The main methods of laboratory diagnostics of hemorrhagic syndromes

Tests for vascular - platelet factors. Tests for platelet factors include the quantitative platelet count, its morphology, platelet aggregation and adhesiveness tests, bleeding time test, estimation of platelet components in plasma.

Platelet aggregation test. An aggregating agent (activated thrombin, epinephrine, ADP, and collagen) is added to a suspension of platelet rich plasma and the response is measured in a spectrophotometer. Special devices called aggregometers are used to measure platelet aggregation.

Platelet adhesiveness test measures the ability of cells to adhere to glass surface. Adhesiveness can be determined by counting the number of platelet in the anticoagulated blood before they are passed through the column with glass beads, and by counting them again after they have passed through the column.

Bleeding time test measures time required for the cessation of bleeding after a standardized puncture through the skin 3 mm deep. The Duke test involves puncturing the earlobe with a lancet, drops of blood are blotted every 30 second and the time at which bleeding stops is noted. Normal limes for the Duke test are 1 to 3 minutes. The Ivy test have similar procedure but added a blood pressure cuff, which is placed on the upper arm and inflated to 40 mm Hg the skin is pieced with a lancet in the lower forearm. Blood is blotted every 30 second until the bleeding stops. Normal times for the Ivy test are between 2 and 6 minutes.

Tests for plasma factors involved in coagulation and fibrinolisis

Prothrombin time (PT) measures the extrinsic system (factor VII) as well as factors common in both systems (factor X, V, 11 and I). Prothrombin time test is performed by adding tissue extract (factor III = tissue factor) and calcium to the plasma. Normal prothrombin time - 10-17 second.

Activated partial thromboptastin time (APTT or PTTK.) measures the intrinsic system's factors VIII, DC XI and XII, in addition to factors common to both systems. Three substances - phospholipid, a surface activator (Kaolin) and calcium arc added to the plasma. The normal PTTK. is 30-40 seconds.

Fibrinogen determinant test is performed by addition 0,2 ml thromboplastin and 0,1-0,5 % solution of calcium chloride to 1 ml platelet-rich plasma. Formed clot is dried and weighed. The normal fibrinogen levels in the blood are 200 to 400 mg per deciliter of plasma.

Thrombin time or fibrinogen deficiency test is performed by added the activated thrombin to blood plasma and measure the time in takes to form a clot The test reflects fibrinogen-fibrin conversion. Normal thrombin lime - 10-12 second.

Hemorrhagic syndrome

The bleeding disorders are a heterogeneous group of syndromes characterized by easy bruising and spontaneous bleeding from the blood vessels.

Classification:

/. Disorders of coagulation (coagulopathy) - hemophilia.

II. Disorders of platelets (thrombocytopenia) - Werlhoff's disease.

Ill Vascular disorders (vasopathy) Henoch-Schoenlein purpura.

HEMOPHILIA