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Abstract
Objectives We studied association of laboratory testing beyond the international normalised ratio (INR) with bleeding and stroke/transient ischaemic attack (TIA) outcomes in patients with atrial fibrillation treated with warfarin.
Design This was a retrospective nested case–control study from the Finnish Warfarin in Atrial Fibrillation (FinWAF) registry (n=54 568), reporting the management and outcome in warfarin-anticoagulated patients. Associations of blood count test frequency and results were assessed together with risk of bleeding or stroke/TIA during 5-year follow-up.
Setting National FinWAF registry, with data from all six hospital districts. Follow-up period for complications was 1 January 2007–31 December 2011.
Participants A total of 54 568 warfarin-anticoagulated patients.
Results The number of patients with bleeding was 4681 (9%) and stroke/TIA episodes, 4692 (9%). In patients with bleeds, lower haemoglobin (within 3 months) preceded the event compared with the controls (median 126 vs 135 g/L; IQR 111–141 g/L vs 123–147 g/L, p<0.001), while patients with stroke/TIA had only modestly lower INR (median 2.2 vs 2.3; 1.8–2.6 vs 2.1–2.7, p<0.001). When the last measured haemoglobin was below the reference value (130 g/L for men, 120 g/L for women), the OR for a bleeding complication was 2.9 and stroke/TIA, 1.5. If the haemoglobin level was below 100 g/L, the complication risk increased further by 10-fold. If haemoglobin values were repeatedly (more than five times) low during the preceding 3 months, future OR was for bleeds 2.3 and for stroke/TIA 2.4.
Conclusions The deeper the anaemia, the higher the risk of bleeding and stroke/TIA. However, INR remained mainly at its target and only occasionally deviated, failing to detect the complication risk. Repeated low haemoglobin results, compatible with persistent anaemia, refer to suboptimal management and increased the complication risk in anticoagulated patients.
- Stroke
- Thromboembolism
- Bleeding disorders & coagulopathies
Data availability statement
Data are available upon reasonable request. Deidentified aggregated data are available upon reasonable request from the corresponding author (TAH, ORCID ID 0000-0002-5273-8088, tuukka.helin@hus.fi).
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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Data availability statement
Data are available upon reasonable request. Deidentified aggregated data are available upon reasonable request from the corresponding author (TAH, ORCID ID 0000-0002-5273-8088, tuukka.helin@hus.fi).
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Footnotes
Contributors TAH, PR, ML, JH and RL contributed to the planning and design of the study. TAH and JH did the statistical analyses. TAH, PR, ML, JH and RL contributed to the reporting of the results and preparation of the manuscript. TAH, PR, ML, JH and RL have all read and approved the final manuscript. RL was responsible for the overall content as the guarantor.
Funding This study was supported by Bristol-Myers Squibb, Finland; Pfizer, Finland; the Finnish Foundation for Cardiovascular Research; and Helsinki University Hospital District Research Fund (grant number Y2016SK007).
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
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