The Effect of Direct Anticoagulant Therapy on Haematological Parameters in Atrial Fibrillation: Clinical Significance of Subclinical Haemoglobin Decrease

<i>Background and Objectives</i>: Direct oral anticoagulants (DOACs) have become the cornerstone of stroke prevention in the management of atrial fibrillation (AF). While their efficacy in preventing catastrophic outcomes is well documented, the exploration of their effects on haematological parameters, particularly in clinically stable AF patients, remains markedly underrepresented in existing research. The aim of our investigation was to delineate the variations in key haematological parameters, with a special focus on haemoglobin (Hb), in a cohort of clinically stable patients afflicted with AF and receiving diverse oral anticoagulant treatments. <i>Materials and Methods</i>: In this retrospective study, 742 patients with AF were evaluated. Following exclusion criteria, 530 patients were included and categorised based on the change in their Hb levels (ΔHb < 2 [<i>n</i> = 473] vs. ΔHb ≥ 2 [<i>n</i> = 57]) after one year of initial prescription of DOACs. <i>Results</i>: Patients in the ΔHb ≥ 2 g/dL group demonstrated significantly higher baseline haemoglobin levels during the pre-DOAC period (13.5 [12.3-14.6] vs. 14.6 [13.1-15.7]; <i>p</i> = 0.002). Baseline haemoglobin was identified as a predictive factor for a decrease in Hb ≥ 2 g/dL, with higher initial values being associated with more pronounced reductions (OR, 95% CI: 1.424 [1.178-1.723]; <i>p</i> < 0.005). This pattern was observed consistently across various types and dosages of DOACs. <i>Conclusions</i>: This study underscores the importance of vigilant clinical monitoring for anaemia in patients undergoing DOAC therapy, even when their clinical course appears to be stable.