title: The use of vitamin K supplementation to achieve INR stability: a systematic review and meta-analysis.
abstract: OBJECTIVE
  Systematically review and quantitatively synthesize evidence on use of oral vitamin K supplementation in reducing international normalized ratio (INR) variability.
  
  
  METHODS
  PubMed, The Cochrane Library, PsycINFO, Cumulative Index of Nursing and Allied Health Literature (CINAHL), Turning Research Into Practice (TRIP), Web of Science were searched for studies meeting predetermined inclusion/exclusion criteria. Five studies meeting criteria (three randomized trials, one quasi-experimental pre-post study, one retrospective case series) were appraised for quality and data synthesized by two reviewers. Pooled effect size of time in INR therapeutic range (TTR) was estimated using random effects meta-analysis.
  
  
  CONCLUSIONS
  Pooled effect size representing data from four studies (678 subjects) was 0.31, 95% confidence interval 0.03-0.59 (Cochran Q = 7.1; p = .07; I(2) = 57.8) and favored vitamin K supplementation. Given wide variability among individual studies, there is not enough evidence to advise for or against the routine use of vitamin K supplementation to achieve INR stability. However, evidence does suggest that it may be of some benefit for some patients with INR instability.
  
  
  CONCLUSIONS
  There is insufficient evidence to support routine supplementation with vitamin K in patients on chronic anticoagulation therapy but select patients, particularly those with persistent INR instability despite known adherence to regimen and no dietary or drug-drug interactions, may benefit from the intervention. Future research is warranted.
authors.affiliation: (Staff Associate in Neurology), Weill Cornell Medical College, New York, New York, (Nurse Practitioner), Columbia University Medical School, New York, New York, (Assistant Professor of Clinical Nursing), Columbia University School of Nursing, New York, New York.
authors.forename: Melissa
authors.initials: M
authors.lastname: Kramps
authors.forename: Abigail
authors.initials: A
authors.lastname: Flanagan
authors.forename: Arlene
authors.initials: A
authors.lastname: Smaldone
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects; D019587:Dietary Supplements; D006801:Humans; D019934:International Normalized Ratio; D014812:Vitamin K / Q000627:therapeutic use*; D014815:Vitamins / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014815:Vitamins; D014812:Vitamin K
keywords: Nurse practitioners; cardiovascular; meta-analysis; safety