BMJ Open 4:e005379 doi:10.1136/bmjopen-2014-005379
  • Cardiovascular medicine
    • Research

Measures of vitamin K antagonist control reported in atrial fibrillation and venous thromboembolism studies: a systematic review

  1. Craig I Coleman1,2
  1. 1Department of Pharmacy Practice, University of Connecticut School of Pharmacy, Storrs, Connecticut, USA
  2. 2The University of Connecticut/Hartford Hospital Evidence-Based Practice Center, Hartford, Connecticut, USA
  1. Correspondence to Dr Craig I Coleman; craig.coleman{at}
  • Received 2 April 2014
  • Revised 22 May 2014
  • Accepted 2 June 2014
  • Published 20 June 2014


Objective To aid trialists, systematic reviewers and others, we evaluated the degree of standardisation of control measure reporting that has occurred in atrial fibrillation (AF) and venous thromboembolism (VTE) studies since 2000; and attempted to determine whether the prior recommendation of reporting ≥2 measures per study has been employed.

Design Systematic review.

Search strategy We searched bibliographic databases (2000 to June 2013) to identify AF and VTE studies evaluating dose-adjusted vitamin K antagonists (VKAs) and reporting ≥1 control measure. The types of measures reported, proportion of studies reporting ≥2 measures and mean (±SD) number of measures per study were determined for all studies and compared between subgroups.

Data extraction Through the use of a standardised data extraction tool, we independently extracted all data, with disagreements resolved by a separate investigator.

Results 148 studies were included, 57% of which reported ≥2 control measures (mean/study=2.13±1.36). The proportion of time spent in the target international normalised ratio range (TTR) was most commonly reported (79%), and was frequently accompanied by time above/below range (52%). AF studies more frequently reported ≥2 control measures compared with VTE studies (63% vs 37%; p=0.004), and reported a greater number of measures per study (mean=2.36 vs 1.53; p<0.001). Observational studies were more likely to provide ≥2 measures compared with randomised trials (76% vs 33%; p<0.001) and report a greater number of measures (mean=2.58 vs 1.63; p<0.001). More recent studies (2004–2013) reported ≥2 measures more often than older (2000–2003) studies (59% vs 35%; p=0.05) and reported more measures per study (mean=2.23 vs 1.48; p=0.02).

Conclusions While TTR was often utilised, studies reported ≥2 measures of VKA control only about half of the time and lacked consistency in the types of measures reported. A trend towards studies reporting greater numbers of VKA control measures over time was observed over our review time horizon, particularly, with AF and observational studies.

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