Using the Symmetry Analysis Design to Screen for Adverse Effects of Non-vitamin K Antagonist Oral Anticoagulants

Drug Saf. 2018 Jul;41(7):685-695. doi: 10.1007/s40264-018-0650-6.


Introduction: Knowledge on adverse effects (AEs) related to non-vitamin K antagonist oral anticoagulants (NOACs) in real-world populations is sparse.

Objective: Our objective was to identify signals of potential AEs in patients with atrial fibrillation (AF) initiating NOAC treatment using a hypothesis-free screening approach.

Methods: Using the nationwide Danish registries, we identified patients with AF initiating dabigatran, rivaroxaban, or apixaban between 2011 and 2015 (n = 50,627). Applying a symmetry analysis design, we screened for AEs of NOAC, as reflected by new drug treatments, incident diagnoses, or procedures. For signals with the lowest number needed for one additional patient to be harmed (NNTH), we evaluated whether they likely represented genuine AEs or other types of associations. Signals assessed as potential AEs were grouped into five categories for analysis of effect modification according to patient and drug characteristics.

Results: Of the identified signals, 61 were classified as potential AEs. Most signals could be categorized as the following types of AEs: bleedings, non-bleeding gastrointestinal symptoms, mental disease, urinary tract disorders, and musculoskeletal symptoms. Older age and first-ever use of anticoagulants was associated with strengthening of all "NOAC-adverse effect" associations. Conversely, use of low-dose NOAC and apixaban led to attenuation of most associations.

Conclusion: Through a symmetry analysis-based hypothesis-free screening of large-scale healthcare databases, we were able to confirm well-established AEs of NOAC therapy in clinical practice as well as potential AEs that deserve further investigation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Aged
  • Aged, 80 and over
  • Anticoagulants / administration & dosage*
  • Anticoagulants / adverse effects*
  • Denmark / epidemiology
  • Drug-Related Side Effects and Adverse Reactions / diagnosis*
  • Drug-Related Side Effects and Adverse Reactions / epidemiology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Registries
  • Vitamin K*


  • Anticoagulants
  • Vitamin K