The anti–factor Xa assay is designed to measure plasma heparin (unfractionated heparin [UH] and low molecular weight heparin [LMWH]) levels and to monitor anticoagulant therapy.
Therapeutic ranges of heparin are as follows:
LMWH: 0.5-1.2 IU/mL
UH: 0.3-0.7 IU/mL
Prophylactic ranges of heparin are as follows:
LMWH: 0.2-0.5 IU/mL
UH: 0.1-0.4 IU/mL