anti-Xa assay


anti-Xa assay for monitoring low molecular weight heparin

Request a test

External requests must use the Great Ormond Street anti-Xa request form. Please also refer to any additional information provided for this test. Download the referral form >

Additional information

Fill exactly to the line indicated on the bottle. Sample must arrive within I hour of collection. Capillary samples are unsuitable for coagulation tests. If the sample is not taken by a peripheral route, it is essential to avoid heparin contamination.

Sending address

Department of Haematology Camelia Botnar Laboratories Great Ormond Street Hospital Great Ormond Street WC1N 3JH

Laboratory service


Sample requirements

1.4ml venous blood, citrate

Turnaround time

24 hours


Upon request

Call in advance?

Please contact the laboratory when sending urgent samples. Samples sent out of hours and at weekends must be arranged in advance with the Haematology Specialist Registrar.


The Haematology Department provides a wide range of specialist tests with a special interest in the diagnosis and monitoring of coagulation disorders.

© 2011 Great Ormond Street Hospital for Children NHS Trust