Management and evaluation system. The data from these studies

Management of Warfarin therapy proved to
be challenging, arising speculation that supplementation daily with low levels
of vitamin K may advance anticoagulation control and be clinically beneficial. Hence available medical literature were
studied, specifically inspecting the effect of supplementation with low-dose
vitamin K in reducing adverse effects when taking vitamin K antagonist (VKA)
and for maintenance of the international normalized ratio (INR). Many scientific studies and publications
were searched, looking at precise trials for effect of taking vitamin K
supplementation against placebos in patients taking a VKA. Examples include the
Cochrane Library, the U.S. National Institutes of Health clinical trials, Ovid
Medline database and International Pharmaceutical Abstracts. Further references
from applicable publications were also screened to recognise additional
clinical trials. All studies considered where in the English-language.

Quality of evidence in the abstract
studies were rated by using the grading of the recommendations assessment,
development, and evaluation system. The data from these studies were used to
evaluate haemorrhage, thromboembolic events and the times when INR was within
the therapeutic range.Studies
issued between 1970 and 2012 that fitted the search strategy. All studies
identified were randomized and controlled. The studies were checked for
inclusion by two reviewers, who made sure the studies met all necessary
requirements.Only published studies which included
patients over the age of eighteen were considered. All the patients were also
receiving VKA therapy at the time of their study.A total of 624 studies were found and
screened, however only three studies (626 patients) was Included for the
meta-analysis. The reasons for this can be seen on the tables below:§Research
question not fully addressed (n=475)

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§Not
RCT (n=77)

§Vitamin
K dietary supplementation (n=4)

§Irrelevant
review article (n=18)

§Single
dose vitamin K (n=27)Some of the limitations in this study
includes:

•Missing
relevant studies due to only using studies published in the English language.

•Only
used 3 studies in the meta-analysis, therefore not very representative.

•Lack
of studies in groups with poor INR control.

•Publication bias may be present as English
studies have a higher chance of being published if a positive result is shown.

•Ultimately due to the few number of
studies and unpolished quality of data, the results can not be concluded as
being comprehensively accurate. However, the study showed no correlation
between low doses of vitamin k (100 to 200 ?g)
supplementation and any benefits on lessening adverse effects in patients
taking VKAs. Conversely, a slight improvement was seen of the time in
therapeutic range, on average 3.5% better than a placebo. For patients with
unstable INRs, inadequate data collected meant no accurate deduction can be
made. 

§Other
(n=20)