Laboratory hemostasis

Speaker: Giuseppe Lippi (IT)

Recorded on 19th December 2017 at h. 18.00 CET

Hemostasis is a complicated mechanism finalized to preventing unjustified bleeding during vascular injury, or unwarranted thrombosis when the vessels are substantially intact. Hemostasis is typically classified in two essential steps. The first event is an endothelial injury, which activates primary hemostasis and is then followed by activation of secondary hemostasis. Specifically, primary hemostasis develops with recruitment of a many platelets being at site of vascular injury. Platelets are subjected to a sequential process of activation, adhesion and aggregation. This initial hemostatic plug is however unstable, since it is vulnerable to fast dissolution within in the local blood, especially in arteries. To prevent dissolution, additional fundamental mechanisms of secondary hemostasis (also known as blood coagulation) are activated, with the aim to stabilize the initial plot by large fibrin deposition.

The diagnostics of bleeding disorders of primary and secondary hemostasis remains a challenge for laboratory professionals, especially those lacking experience background, experience and skill on this topic. Bleeding is essentially due to many acquired or congenital conditions, impairing either primary or secondary hemostasis. A universal consensus on the diagnostics of bleeding diseases remains an unmet target, so that the aim of this Webinar is providing practical guidance for laboratory professionals who are less familiar with this important area of in vitro diagnostic testing. A practical strategy for diagnosing bleeding disorders of primary and secondary hemostasis is necessarily based on a multifaceted and multistep strategy, entailing accurate personal and family history collection, interpretation results of the so-called first-line hemostasis tests, then followed by interpretation (when necessary) of second- and third-line test to identify the both nature and severity of bleeding disease.

The observation of profound hemorrhages rather than muco-cutaneous bleeding suggests a disorder of secondary hemostasis. Although positive family history can be frequently seen in patients with congenital disorders, the absence of clinically significant symptoms in relatives cannot be considered always suggestive of acquired disorders. The next phase is based on performance of the so-called first-line coagulation tests, mainly represented by activated partial thromboplastin time (APTT), prothrombin time (PT) and fibrinogen, especially when the family history is not indicative of specific factor deficiencies. The observation of abnormal results of these tests and the combination of results can help driving performance of the so-called second-line tests, which especially entail clotting factor assays. The so-called third-line tests (especially entailing immunologic tests of coagulation factors and molecular biology) are then useful to make a final diagnosis and/or for detecting the specific nature of the protein deficiency.