1. Hematology 425 Anemias: RBC Morphology & Approach to Diagnosis
Russ Morrison
October 18, 2006
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2. Approach to Diagnosis of Anemia
RBCs serve to transport oxygen to the tissues
A decrease in the ability to deliver sufficient oxygen results in hypoxia
Anemia is the consequence of decreased oxygen-carrying capacity of the blood and the resultant tissue hypoxia
Anemia is not a disease, but a manifestation of underlying disease
Anemia is the most common manifestation of disease worldwide
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3. Approach to Diagnosis of Anemia
Anemia is defined as a reduction of more than 10% from the normal value for RBC count, Hgb concentration and RBC mass for a patient
In practice, a reduction in RBCs, Hgb and Hct compared to “normal” for healthy persons of the same age, gender, race and environmental conditions is cause for investigation
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4. Approach to Diagnosis of Anemia
Clinical diagnosis of anemia is made from the history, physical examination, signs, symptoms, hematologic values and other findings.
Diagnosis begins with a history and physical examination
The history should include questions relating to diet, drug ingestion, chemical exposure, travel, bleeding history, etc.
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5. Approach to Diagnosis of Anemia
Family history should include ethnicity, bleeding disorders and diseases that produce anemia.
Physical exam should include skin (jaundice, pallor, petechiae), eyes (hemorrhage, jaundice), mucosal bleeding, sternal tenderness, lymphadenopathy, splenomegaly, hepatomegaly, etc.
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6. Approach to Diagnosis of Anemia
Pallor of the conjunctiva and nail beds, dyspnea, vertigo, headache, muscle weakness, lethargy and other symptoms may be present in moderate anemia.
Severe anemias produce tachycardia, hypotension and other symptoms in addition to those listed for moderate anemia.
Severity of anemia is based on degree of reduction of blood volume, cardiopulmonary adaptation and speed of progression of the anemia.
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7. Laboratory Diagnosis of Anemia
A complete CBC is performed for the patient who is suspected of having anemia
Includes RBCs, Hgb, Hct, RBC indices, WBCs and Platelet count
RBC indices determine mean corpuscular size (MCV), mean corpscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC), with the most important being MCV
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8. Laboratory Diagnosis of Anemia
The CBC may also include a RBC histogram and RDW for additional clues in the diagnosis.
The RDW represents variation within the volume or size distribution of the RBCs
A reticulocyte count should be performed for every patient suspected of having anemia
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9. Laboratory Diagnosis of Anemia
Reticulocyte Count
The reticulocyte count permits effective assessment of RBC production by the BM
The reticulocyte count classifies the anemia as hypoproliferative (< 2% retics) or hyperproliferative (> 2% retics) – indicates if the BM is producing adequate RBCs for the anemia
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10. Laboratory Diagnosis of Anemia
THE MOST IMPORTANT EXAMINATION IN THE WORK-UP OF ANEMIA IS THE EXAMINATION OF THE PB SMEAR
Careful consideration is given to RBC variation in size, shape, color content and inclusions
The PB smear serves as a quality control to validate the results from the automated hematology analyzer
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11. Laboratory Diagnosis of Anemia
PB Smear
Size of RBCs (should be uniform)
NL RBCs, um
Microcytic RBCs, < 6 um
Macrocytic > 9 um
Shape and appearance of RBCs should be noted
Parasites and RBC inclusions may be observed
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12. Laboratory Diagnosis of Anemia
PB Smear
WBC differential may provide information useful to the diagnosis of anemia
Hypersegmented PMNs
Blast cells
Early or abnormal granulocytes
Reactive lymphocytes
May all be clues to the anemic state
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13. Laboratory Diagnosis of Anemia
PB Smear
Adequacy of number of platelets should be estimated
Hematologic values in adults with anemia are presented in the following slide
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14. Laboratory Diagnosis of Anemia
Test
Men
Women
RBC (x1012/L)
< 4.6
< 4.0
Hgb (g/dL)
< 14.0
< 12.0
Hct (%)
< 42
< 35
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15. Laboratory Diagnosis of Anemia
Test
Both Sexes
MCV (fL)
<80 or >94
MCH (pg)
<26 or >32
MCHC (g/dL)
< 32 to 36
RDW
> 15%
Platelets
variable
Reticulocyte, relative
<0.5 or > 1.5 %
Reticulocyte, absolute
< 25 or > 90 x 109/L
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16. Bone Marrow Examination
May be indicated for unexplained anemia associated with cytopenia, cellular excess, fever of unknown origin or suspected malignancy
Reveals morphologic patterns of RBCs and WBCs, the presence of megakaryocytes, the myeloid-to-erythroid ratio and allows special stains to be performed
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17. Other Laboratory Tests
Additional testing may include a urinalysis with microscopic exam, fecal analysis with blood test and testing for parasites
After the anemia is classified morphologically, additional tests may be indicated based on the morphology
Fe, TIBC, ferritin for microcytic, hypochromic anemia
B12, folate for macrocytic, megaloblastic anemia
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18. Treatment of Anemia
Once the pathophysiologic cause of the anemia is determined, treatment may be made available; including
Replacement therapy, such as iron for iron deficiency anemia OR
Supportive therapy, such as transfusion
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19. Mechanisms of Anemia RBC circulating life span is 120 days
The normal, health person loses 1% of the senescent circulating RBCs each day
The BM replaces the lost cells in equilibrium as long as:
Stem cells function appropriately to to mature erythroid precursor cells and release RBCs into the PB
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20. Mechanisms of Anemia
RBC production requires several nutritional factors if production is to remain adequate (B12, folic acid, iron)
Hgb synthesis must also function normally and contribute the the continual production of new RBCs
To maintain a stable hematocrit, production of new RBCs must equal the number of RBCs lost
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21. Erythropoiesis
Normally occurs in the bone marrow with the resulting formation of an adequate total number of RBCs
In anemia, erythropoiesis does not provide adequate numbers of mature RBCs
Ineffective erythropoiesis – RBC production by progenitor cells is defective to the point that cells are destroyed prior to or shortly after leaving the marrow (megaloblastic anemia, thalassemia, sideroblastic anemia)
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22. Erythropoiesis
Insufficient erythropoiesis is associated with a lack of erythroid precursors in the marrow. Normal cellular elements are replaced by fat resulting in hypoplastic (or aplastic) anemia.
Infiltration or replacement of marrow by abnormal cells has also been associated with anemia.
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23. Classification of Anemias
Two common methods of classification of anemia are morphologic and pathophysiologic.
In the morphologic classification, anemia is subdivided into three groups according to blood counts, cell indices (MCV), reticulocyte count, and examination of RBCs on a blood smear:
Normochromic, normocytic
Microcytic, hypochromic
Macrocytic
Fig 16-2 shows classification based on MCV, fig 16-4 shows classification based on RDW
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24. Classification of Anemias
Pathophysiologic classification of anemia relates the disease process to the current concept of causal mechanisms of anemia.
Loss of blood
Excessive destruction of mature erythrocytes
Impaired production of erythrocytes
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25. Morphologic Classification
Normocytic, normochromic anemia has a normal MCV, MCH and MCHC (after ruling out a bi-modal population of RBCs)
Reticulocytes may be normal, increased or decreased
Caused by hemolysis, acute bleeding, malignancy, splenomegaly, toxicity (drugs, radiation) infections, etc.
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26. Morphologic Classification
Microcytic, hypochromic anemia, MCV < 80 fL, MCHC < 32 g/dL
Small cells that have increased central pallor
Caused by abnormal Hgb synthesis, Fe deficiency, chronic disease states
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27. Morphologic Classification
Macrocytic, normochromic anemia, MCV > 94 fL, MCHC >32 g/dL
Large cells with normal central pallor
May be classified as megaloblastic or nonmegaloblastic
Megaloblastic causes are b12 and folate deficiency
Megaloblastic anemia characterized by oval macrocytes and teardrop-shaped cells in PB and megaloblasts or large nucleated RBC precursors in the BM with nuclear maturation lagging behind cytoplasmic development
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28. Morphologic Classification
Nonmegaloblastic anemia also has large RBCs thart are mostly round, but the BM nucleated RBCs do not display megaloblastic maturation changes
Nonmegaloblastic causes are chronic liver disease, chronic hemolytic anemia with a high retic count,, myelodysplastic refractory anemia and other types of anemia
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29. Classification by RDW
Classification based on MCV (normocytic, microcytic and macrocytic) may be subdivided based on RDW
This clasification helps to narrow the diagnostic possibilities relating to the underlying cause of the anemia
See table 16-4
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30. Pathophysiologic Classification of Anemia
Relates disease processes to asociated causes and currently described mechanisms that lead to anemia
See box 16-1
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31. Physiologic Adaptation to Anemia
The body appears to adapt to slowly developing anemia
Decreased oxygen-carrying capacity is compensated by increased heart rate and increased respiration as well as cardiac output
With tissue hypoxia, w,e-BPG increases leading to a decreased oxygen affinity of hemoglobin which, in turn, results in increased delivery of oxygen to tissues
This may lead to relatively asymptomatic patients with very low levels of Hgb
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32. PB RBC Abnormalities Associated with Anemia
May include anisocytosis, poikilocytosis and RBC inclusions
Anisocytosis is abnormal variation in RBC size (reflected by the RDW)
Poikilocytosis is abnormal shape variation of the RBCs
RBC inclusions are material(s) visible in the stained PB smear
Aniso- and poikilocytosis are quantitated and reported when present as 1+,2+.3+
RBC inclusions are reported when observed
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33. Basophilic Stippling
Basophilic stippling appears as round, dark-blue granules in red blood cells on smears stained with supra vital stains such as brilliant cresyl blue. They may be observed in lead poisoning, exposure to some drugs, severe burns, anemias, or septicemia. The granules are precipitated ribosomes and mitochondria.
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34. Howell-Jolly Bodies
Howell-Jolly bodies are spherical blue-black inclusions of red blood cells seen on Wright-stained smears. They are nuclear fragments of condensed DNA, 1 to 2 µm in diameter, normally removed by the spleen. They are seen in severe hemolytic anemias, in patients with dysfunctional spleens or after splenectomy.
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35. Papenheimer Bodies
Pappenheimer bodies are iron containing granules in red blood cells that are seen because the iron is aggregated with mitochondria and ribosomes. They appear as faint violet or magenta specks, often in small clusters, due to staining of the associated protein. They are associated with severe anemias and thalassemias.
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36. Polychromasia
Polychromatophilia may be defined as increased numbers of immature peripheral red blood cells that have a blue-gray tint on Wright-stained smears, indicating the presence of cytoplasmic RNA. These cells are usually larger than normal. Many of these cells prove to be reticulocytes when stained with supravital stains such as brilliant cresyl blue. They appear under conditions of accelerated red cell production.
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37. Rouleaux
Rouleaux formation occurs when red blood cells form stacks or rolls. This is due to either an artifact (such as a result of not preparing the blood smear soon enough after placing the blood on the slide), or it may be due to the presence of high concentrations of abnormal globulins or fibrinogen. This formation of the red blood cells is found in multiple myeloma and macroglobulinemia.
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38. Echinocyte (burr cell)
Echinocytes are red blood cells with many blunt spicules, resulting from faulty drying of the blood smear or from exposure to hyperosmotic solutions. Pathological forms are associated with uremia. Echinocytes contain adequate hemoglobin and the spiny knobs are regularly dispersed over the cell surface, unlike those of acanthocytes.
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39. Elliptocytes
Elliptocytes are red blood cells that are oval or cigar shaped. They may be found in various anemias, but are found in large amounts in hereditary elliptocytosis.
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40. Schistocyte
Schistocytes are red blood cell fragments that result from membrane damage encountered during passage through vessels. They occur in microangiopathic hemolytic anemia, severe burns, uremia, and hemolytic anemias cause by physical agents, as in disseminated intravascular coagulation (DIC). They are sometimes referred to as "bite cells".
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41. Sickle Cell
Sickle cells are red blood cells that have become crescent shaped. When a person with sickle cell anemia is exposed to dehydration, infection, or low oxygen supply, their fragile red blood cells form liquid crystals and assume a crescent shape causing red cell destruction and thickening of the blood. Since the life span of the red blood cell is shortened, there is a temporary depression of red cell production in the bone marrow, and a subsequent fall in hemoglobin (and therefore the resultant anemia).
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42. Stomatocyte
Stomatocytes are red blood cells with an oval or rectangular area of central pallor, sometimes referred to as a "mouth". These cells have lost the indentation on one side and may be found in liver disease, electrolyte imbalance, and hereditary stomatocytosis.
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43. Target Cell
Target cells (codocytes) are erythrocytes with a central color spot in the area of pallor, resembling a target. They are seen in many hemolytic anemias, especially sickle cell, HbC disease, and thalassemia.
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44. Teardrop Cell
Teardrop shaped red blood cells are found in myelofibrosis and other myeloproliferative disorders, pernicious anemia, thalassemia, myeloid metaplasia, and some hemolytic anemias.
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45. Spherocyte
Spherocytes are red blood cells that are almost spherical in shape. They have no area of central pallor like a normal red blood cell. Large spherocytes (macrospherocytes) are seen in hemolytic anemia. Small spherocytes (microspherocytes) are sometimes seen in severe burn cases. A variety of spherical forms are seen in hereditary spherocytosis. The cells depicted in this image are from a patient with hereditary spherocytosis
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46. Acanthocyte
Acanthocytes are red blood cells with irregularly spaced projections. These projections vary in width but usually contain a rounded end. They may be found in abetalipoproteinemia and certain liver disorders.
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