Laboratory investigation of Bleeding Disorders

 Laboratory investigation of bleeding disorders is set up for patients who have a history of Spontaneous bleeding or excessive bleeding after trauma or surgery. The tests are also undertaken for bleeding tendency in patients who have to undergo major surgery.

Acquired haemorrliagic disorders are more common than inherited disorders, and platelet disorders are more common than the coagulation disorders. In patients with inherited bleeding disorders, a family history must be investigated. Among the inherited coagulation disorders, factors VIII and IX deficiencies are the most common. They are transmitted as sex-linked disorders and affect males while females act as carriers of the recessive genes. Other inherited disorders of coagulation such as factor XI deficiency are transmitted as autosomal disorders and occur with equal frequency in males and females. The common causes of acquired bleeding disorders are thrombocytopaenia (which can occur by a variety of immune, non-immune, infectious and drug-induced, and malignant conditions), deficiency of vitamin K (due to hepatic or obstructive jaundice), therapy with the Coumadin group of drugs and others, disseminated inravascular coagulation (DIC), gammopathies and liver failure.

 Various haemostasis tests are performed to identify bleeding disorders or to follow up anticoagulant therapy. These tests are either done on the patient (like bleeding time) or the patient’s plasma is taken for laboratory coagulation tests (like PT, APTT). In most cases, citrated blood is used for getting the plasma. 

The principle behind these laboratory tests calls for reagents, supplied by commercial companies that have ingredients at different levels of coagulation pathways. Patient’ s plasma supplies the missing factors and the time taken for the formation of clot determines the possible insufficiency in the patient's plasma as compared to the normal plasma (normal time). The time taken for the formation of clot is determined either manually or by an automated system. 

 Testing for the detection of fibrinogen degradation product (FDP) is called for when there is high clinical suspicion for DIC or pulmonary embolism. In case of a positive finding, confirmatory tests must be done to detect abnormalities in platelet function or deficiency of specific coagulation factors and defects in the fibrinolytic system. In any case of pancytopaenia or severe thrombocytopaenia, where the diagnosis cannot be made with peripheral blood, bone marrow aspirate must be obtained to exclude the possibility of acute leukaemias.

 

BASIC SCREENING TESTS FOR BLEEDING DISORDERS
 

Two basic screening test 

         -  Bleeding Time (BT)

         -  Clotting Time (CT) 

These two tests are commonly used in the coagulation Laboratories of developing countries for the presumptive diagnosis of bleeding disorder in a patient.

 

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