Coagulation

CLOTTING INVESTIGATIONS

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.

Docuementation is available regarding coagulation dosing range form the Pharmacy Department. Please follow this link for further information: http://194.101.238.20/ClinGuide/NEW_index.asp?Spec=51

Sample Collection

Collection of blood from patient must conform to the West Dorset General Hospitals NHS Trust Policy on venepuncture.

Blood for coagulation investigations needs to be collected into plastic Monovette tubes containing 32 g/L. Trisodium citrate dihydrate solution 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.

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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.

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.

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