Anemia and thrombocytopenia in patients with atrial fibrillation: a nationwide study

Introduction

Anemia is frequently observed in atrial fibrillation (AF). However, limited data is available about anemia and thrombocytopenia, and their impact on oral anticoagulant (OAC) initiation

Purpose

We examined prevalence of anemia and thrombocytopenia in patients with AF and evaluated initiation of OAC according to baseline hemoglobin (Hb) and platelet (PLT) levels.

Methods

This study is part of the nationwide retrospective register-based FinACAF (Finnish AntiCoagulation in Atrial Fibrillation) study, including all patients diagnosed with AF in Finland between 2004 and 2018 (n=411,080) identified from national primary, secondary and tertiary healthcare registries. Laboratory data from the six largest central laboratories were available. Data on OAC purchases were obtained from the National Prescription Register.

Anemia was defined to World Health Organizations (WHO) criteria, Hb <130 g/l in men and <120 g/l in women, and thrombocytopenia as PLT <150 x109/l for both sexes. A sensitivity analysis excluding patients with CHA2DS2-VA-score 0 was performed to restrict analyses to those with an indication for anticoagulation.

Results

A total of 92,547 patients with incident AF with available Hb and PLT values within 7 days before cohort entry were included. Anemia was present in 26.2% (26.8% of men and 25.6% of women) and thrombocytopenia in 9.7%, 12.6% of men and 6.7% of women.

After exclusion of patients with CHA2DS2-VA-score =0 (n=7,544), 28.0% had anemia and 9.9% had thrombocytopenia.

OAC was initiated in 70.6% of patients. Mean Hb was higher among OAC initiators than non-initiators (136.2 g/L vs 131.5 g/L), whereas PLT counts were similar (234.3 vs 238.7 ×10⁹/L). OAC initiation was less frequent in patients with anemia (60.7% vs 74.2%) and thrombocytopenia (62.7% vs 71.5%) compared with those without these conditions.

Patients with both anemia and thrombocytopenia (3.6%) had the lowest initiation rate (50.1%).

Findings were consistent after restricting the analysis to patients with CHA2DS2-VA-score ≥1, with lower OAC initiation in patients with anemia (61.2% vs 78.0%; mean Hb 135.6 vs 128.2 g/L in initiators vs non-initiators) and thrombocytopenia (64.0% vs 74.4%; mean platelet count 234.4 vs 239.3 ×10⁹/L). Baseline characteristics are presented in the Figure.

Conclusions

Anemia was common among patients with AF, affecting more than one in four patients and slightly more often men than women. OAC was initiated less frequently in patients with anemia or thrombocytopenia.Figure 1.