This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Laboratory monitoring of which of the following is desirable with low molecular weight heparin therapy: March 2012 
Select and explain. 
A. aPTT, B. CT, C. PT, D. Anti-factor Xa activity
D: Anti-factor Xa activity
Answer: D: Anti-factor Xa activity 
Explanation: Ans: D i.e. anti-factor Xa activity Laboratory monitoring of anticoagulant LMW heparin selectively inhibit factor Xa with little effect on Ha. So LMW heparins have smaller effect on aPTT and whole blood clotting time. Since aPTT/clotting times are not prolonged, laboratory monitoring is not needed LMWH therapy is monitored by the anti-factor Xa assay, measuring anti-factor Xa activity.