{"id":4635,"date":"2021-02-23T19:27:56","date_gmt":"2021-02-23T18:27:56","guid":{"rendered":"https:\/\/meddists.com\/learn\/clinical\/hematology\/hemostasis\/hemostatic-tests\/"},"modified":"2021-05-31T15:22:00","modified_gmt":"2021-05-31T13:22:00","slug":"hemostatic-tests","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/clinical\/internal-medicine\/hematology\/hemostasis\/hemostatic-tests\/","title":{"rendered":"Hemostatic tests"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><div class=\"intro\">Hemostatic tests are useful for the assessment of the function and integrity of blood vessels, platelets, and coagulation factors.<\/div><\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Description<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">Bleeding disorders can stem from abnormalities in:<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>Blood vessels<\/li><li>Platelets<\/li><li>Coagulation factors<\/li><\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Hemostatic test<\/strong> are used for testing the hemostatic system and serve as an important diagnostic tool to help assess the function of the components mentioned above:<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>Blood count<\/li><li>Blood smear<\/li><li>Plasma fibrinogen<\/li><li>Bleeding time<\/li><li>Coagulation test (APTT, PT, TT)<\/li><li>Platelet function tests<\/li><\/ol>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Blood count, blood smear smear, and plasma fibrinogen<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<p class=\"wp-block-paragraph\">Blood count and smear are the first lab tests to be performed; they can diagnose thrombocytopenias among many other blood disorders (leukemias, anemias).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Normal plasma fibrinogen is 1.5-4.5g\/L.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Bleeding time<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<p class=\"wp-block-paragraph\">No longer used in practice; involves performing a small and shallow prick on the surface of the forearm to induce bleeding, and measure how long does it take for the bleeding to stop by soaking the blood with a the edge of a piece of paper.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This test is supposed to check the action of platelets.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Coagulation tests (APTT, PT, TT)<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<p class=\"wp-block-paragraph\">Coagulation tests involve taking a patient&#8217;s plasma and adding different components to stimulate a situation where the different pathways of the coagulation cascade are activated.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">We measure the time it takes the plasma to coagulate and compare it to the norm.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>APTT (activated partial thrombin time)<\/strong> tests the intrinsic and common pathways.<ul><li>Phospholipids, activator (kaolin, silica), and calcium are added to citrated plasma<\/li><li>APTT measures factors XII, XI, IX, VIII, along with factor X, V, II, and fibrinogen (pretty much most of them except for factor VII).<\/li><\/ul><ul><li><strong>Normal APTT is 30-40s<\/strong>, it can be prolonged if any of the factors are missing or an inhibitor exists, or in warfarin therapy (less likely; typically, the PT is prolonged).<\/li><li>In case of prolongation, a 50:50 mix of the patient&#8217;s plasma together with normal plasma can help to differentiate between a factor deficiency and an inhibitor (if the mix doesn&#8217;t correct the time, it means that an inhibitor is present).<\/li><\/ul><\/li><li><strong>PT (prothrombin time)<\/strong> tests the extrinsic and common pathways.<ul><li>Phospholipids, tissue factor, and calcium are added to citrated plasma<\/li><li>PT measures factors VII, X, V, II, and fibrinogen.<\/li><li><strong>Normal PT is 10-14s<\/strong> but it is typically measured in INR values (normal value is below 1.1; in warfarin therapy, it is typically around 3.0).<\/li><li>A typical cause of prolongation is the usage of warfarin. Typically, patients who use it experience prolonged PT but normal APTT.<\/li><li>The mixing study is applied here as well.<\/li><li>Vitamin K deficiency can also cause PT prolongation as it works similarly to what warfarin does (inhibits vitamin K recycling).<\/li><\/ul><\/li><li><strong>TT (thrombin time)<\/strong> tests the common pathway (fibrin formation).<ul><li>Thrombin is being added to citrated plasma.<\/li><li>TT measures fibrinogen (or the inhibition of thrombin).<\/li><li><strong>Normal TT is 14-16s<\/strong>, it can be prolonged in fibrinogen deficiency, or thrombin inhibitor (heparin).<\/li><\/ul><\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Additionally, essays and techniques for specific clotting factors exist to help quantify them.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Platelet function tests<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<p class=\"wp-block-paragraph\">Platelet aggregometry involves the <strong>PFA-100 test<\/strong>, which measures the aggregation of platelets (and hence their function) when aggregating agents are added to platelets (typically ADP\/collagen).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PFA-100 measurements are prolonged in platelet defects and VW disease.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Nowadays, it is possible to check specific platelet glycoproteins (receptors) using flow cytometry.<\/p>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Description<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Blood count, blood smear smear, and plasma fibrinogen<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Bleeding time<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Coagulation tests (APTT, PT, TT)<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Platelet function tests<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Description Bleeding disorders can stem from abnormalities in: Blood vessels Platelets Coagulation factors Hemostatic test are used for testing the hemostatic system and serve as an important diagnostic tool to help assess the function of the components mentioned above: Blood count Blood smear Plasma fibrinogen Bleeding time Coagulation test (APTT, PT, TT) Platelet function tests [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":4474,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-4635","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Hemostatic tests &#8211; 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