ANTI Xa (ANTI FACTOR Xa)

ANTI Xa (ANTI FACTOR Xa) - plasma

Specimen: 4.5 mL blood added to 0.5 mL citrate.

Method:

(i)	Chromogenic assay; residual factor Xa measured after neutralisation with AT III.Chromogenic substrate is activated by residual factor Xa.

(ii)	Coagulation-based assay.

Therapeutic Interval: 0.3-0.5 U/mL. Consult pathologist.

Application: Monitoring of (full dose) low molecular weight heparin (LMWH) therapy is rarely required, except in renal failure or other situations where there is an increased risk of bleeding. Monitoring of routine LMWH prophylaxis is not cost effective, is not required to achieve clinical efficacy and is not indicated to predict risk of bleeding, which is minimal with LMWH.

Interpretation: Consult pathologist.

Reference: Walenga J et al. Thromb Res (Suppl IV) 1991; 49-62. Hirsch J and Levine MN. Blood 1992: 79: 1-17.