The current recommendation of 3 months of warfarin treatment after bioprosthetic AVR surgery is primarily based on results from 1 retrospectivestudy with a limited number of events.
For one, the groups noted the analysis is a retrospectivestudy, not a prospective, randomized controlled clinical trial, which many regard as a gold standard for ferreting out safety concerns.
First, it is a retrospective case-control study and is therefore susceptible to reporting bias, meaning that people with ALS may report their coffee consumption differently from controls.