Anaemia Flashcards
What are the stages of red blood cell maturation in the bone marrow?
Red blood cell maturation in the bone marrow involves several stages. Initially, the erythrocytes are large, nucleated, and have intensely blue-staining cytoplasm. As they mature, they become smaller, lose their nucleus, and contain a higher proportion of hemoglobin, imparting a redder coloration. The penultimate stage is the reticulocyte, which undergoes remodeling of its cell surface before exiting the bone marrow.
Describe the significance of reticulocytes in the bloodstream.
Reticulocytes are juvenile red cells that contain varying degrees of residual RNA, which is absent in mature erythrocytes. The presence of reticulocytes in peripheral blood indicates ongoing erythropoiesis, and their volume can indicate accelerated red cell regeneration. In dogs, aggregate reticulocytes are observed, while in cats, there is an additional “teenage” stage called punctate reticulocytes.
Explain the oxygen-hemoglobin dissociation curve and its significance in oxygen transport.
The oxygen-hemoglobin dissociation curve illustrates the saturation of hemoglobin with oxygen concerning the partial pressure of oxygen in arterial blood. It demonstrates the cooperative binding of oxygen to hemoglobin. In systemic capillaries, where oxygen levels are low, hemoglobin releases oxygen readily to oxygenate tissues. In the lungs, where oxygen levels are high, hemoglobin binds oxygen rapidly. The curve plateaus when all heme sites are fully oxygenated, and the steep incline represents increased oxygen affinity as successive oxygen molecules bind.
What is the role of 2-3 diphosphoglyceric acid (DPG) in oxygen transport?
2-3 DPG is necessary for the release of oxygen when partial pressure is low, such as in the systemic capillaries supplying blood to the tissues. Its levels are important during storage of red cells, as they decrease, making oxygen release less efficient. However, within 24 hours of transfusion, the recipient’s body restores normal 2-3 DPG levels, improving oxygen delivery.
How are senescent erythrocytes cleared from the bloodstream, and what happens to their components?
Senescent erythrocytes are primarily phagocytosed by Kupffer cells in the liver and red pulp macrophages in the spleen. During clearance, some red cell components are recycled. Globulin is broken down into amino acids, and heme is separated into iron and biliverdin. Iron can be stored or transported in plasma to be stored in the liver for erythropoiesis. Biliverdin is converted to bilirubin, which is excreted in the feces after conjugation in the liver. (Senescent cells are unique in that they eventually stop multiplying but don’t die off when they should. They instead remain and continue to release chemicals that can trigger inflammation)
What are the main methods used by in-house hematology analyzers to analyze blood components?
In-house hematology analyzers use various methods to analyze blood components. These include:
Quantitative Buffy Coat Analysis (QBC): Centrifugation of a dye-coated microhematocrit tube to calculate cell count based on the width and fluorescence of different cell layers.
Impedance Counters: Passing blood cells through an electrical current, with impedance changes used to differentiate cell types based on size.
Laser Flow Cytometry: Cells pass through a laser beam, and interruptions in light help count and characterize cells, with additional staining for more accurate identification.
What components are typically included in the analysis of the erythron by hematology analyzers?
The analysis of the erythron by hematology analyzers includes:
Red Cell Mass
Red Cell Indices:
Mean Cell Volume (MCV)
Mean Cell Hemoglobin (MCH)
Mean Cell Hemoglobin Concentration (MCHC)
Red Cell Distribution Width (RDW)
Reticulocyte Count
Explain the significance of Mean Cell Volume (MCV) and Mean Cell Hemoglobin Concentration (MCHC) in red cell analysis.
MCV (Mean Cell Volume): It represents the average volume of erythrocytes. An increased MCV indicates larger cells (macrocytes), while a decreased MCV indicates smaller cells (microcytes).
MCHC (Mean Cell Hemoglobin Concentration): It represents the average hemoglobin concentration in erythrocytes. Normal MCHC is termed normochromic, low MCHC is hypochromic, and high MCHC is considered an artifact.
What does an increased Red Cell Distribution Width (RDW) indicate?
An increased RDW indicates a greater variation in the size of red cells, a condition known as anisocytosis. This is consistent with a regenerative response, as immature red cells tend to be larger in size.
How can the Dot Plot in graphical results be useful in analyzing blood samples?
The Dot Plot in graphical results is created from data about individual red cells. It provides a visual representation of cell fluorescence (RNA volume) on the x-axis and cell size on the y-axis. Changes in the reticulocyte count are often easier to identify on the Dot Plot. Large populations of cells outside the normal area may indicate abnormal cell morphology, prompting further evaluation of a blood smear.
What are some limitations of hematology analyzers?
Sample Quality: Poor sample quality, including lipemia, hemolysis, clots, or using aged samples, can affect accuracy.
Cell Clumping: Agglutinated erythrocytes or platelet clumps can reduce cell counts inaccurately.
Standard Cell References: Red cells that deviate from the standard reference range may be misidentified, especially if they are larger, smaller, or nucleated.
Quality Control: Regular maintenance and quality control testing are essential to ensure optimal analyzer performance.
Why is it recommended to evaluate a blood smear even if automated results are available?
While automated hematology analyzers provide valuable information, an overreliance on them alone can lead to missing vital erythrocyte information. Evaluating a blood smear is recommended to confirm the accuracy of automated results, especially when abnormalities are suspected based on graphical displays or clinical context.
What are the key steps and precautions in blood sample procurement?
Aspirate blood carefully to avoid damage to erythrocytes.
Use veins, not capillaries, to ensure parasite detection.
Fill EDTA tubes to the specified line.
Remove the needle to prevent unintentional cell damage.
Avoid touching the tube’s sides.
Mix the sample thoroughly.
Wear gloves when handling blood samples.
Label tubes properly.
What are the steps involved in making a blood smear?
Prepare a flat surface with the frosted side of the slide facing up.
Place a small drop of blood at one end using a plain capillary tube.
Hold a second clean slide at a 30-45 degree angle.
Slowly pull the spreader slide towards the blood drop until it touches.
Allow the blood to spread 75% of the slide’s width.
Quickly and smoothly push the slide away from the drop.
Dry the smear quickly to prevent osmotic changes.
Label the slide with the patient’s name and date.
What are the different regions of a blood smear, and what can be observed in each region?
Feathered Edge: Large cells, microfilaria (parasites), and platelet clumps. Morphology and distribution may be abnormal.
Monolayer: Evenly distributed cells, suitable for cell count. Used with an oil immersion lens.
The Body: Examined for rouleaux, agglutination, or other clumps using a low-power lens.
The ‘Dot End’: Morphology may be poor.
Describe the normal characteristics of erythrocytes in terms of shape, color, and size.
Shape: Biconcave disc, allowing for easy movement through capillaries.
Color: Red, with a central area of pallor representing the less dense center. Cats may lack a prominent central pallor. Normal coloration is termed normochromic.
Size: Dogs have erythrocytes around 7 microns, while cats have 5.5-6.5 microns. Normal size is termed normocytic.
Explain the abnormalities related to erythrocyte size, including hypochromasia, polychromasia, and macrocytosis
Hypochromasia: Erythrocytes lack color, appearing like a bike wheel, indicating iron deficiency and chronic blood loss. Often smaller in size, reported as low MCHC.
Polychromasia: Variation in erythrocyte color, indicating regenerative response with larger, bluer cells. May include reticulocytes, identifiable with stains like New Methylene Blue.
Macrocytosis: Increased number of larger erythrocytes, often associated with early release of immature cells from the bone marrow. May stain bluer.
What are spherocytes, and what pathology are they indicative of?
Spherocytes: Small, spherical, intensely staining red blood cells.
Indicative of: Pathognomonic for Immune-Mediated Hemolytic Anemia (IMHA). Formed following a failed phagocytic encounter.
