University:
College
Course:
Medical Laboratory Science
Academic year:

2023
Views:

192

Pages:

1
Author:

Carlo M.

HEMATOLOGY LABORATORY • BLOOD CLOT RETRACTION OUTLINE • Blood Clot Retraction o Methods o Clinical Significance LABORATORY EVALUATION OF PRIMARY HEMOSTASIS: BLOOD CLOT RETRACTION • • • • When blood coagulation is complete, the clot normally undergoes retraction (serum is expressed from the clot and the clot becomes denser). In normal clot retraction requires a normal number of functioning platelets, calcium, ATP, and a normal fibrinogen and fibrin. An abnormal clot retraction time is found in Glanzmann’s thrombasthenia and thrombocytopenia. In dysfibrinogenemia/ hypofibrinogenemia, the formed clot will be small and there will be increased amounts of red blood cells expressed from the clot. (RBC fall out) Clot retraction may also be abnormal in paraproteinemias, where the protein interferes with fibrin formation. In DIC, the formed clot will appear small and ragged, and increased RBC fall out. In blood containing high red blood cells count, the degree of retraction is limited became of the large volume of RBC within the clot. In anemia states, the reverse occurs and the degree of clot retraction is increased. METHODS • • Single Tube Method Hirshboeck method/Castor Oil method • SINGLE TUBE METHOD • • Procedure 1. Place 5 ml venous blood in a clean dry centrifuge tube. 2. Insert a coiled wire in the bottom of the tube (1 mm thick, with a cm diameter coil) 3. Incubate at 37oc for 1 hour after clotting has occurred. 4. Gently lift the wire and allow the attached clot to drain for 2 minutes. 5. Read the volume of fluid remaining in the tube. Expressed this volume as a percentage of the original volume of the whole blood placed in the tube. Reference Range: 44 – 67% Color and Character of the Serum: o Normally, a clear pale yellow serum appears within the first hour. In 18- 24 hours, the volume varies from 40% to 57% of the total amount of blood. o When the clot is defective ad incapable of proper retraction, the volume of serum is less than 40%. o Serum may appear milky after meals or in diabetes and leukemia. o It may be deep yellow in haemolytic jaundice leukemia. o It may be deep yellow in haemolytic jaundice, in obstructive jaundice or in carotenemia. HIRSHBOECK METHOD • • Materials: Castor oil and WBC diluting pipette Procedure o Puncture sterilized finger, wipe off first drop, suck 20 ml of blood in a Sahli’s pipette. o Slowly, allow the blood to flow down the pipette until a big drop accumulates at the tip. o Slowly lower the pipette until the drop of blood touches the castor oil, and allow the blood to be suspended just below the meniscus. o Start the timing and observe for a visible dimpling or a nipple-like protrusion on the surface of the drop of blood. Note the time. This indicates the end front of the test. Note: clot retraction is reported delayed if dimpling happens after 1 hour. Record the time. CLINICAL SIGNIFICANCE • • Platelet disorders (Glanzmann’s thrombasthenia) and thrombocytopenia.