Skip to main content

Please note that this is a beta version of our website. Should you encounter any bugs, glitches, lack of functionality or other problems on the website, please let us know immediately so we can rectify these accordingly. Your help in this regard is greatly appreciated! You can email us.

Login to North West London Pathology – consumables service

If you need a new account or you have a query about your order, please telephone the pathology call centre on 0203 313 5353.

If you have forgotten your password you can reset this yourself. Please click here if you have forgotten your password.

Results Line and Enquiries

0203 313 5353

Heparin assay (Anti Xa assay)

Category Haematology >> Specialised Coagulation Services
Test background

The anti FXa assay is the method of choice when monitoring low molecular weight (LMW) heparin therapy, and can be a replacement for the APTT test when monitoring therapy with unfractionated heparin. Anti-Xa may be used to monitor some patients who have ‘heparin resistance’ (ie. do not respond as expected to UFH) or who have an underlying condition or interfering factor(s) that alter the APTTR test result. Low molecular weight heparin (LMWH) therapy is usually not monitored, but it may be necessary to monitor anti-Xa in some cases, such as in patients who are pregnant, obese, very young, elderly and those who have kidney disease or dysfunction (given that LMWH is primarily cleared from the body by the kidneys). Any condition that decreases kidney function can potentially decrease LMWH clearance, increasing its concentration in the blood and increasing the potential for excessive bleeding.

Clinicial Indications

Monitoring heparin (especially LMWH) therapy in patients who are pregnant, obese, very young or elderly and those with renal impairment.

Sample & container required 4.5 mL sodium citrate (pale blue top) adults; 1.8 mL sodium citrate (pale blue top) paediatrics
Sample volume 24 hours
Notes

Special handling: avoid prolonged stasis during venepuncture. Sample must be received by lab within 4 hours of collection. Please note: samples will be rejected if underfilled or overfilled.