A patient’s aPTT is determined to be 65 seconds (Ref Range 3…

A patient’s aPTT is determined to be 65 seconds (Ref Range 38-35 secs). The patient’s prior results from this admissions encounter are all within reference limits and they are not receiving anticoagulant therapy. It was noted that the sample was collected from a peripheral IV. You suspect heparin contamination. What test would be the next best test to confirm you suspicion?