Main analysis
The INR results were measured from 8 weeks before statin initiation to
12 weeks after statin initiation. We graphically depicted the changes in
INR values by mapping median, interquartile and 10thand 90th percentile during this window. To formally
assess the INR changes, we estimated the increase in mean INR by
comparing the latest INR result in the before window to the first INR
result within week 3-6 after statin initiation (if any), by using a
paired t test. We further assessed the median effect by
estimating median changes in INR levels for all statin treated patients,
as well as those treated with a high- (≥40mg) and low-dose
(<40mg) simvastatin in secondary analyses. Finally, we
calculated the proportion of patients with an INR above the therapeutic
interval (for most patients INR between 2-3); defined as INR
> 4 and > 5 by comparing the proportion of
patients 1-4 weeks prior to initiating simvastatin to the proportion 3-6
weeks after.
All analyses were performed using STATA Release 14.1 (Stata- Corp,
College Station, TX, USA). The study was approved by the Danish Data
Protection Agency. Since data is based on anonymized register data
neither approval from Ethics Committee nor collection of informed
consent was needed.