Coagulation Laboratory Introduction

Routine Coagulation Testing:

The Coagulation section offers a 24 hour service for all routine coagulation testing, which includes Prothrombin time (PT/INR) Partial Thromboplastin Time (PTT), Fibrinogen level and D-Dimer assay. For urgent requests during core hours (08:00-20:00) please call ext 16920 or 0121 3716920 to obtain an urgent reference number.

Special Coagulation Testing:

The coagulation section also offers a comprehensive range of specialist coagulation assays; these include Factor Assays, Inhibitor Assays, Anti-Xa Assays, Thrombophilia screening, von Willebrand screening, Lupus screening, Heparin induced thrombocytopenia (HIT) screening, ADAMTS13 Activity/Inhibitor Assays and Platelet function testing. This service operates routinely Monday to Friday 09:00-17:00. In certain circumstances urgent assays may be performed out of hours by prior arrangement. Refer to the information in the individual test database for sample requirements and for copies of the appropriate request form (external requests only). Please contact Haematology medical staff for further advice on any special coagulation requests.

There is a 24/7 ADAMTS13 testing service in place for urgent requests. Please ensure you contact the laboratory (ext 15988/0121 3715988 during core hours or ext 16920/0121 3716920 out of hours) and a haematology consultant via main switchboard 0121 627 2000) prior to sending samples.

Special coagulation assays are complex to perform and are batch processed within 21 days of receipt, however urgent requests can usually be processed within 24 hours. Please contact the specialist coagulation laboratory to discuss any urgent requests.

Sample collection notes:

The ratio of citrate anticoagulant to blood in the coagulation test tubes is critical and therefore these tubes must be filled to the black fill line indicated on the tube. It is important to ensure that the anticoagulant is mixed adequately with the blood as inadequate mixing may result in a degree of coagulation activation, which may cause abnormal laboratory results. It is also important to avoid tube contamination, for example do not tip blood from EDTA tubes into citrate tubes as this will interfere with coagulation test results. Blood should not be taken for coagulation studies via a line or indwelling catheter which has contained heparin. Even trace amounts of residual heparin will interfere with coagulation test results.

It is important that blood samples for coagulation tests are transported to the laboratory without delay, samples must not be refrigerated or stored overnight. Testing is most accurate if carried out within 4 hours of venepuncture. As the stability of coagulation factors varies, add on telephone requests will be performed at the discretion of the laboratory based on sample viability.

If tests are required on patients taking anticoagulant therapy, the anticoagulant must be stated clearly on the request form. This information ensures that tests are prioritised accordingly and also facilitates the interpretation of results.