Q: In ICUs what is the most common cause of falsely positive Ant-Xa assay level?


Answer:  In ICUs Anti-Xa assay is usually obtained on patients who are getting infusion of IV Heparin. If level is drawn from the same line or nearby ports running Heparin, Anti-Xa assay would be falsely elevated. Second major cause of falsely elevated Anti-Xa  assay is compromised renal function.