ID on anaemia, pulmonary hemodynamics and muscle function in CTEPH remains to be explored. The criteria used to define ID can determine both its prevalence and its clinical consequences.

METHODS: In a group of 167 consecutive patients with CTEPH eligible for balloon pulmonary angioplasty (BPA), the prevalence of ID was compared using either the definition endorsed by PH guidelines (ferritin<100 ng/mL or 100-299 ng/mL with transferrin saturation (TSAT)<20%), or a definition based solely on TSAT<20%. The associations between ID and anaemia, resting hemodynamics, 6-minute walk distance (6MWD) and peak oxygen consumption (VO₂) were studied with these two definitions of ID.

RESULTS: Only 31/167 patients (19%) had anaemia. The prevalence of ID was much higher with the definition of the PH guidelines than with the definition based solely on TSAT (67% vs. 43%; p<0.001). The definition of the PH guidelines did not identify patients with reduced peak VO₂, 6MWD and peak exercise power, but defining ID as TSAT <20% did, even after adjustment for age, sex, height, and haemoglobin. However, whatever the definition, patients with and without ID had a similar prevalence of anaemia and similar hemodynamic parameters.

CONCLUSION: ID is common in CTEPH patients eligible for BPA, most often without anaemia, and its prevalence depends critically on the definition used. Defining ID solely as TSAT <20% may allow to identify a subgroup of patients with reduced exercise capacity.