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?
The bleeding time is prolonged when the platelet count is below _____ cells/µL.
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What anticoagulant is commonly used for blood specimen collection in coagulation tests?
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Which factors does the prothrombin time (PT) test evaluate?
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The Ivy method for bleeding time requires a blood pressure cuff to be inflated.
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What is the IN ext{R} normal value range?
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Which condition can prolong the Prothrombin time?
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Prolonged bleeding time is typically considered critical if it lasts longer than _____ minutes.
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What procedure should follow if bleeding continues for more than 15 minutes?
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What does INR stand for?
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What is considered an acceptable INR range for a healthy person?
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What does an INR value of 5 or 5.5 indicate?
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What is the principle of the activated partial thromboplastin time (APTT) test?
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What is the normal aPTT range?
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What is thrombin time (TT) used for?
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What are common causes of prolonged TT?
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What does a mixing study help to distinguish?
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Which factors can cause prolonged aPTT?
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What is a normal range for fibrinogen concentration?
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What is the method used to perform an individual factor assay based on PT and APTT?
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What is haemostasis?
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Which of the following components are involved in haemostasis? (Select all that apply)
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What occurs during the vascular phase after a blood vessel is damaged?
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Platelets adhere to the damaged vessel surface primarily through von Willebrand factor.
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What are the primary mechanisms of normal clotting response? (Select all that apply)
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What is the role of prostacyclin in haemostasis?
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Haemophilia A is characterized by a deficiency of Factor _____
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Thrombocytopenia is defined as an inadequate number of _____
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Which factor is deficient in Haemophilia B?
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What is the main clinical feature of thrombocytopathy?
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Which of the following is a cause of acquired bleeding disorders? (Select all that apply)
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Inadequate numbers of platelets can lead to thrombotic disorders.
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What is the structure and function of bone marrow?
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Which type of bone marrow contains mainly fat cells?
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The normal volume of red marrow is between 3000 - 4000 mL.
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What does the hemopoietic compartment of bone marrow produce daily?
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What are the major components found in normal bone marrow?
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Bone marrow examination involves analysis of samples obtained through ________ and _______.
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What conditions indicate a bone marrow examination?
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Bone marrow puncture is permitted in patients with coagulopathies.
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What is the best site for bone marrow aspiration in adults?
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Match the following types of bone marrow collection with their descriptions:
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What cells constitute the bone marrow stroma?
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What is the defining characteristic of Reed-Sternberg cells?
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Which stage of Hodgkin lymphoma indicates involvement of lymph nodes on both sides of the diaphragm?
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What is the 5-year survival rate for Stage II Hodgkin lymphoma?
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Burkitt’s lymphoma is associated with chronic malaria and EBV in equatorial Africa.
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What translocation is commonly associated with Burkitt’s lymphoma?
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The most common type of non-Hodgkin lymphoma is _____.
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What proteins are characteristic of DLBCL?
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What is the treatment regimen typically used for DLBCL?
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What is the hallmark feature of sickle cell anemia?
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Which of the following methods can diagnose haemoglobinopathies?
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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.
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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.
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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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Description
This quiz focuses on the essential concepts of haemostasis and its disorders, aimed at students of Medical Laboratory Haematology I. You will explore the main components involved in haemostasis, including the roles of blood vessels, platelets, and coagulation factors.
