Laboratory haematology II – Coagulation and the acute phase response

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Laboratory haematology II – Coagulation and the acute phase response



Simple tests of blood coagulation


Despite the complexity of haemostasis (p. 12), it is possible to make a general assessment of coagulation with a few relatively simple first-line tests. As an initial screen of haemostatic function the following tests should be combined with a blood count and film to determine platelet number and appearance.





Quantitation of plasma fibrinogen


In most laboratories this has replaced the thrombin time as a first-line test. Several accurate methods are available for the quantitative assay of plasma fibrinogen. Fibrinogen is an acute phase reactant (see below) and is frequently elevated in sick patients. Causes of low levels include disseminated intravascular coagulation (DIC) and severe liver disease.


Common clinical causes of abnormal first-line coagulation tests are shown in Table 10.1. Second-line tests may be needed for more precise diagnosis. In mixing experiments (or correction tests) patient plasma is mixed with normal or factor-deficient plasma prior to repeating first-line tests. If a particular coagulation factor is thought to be lacking, a quantitative assay can then be performed. A circulating inhibitor of coagulation is suggested by failure of the coagulation abnormality to be corrected by the addition of normal plasma. Many routine tests are now automated. Most coagulation instruments rely on measurement of changes in optical density to detect clot formation.



Jun 12, 2016 | Posted by in HEMATOLOGY | Comments Off on Laboratory haematology II – Coagulation and the acute phase response

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