Anti-Coagulation

Introduction

The investigation of bleeding should normally take the form of:-

• Patient's History
• Family History
• The pattern of bleeding
• Physical examination
• Laboratory testing

Because of the complexity of the haemostatic mechanism and the range of investigations available, different laboratories may adopt different procedures.

Sample Collection

Collection of blood from patient must conform to the Dorset County Hospital NHS Foundation Trust Policy on venepuncture.

Blood for coagulation investigations needs to be collected into plastic Sarstedt tubes containing 32 g/L. Trisodium citrate dihydrate solution (blue) as anticoagulant. Nine volumes of blood need to be added to one volume of anticoagulant.

Successful laboratory investigation depends on satisfactory blood samples taken by trained staff. Important aspects include:-

• Minimum of circulatory stasis.
• Clean venepuncture to avoid activation.
• Absence of heparin contamination via in-line catheters.
• Effect of haematocrit on the proportion of plasma to anticoagulant.
• The effect of stress, emotion and physical activity of the patient on certain parameters.

Back to Top

Test Available

• Perform a routine clotting screen - PT & APTT.
• If the PT and APTT results are prolonged and the patient is not already known to the laboratory then perform  further screening tests - TT, REP (if necessary), Correction tests.
• Show results to one of the medical staff and discuss the need for further testing.
• If required, further investigations such as factor assays, inhibitor screening of thrombophilia screening will need to be arranged with the senior member of staff in charge of the section.
• The following tests are available.

TEST	TUBE TYPE
PT	BLUE
APTT	BLUE
Thrombin Time	BLUE
Reptilase Time	BLUE
Fibrinogen assay	BLUE
Derived Fibrinogen	BLUE
Factor II assay	BLUE
Factor V assay	BLUE
Factor VII assay	BLUE
Factor VIII assay	BLUE
Factor IX assay	BLUE
Factor X assay	BLUE
Factor XI assay	BLUE
Factor XII assay	BLUE
Factor VIII inhibitor assay	BLUE
Lupus anticoagulation Screening tests	3 X BLUE
Activated Protein C Resistance	BLUE
Anti-thrombin III assay	BLUE
Protein C activity assay	BLUE
Protein S activity assay	BLUE
Thrombophilia screen (Includes PT, APTT, Lupus anticoagulation Screening tests, Activated Protein C Resistance, Anti-thrombin III assay, Protein C activity assay, Protein S activity assay).	4 X BLUE

 

Further investigations such as von Willebrands factor antigen, Ritocetin cofactor, Multimeric analysis, Factor 13, Factor V Leiden DNA analysis, Prothrombin 20210A DNA analysis and Anticardiolipin antibodies are send away to other reference laboratories.

Back to Top