Medical Laboratory Haematology I: Haemostasis
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Questions and Answers

What is the normal range for platelet count?

150,000 - 400,000 cells/mm3

What does the bleeding time test evaluate?

How fast injured blood vessels in the skin stop bleeding.

What is the maximum normal bleeding time using the Duke method?

  • 3 minutes (correct)
  • 8 minutes
  • 1 minute
  • 15 minutes

    • The bleeding time is prolonged when the platelet count is below _____ cells/µL.

    <p>50,000</p> Signup and view all the answers

    What anticoagulant is commonly used for blood specimen collection in coagulation tests?

    <p>3.2% sodium citrate</p> Signup and view all the answers

    Which factors does the prothrombin time (PT) test evaluate?

    <p>I, II, V, VII, and X</p> Signup and view all the answers

    The Ivy method for bleeding time requires a blood pressure cuff to be inflated.

    <p>True</p> Signup and view all the answers

    What is the IN ext{R} normal value range?

    <p>0.8 - 1.1</p> Signup and view all the answers

    Which condition can prolong the Prothrombin time?

    <p>Vitamin K deficiency</p> Signup and view all the answers

    Prolonged bleeding time is typically considered critical if it lasts longer than _____ minutes.

    <p>15</p> Signup and view all the answers

    What procedure should follow if bleeding continues for more than 15 minutes?

    <p>The procedure should be discontinued and pressure applied to the wound site.</p> Signup and view all the answers

    What does INR stand for?

    <p>International Normalized Ratio</p> Signup and view all the answers

    What is considered an acceptable INR range for a healthy person?

    <p>0.9–1.3</p> Signup and view all the answers

    What does an INR value of 5 or 5.5 indicate?

    <p>Unacceptably high risk of bleeding</p> Signup and view all the answers

    What is the principle of the activated partial thromboplastin time (APTT) test?

    <p>Measures the clotting time of plasma after activating contact factors</p> Signup and view all the answers

    What is the normal aPTT range?

    <p>30 – 40 seconds</p> Signup and view all the answers

    What is thrombin time (TT) used for?

    <p>To measure the time required for thrombin to convert fibrinogen to insoluble fibrin clot</p> Signup and view all the answers

    What are common causes of prolonged TT?

    <p>Hypofibrinogenaemia, raised concentrations of FDP, unfractionated heparin</p> Signup and view all the answers

    What does a mixing study help to distinguish?

    <p>Factor deficiencies from factor inhibitors</p> Signup and view all the answers

    Which factors can cause prolonged aPTT?

    <p>All of the above</p> Signup and view all the answers

    What is a normal range for fibrinogen concentration?

    <p>1.8–3.6 g/l</p> Signup and view all the answers

    What is the method used to perform an individual factor assay based on PT and APTT?

    <p>Using dilutions of standard or reference plasma and test plasma to correct PT or APTT</p> Signup and view all the answers

    What is haemostasis?

    <p>The process of arresting bleeding from an injured blood vessel.</p> Signup and view all the answers

    Which of the following components are involved in haemostasis? (Select all that apply)

    <p>Coagulation factors</p> Signup and view all the answers

    What occurs during the vascular phase after a blood vessel is damaged?

    <p>Vasoconstriction results, reducing blood flow from the injured vessel.</p> Signup and view all the answers

    Platelets adhere to the damaged vessel surface primarily through von Willebrand factor.

    <p>True</p> Signup and view all the answers

    What are the primary mechanisms of normal clotting response? (Select all that apply)

    <p>Platelet plug formation</p> Signup and view all the answers

    What is the role of prostacyclin in haemostasis?

    <p>Prostacyclin inhibits thromboxane formation.</p> Signup and view all the answers

    Haemophilia A is characterized by a deficiency of Factor _____

    <p>VIII</p> Signup and view all the answers

    Thrombocytopenia is defined as an inadequate number of _____

    <p>platelets</p> Signup and view all the answers

    Which factor is deficient in Haemophilia B?

    <p>Factor IX</p> Signup and view all the answers

    What is the main clinical feature of thrombocytopathy?

    <p>Adequate number of platelets but abnormal function.</p> Signup and view all the answers

    Which of the following is a cause of acquired bleeding disorders? (Select all that apply)

    <p>Liver disease</p> Signup and view all the answers

    Inadequate numbers of platelets can lead to thrombotic disorders.

    <p>False</p> Signup and view all the answers

    What is the structure and function of bone marrow?

    <p>Bone marrow is a highly cellular, viscous, and highly vascular tissue that supports the proliferation, differentiation, and maturation of hematopoietic cells.</p> Signup and view all the answers

    Which type of bone marrow contains mainly fat cells?

    <p>Yellow marrow</p> Signup and view all the answers

    The normal volume of red marrow is between 3000 - 4000 mL.

    <p>False</p> Signup and view all the answers

    What does the hemopoietic compartment of bone marrow produce daily?

    <p>Approximately 500 billion blood cells daily.</p> Signup and view all the answers

    What are the major components found in normal bone marrow?

    <p>All of the above</p> Signup and view all the answers

    Bone marrow examination involves analysis of samples obtained through ________ and _______.

    <p>bone marrow aspiration, bone marrow biopsy</p> Signup and view all the answers

    What conditions indicate a bone marrow examination?

    <p>Unexplained anemia, cytopenia or cytosis, abnormal peripheral blood smear morphology, diagnosis, staging and follow-up of hematological malignancies.</p> Signup and view all the answers

    Bone marrow puncture is permitted in patients with coagulopathies.

    <p>False</p> Signup and view all the answers

    What is the best site for bone marrow aspiration in adults?

    <p>Posterior iliac crest</p> Signup and view all the answers

    Match the following types of bone marrow collection with their descriptions:

    <p>Bone marrow aspiration = A procedure to collect a sample of bone marrow fluid. Bone marrow biopsy = A trephine biopsy that yields a solid piece of bone marrow for examination. Clot section = Assessment of cellularity and infiltrative processes. Biopsy imprint smears = Used for cytological examination of bone marrow samples.</p> Signup and view all the answers

    What cells constitute the bone marrow stroma?

    <p>Fibroblasts, macrophages, adipocytes, osteoblasts, osteoclasts, endothelial cells.</p> Signup and view all the answers

    What is the defining characteristic of Reed-Sternberg cells?

    <p>Large lobulated or multi-nucleate cells</p> Signup and view all the answers

    Which stage of Hodgkin lymphoma indicates involvement of lymph nodes on both sides of the diaphragm?

    <p>Stage III</p> Signup and view all the answers

    What is the 5-year survival rate for Stage II Hodgkin lymphoma?

    <p>85%</p> Signup and view all the answers

    Burkitt’s lymphoma is associated with chronic malaria and EBV in equatorial Africa.

    <p>True</p> Signup and view all the answers

    What translocation is commonly associated with Burkitt’s lymphoma?

    <p>t(8;14)</p> Signup and view all the answers

    The most common type of non-Hodgkin lymphoma is _____.

    <p>DLBCL</p> Signup and view all the answers

    What proteins are characteristic of DLBCL?

    <p>Positive for CD20</p> Signup and view all the answers

    What is the treatment regimen typically used for DLBCL?

    <p>R-CHOP</p> Signup and view all the answers

    What is the hallmark feature of sickle cell anemia?

    <p>Sickle-shaped red blood cells</p> Signup and view all the answers

    Which of the following methods can diagnose haemoglobinopathies?

    <p>All of the above</p> Signup and view all the answers

    Study Notes

    Haemostasis Overview

    • Haemostasis is the process of stopping bleeding from injured blood vessels.
    • Key components involved: blood vessels, platelets, coagulation factors, and inhibitors.
    • Normal clotting response includes vasoconstriction, platelet plug formation, and fibrin clot formation followed by fibrinolysis.

    Phases of Haemostasis

    • Vascular Phase: Injury triggers vasoconstriction, reducing blood flow through sympathetic reflex and release of vasoconstrictors like TXA2 and serotonin.
    • Platelet Phase: Platelets adhere to damaged vessel surfaces, swell, and activate, forming a temporary plug through adhesion, activation, and aggregation.
    • Coagulation Phase: Activation of clotting cascades leads to the conversion of fibrinogen to fibrin, creating a stable secondary haemostatic plug.

    The Coagulation Cascade

    • Two pathways involved: extrinsic (initiated by tissue factor and FVIIa) and intrinsic (activated by factors within the blood).
    • The classical cascade model does not account for certain deficiencies or essential components like calcium and phospholipids.

    Disorders of Haemostasis

    • Bleeding Disorders: Can arise from vessel defects, platelet disorders, or factor deficiencies.
    • Vessel Defects: Conditions like Vitamin C deficiency or infections that compromise vascular integrity.
    • Platelet Disorders:
      • Thrombocytopenia: inadequate platelet numbers due to drug-induced causes or bone marrow failure.
      • Thrombocytopathy: functional defects of platelets despite normal numbers, seen in conditions like uraemia.

    Factors Affecting Haemostasis

    • Factor deficiencies, including Hemophilia A (deficiency of Factor VIII) and Hemophilia B (Factor IX deficiency).
    • von Willebrand’s disease is characterized by reduced levels or dysfunction of von Willebrand factor.

    Acquired Bleeding Disorders

    • Conditions like liver disease, Vitamin K deficiency, and the effect of anticoagulants such as warfarin or heparin.

    Investigation of Bleeding Disorders

    • Complete Blood Count (CBC): Essential for evaluating platelet count and overall blood health.
    • Bleeding Time (BT): Measures the time for vessels to constrict post-injury, providing insight into platelet function.
    • Screening Tests:
      • Prothrombin Time (PT)
      • Activated Partial Thromboplastin Time (APTT)
      • Thrombin Time (TT)
      • Fibrinogen concentration assays.

    Clinical Features of Bleeding Disorders

    • Different bleeding sites based on disorder type: superficial (skin, mucous membranes) versus deep tissue (joints, muscles).
    • Common signs include petechiae for platelet disorders and larger hematomas for coagulation factor disorders.

    Conclusions

    • Understanding of haemostasis is crucial for diagnosing disorders.
    • Evaluation involves a series of tests to assess primary and secondary haemostasis efficiently.### Bleeding Time Overview
    • Bleeding time reflects the efficiency of tissue fluid, capillary function, and platelet count/plug formation capability.
    • Prolonged bleeding times can indicate a platelet count below 50,000/µL and dysfunction in platelets.
    • Tests for bleeding disorders include PT (Prothrombin Time), APTT (Activated Partial Thromboplastin Time), PLT (Platelet count), and Fibrinogen levels.

    Indications for Bleeding Time Testing

    • A history of frequent or spontaneous bleeding.
    • Assessment required prior to any surgery or biopsy.
    • Monitoring patients during anticoagulant treatment.
    • Family history of bleeding disorders is significant.

    Methods of Measuring Bleeding Time

    • Duke Method: Less than 3 minutes; standardized ear lobe puncture with blotting every 30 seconds, noted for ease but low precision.
    • Ivy Method: Less than 8 minutes; uses a blood pressure cuff at 40 mm Hg for standardization and sensitivity, but may yield low results due to technique variability.
    • Mielke Method: A modification of the Ivy method utilizing a controlled blade incision with precise depth, which better resembles surgical conditions.
    • Simplate/Surgicutt Method: Most preferred; utilizes a spring-activated device for a controlled and standardized incision depth, although slight scarring may occur.

    Normal and Prolonged Bleeding Times

    • Normal bleeding time is 1 to 9 minutes.
    • Platelet dysfunction indicated by a bleeding time of 9 to 15 minutes.
    • Critical results (greater than 15 minutes) require immediate management, and pressure should be applied.

    Apparatus and Procedure Essentials

    • Essential apparatus includes a sterile lancet, filter paper, and a stopwatch.
    • Significant precautions include ensuring the patient has not taken aspirin or blood thinners within 7 to 10 days, as this may falsify results.

    Detailed Procedure for Simplate/Surgicutt Method

    • Select a puncture site on the forearm free of visible veins.
    • Clean the site using alcohol pads and allow to dry.
    • Inflate a blood pressure cuff to 40 mm Hg.
    • Perform puncture and start timing; blot blood at 30-second intervals until bleeding stops.
    • If bleeding persists beyond 15 minutes, apply pressure and record results as greater than 15 minutes.

    Important Considerations in Results Interpretation

    • Sources of error include improper puncture technique, residual alcohol on the skin, and inconsistency in incision direction.
    • Prolonged bleeding time can result from conditions such as thrombocytopenia and von Willebrand's disease.

    Whole Blood Clotting Time (CT)

    • Refers to the time until fibrin threads form after blood enters a capillary tube.
    • Normal range for CT is 3 to 6 minutes.

    Screening Tests for Blood Coagulation

    • Include Prothrombin Time (PT), Activated Partial Thromboplastin Time (APTT), thrombin time (TT), and fibrinogen concentration.

    Prothrombin Time (PT)

    • Measures the time for recalcified plasma to clot after adding thromboplastin and calcium; sensitive to factors I, II, V, VII, and X.
    • Normal PT range is 11-16 seconds; results expressed as a prothrombin ratio or INR.

    Activated Partial Thromboplastin Time (APTT)

    • Evaluates intrinsic path efficacy; sensitive to factors VIII, IX, X, V, prothrombin, and fibrinogen.
    • Protocol involves incubating plasma with activators, then adding phospholipids and calcium to measure clotting time.

    Specimen Collection and Processing

    • Blood collection via venepuncture using 3.2% sodium citrate as an anticoagulant.
    • Centrifugation yields platelet-poor plasma for testing; proper handling and timing critical to avoid degradation of test effectiveness.

    Freezing and Storage of Plasma Samples

    • Samples can be frozen at -70°C for future testing; avoid thawing before APTT determinations due to potential interference.### APTT Results and Interpretation
    • APTT is performed to assess the intrinsic and common pathways of blood coagulation.
    • Normal APTT range: 30 – 40 seconds.
    • Prolonged APTT with normal PT indicates possible deficiencies in factors VIII, IX, XI, XII, or the presence of an inhibitor.

    Causes of Prolonged APTT

    • Conditions like Haemophilia A and B cause intrinsic pathway deficiencies.
    • Coagulation inhibitors and DIC can lead to prolonged APTT.
    • Liver disease also impacts coagulation factors.

    Critical Limits of APTT

    • APTT slightly lengthened in young individuals and shortened in older populations.
    • Premature infants show prolonged APTT, normalizing by 6 months.
    • Factors such as lipemia and hyperbilirubinemia can interfere with APTT testing.

    Thrombin Time (TT)

    • Measures clotting time after thrombin is added to plasma.
    • TT primarily detects fibrinogen level abnormalities.
    • Affected by abnormal fibrinogen levels, dysfibrinogenemia, and antithrombin presence.

    Thrombin Time Procedure

    • Begins with warming saline and adding patient plasma with bovine thrombin.
    • Recording starts when thrombin is added and stops upon visible clot formation.
    • Mixing studies may follow prolonged TT outcomes to identify deficiencies or inhibitors.

    Causes of Prolonged TT

    • Hypofibrinogenemia or liver disease can elevate TT.
    • Severe prolongation often due to unfractionated heparin or abnormal fibrinogen function.

    Mixing Studies

    • Conducted with patient plasma mixed with normal plasma to determine factor deficiencies or inhibitors.
    • Correction indicates factor deficiency; failure suggests inhibitors present.

    Confirmatory Tests

    • Reptilase time, mixing tests, and fibrinogen assays are used for further evaluation.

    Fibrinogen Measurement

    • Fibrinogen assay is based on clotting diluted plasma with thrombin.
    • Calibration curves are essential, normal fibrinogen range: 1.8–3.6 g/L.
    • Low levels may indicate hypofibrinogenemia, DIC, or liver disease.

    Bone Marrow Overview

    • Bone marrow is highly vascular tissue responsible for haematopoiesis (blood cell generation).
    • Two types: Red Marrow (haematopoietic tissue) and Yellow Marrow (fat tissue).
    • Active red marrow found in flat bones and ends of long bones; yellow in medullary cavities.

    Normal Bone Marrow Composition

    • Contains haematopoietic cells, vascular sinusoids, fibroblasts, macrophages, and fat cells.
    • Represents about 4% of body mass in adults.

    Sites and Techniques for Bone Marrow Examination

    • Aspirations typically performed in the posterior iliac crest or sternum depending on age.
    • Procedures include aspiration, biopsy, and analysis using various microscopic and flow cytometry techniques.

    Functions of Bone Marrow

    • Produces red blood cells, white blood cells, and platelets essential for oxygen transport and immune function.

    Applications of Bone Marrow Examination

    • Essential for diagnosing hematologic and non-hematologic conditions.
    • Used for monitoring patients undergoing chemotherapy or with suspected malignancies.

    Cellular Analysis of Bone Marrow

    • Evaluation typically includes semi-quantitative and qualitative assessments of hematopoietic activity.
    • Recent techniques include culture for cytogenetic studies, electron microscopy, and other advanced methodologies.

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