 - Enoxaparin last known anti-factor Xa prior to enrollment if available must confirm heparin has been administered If a pre-study aPTT or anti-factor Xa is not available, subsequent testing of the study phlebotomy or a phlebotomy as a part of routine medical care taken before or during the time of the study phlebotomy must confirm the presence of heparin unfractionated or low molecular weight in order for that data point to be included in the analysis. 