We have just been told that best practice now dictates that anti x-a's cannot be drawn off central lines. The rationale being that heparin stays in the lumen of the line and skews the results.We have always turned off the heparin for 5 minutes, flushed x 3, drawn the lab and flushed again. Even better if it is a TLC. I have always found that this was "reliable" i.e. the heparin turned up or down and was therapeutic after a couple of labs.I will be researching this on my own but wanted to see if this was 'best practice' where you work.Thoughts?