Viscoelastic Haemostasis

Viscoelastic Haemostasis

Viscoelasticity refers to the property of certain materials to exhibit both viscous and elastic characteristics when undergoing deformation. Blood is a viscous material under normal conditions, however, during the process of coagulation, it loses viscosity and becomes more elastic in nature. Complex clot structure enables clots to resist deformation under shear forces, this ability is called shear modulus (G), or modulus of rigidity, and is a measure of the elastic shear stiffness of a material. With Viscoelastic Haemostasis assay (VHA) systems, even though the term “clot strength” is used frequently, clot stiffness is measured either indirectly or directly.

VHA have the potential to provide a complete picture of all elements of coagulation, clot strength, and lysis in assessing various coagulopathies. Although conventional clotting assays (CCAs) provide informative data on individual elements of coagulation, the presentation of clot formation and lysis visually and at the point of care have likely made VHAs an attractive alternative to CCAs.

Current evidence shows that VHA-based transfusion management algorithms in cardiac surgery, post-partum haemorrhage and major trauma may be beneficial in the identification of abnormal coagulation to guide treatment and in reducing allogeneic transfusion of RBCs, frozen plasma, and platelets which can translate to both a reduction in morbidity and mortality and cost effectiveness.

The Programme is aimed at clinical staff using Point of Care (POCT) devices such as the ROTEM Sigma and TEG 6 devices rather than laboratory personnel using Thromboelastometry (ROTEM Delta) or Thromboelastography (TEG) analysers. The Programme assesses the performance of the devices and the clinical teams in correctly identifying the specific parameters used in the treatment and transfusion algorithms for the different clinical pathways.

Two Lyophilized human citrated plasma samples (including those enriched with unfractionated Heparin) are distributed every 3 months. The Programme assesses the performance criteria relating to qualitative and quantitative analytes. For quantitative analysis, bias and impression are assessed. This programme is provided in collaboration with the External quality Control of diagnostic Assays and tests foundation in the Netherlands (ECAT). The ECAT foundation is a non-profit organisation providing an international EQA for laboratories working in the field of haemostasis and thrombosis. Samples are shared between the two providers as are the anonymised results. This allows for a larger peer group assessment of the results in this highly specialised field.

Key Features:

  • Working in collaboration with ECAT.
  • Large peer group assessment.
  • Suitable for TEG and TEM.
  • Covers the major analytes used in postpartum haemorrhage, post cardiac surgery and major trauma.
  • Milan Model 3 analytical performance specifications used.

2 x 3.0mL
Lyophilised human plasma which may be enriched with unfractionated Heparin

VH Assay parameters used in the main clinical pathways

Viscoelastic Haemostasis Programme* - ROTEM / TEM
ExtemCT (Secs), A5 (mm), A10 (mm), ML (%)
FibtemCT (Secs), A5 (mm), A10 (mm), ML (%)
HeptemCT (Secs), A10 (mm)
IntemCT (Secs)
Viscoelastic Haemostasis Programme* - TEG
CFFA10, MA (mm)
CKR (mins), K (mins), MA (mm)
CKHR (mins), K (mins), MA (mm)
CRTMA (mm), LY-30

*Not Accredited

Related Documents


UKAS Proficiency Testing 4301UKAS Calibration 4301

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