Understanding Anemia

Anemia Definition

• Anemia is best defined as a decreased hemoglobin, hematocrit, and red cell count, compared with typical results for a similar demographic

Hemoglobin Concentrations

• Two patients have hemoglobin levels between 5.0 to 6.0 g/dL
• One patient experiences pallor, fatigue, and headaches
• The other is experiencing life-threatening shock
• The major difference between the two patients is how quickly the anemia developed

Anemia Development

• The body compensates when anemia develops slowly, resulting in few symptoms
• Rapidly developing anemia, such as from massive blood loss, shows evident symptoms

Red Cell Histograms

• When a red cell histogram is wider than normal, anisocytosis is present
• The coefficient of variation of the red cell histogram is the RDW (red blood cell distribution width)
• When the histogram is broader than usual, the RDW increases

Reticulocyte Response

• Reticulocyte response in moderate anemia can be misinterpreted if the count is not corrected for anemia
• A truer picture of bone marrow response adequacy is obtained when considering the red count and calculating either the absolute reticulocyte count or the reticulocyte production index

Red Blood Cell Findings

• Sickle cells are a specific red blood cell finding, almost diagnostic for sickle cell disease
• Many abnormally shaped red blood cells are nonspecific for any one cause of anemia

Bone Marrow Aspiration

• A bone marrow aspiration is warranted when a patient is anemic with no obvious reason after initial testing
• This allows evaluation of the morphology of erythroid and all other blood-forming cells in the marrow, which gives information on the cause of anemia

RBC Lifespan

• The average life span of a normal red blood cell in circulation is 120 days

Red Cell Replacement

• Approximately 1% of red cells are destroyed and replaced daily, given their 120-day lifespan

Morphologic Anemia Classification

• Normocytic anemia is an example of a morphologic classification of anemia
• Morphologic classification uses red cell morphology to separate anemias into groups, linking them to potential causes

Macrocytic Anemia

• Folate deficiency is typically a macrocytic anemia
• Iron deficiency anemia (stage 3) and thalassemia are microcytic
• Aplastic anemia is normocytic

Morphological Anemia Classification

• The RDW (red cell distribution width) is used with the MCV (mean cell volume) to classify anemias morphologically
• The RDW indicates whether the red cell population is homogenous or heterogeneous in size

Physiological Adaptations

• When there is a slow drop in the number of red cells, the oxygen dissociation curve shifts to the right (2,3-BPG increases)
• Other physiological adaptations include increased cardiac output and respiratory rate

Red Cell Indices

RBC: 1.89 × 1012/L, Hemoglobin: 7.5 g/dL, Hematocrit: 21.0%, RDW: 18.5 indicates:

• Macrocytic red cells with anisocytosis
• MCV = 111 fL, MCH = 40 pg, and MCHC = 36, indicating macrocytic and normochromic cells
• The elevated RDW of 18.5 indicates an increased variation in size

Vitamin B12 Deficiency

• A disorder consistent with macrocytic red cells with anisocytosis is Vitamin B12 deficiency
• This leads to macrocytic anemia with significant variation in size (increased RDW)

Anemia Types & RDW

• Aplastic anemia is normocytic normochromic with a normal RDW
• Anemia of chronic inflammation can be normocytic or slightly microcytic but normochromic, with a normal to mildly elevated RDW
• Thalassemia is microcytic normochromic or hypochromic with a normal RDW

Ineffective Erythropoiesis

• Ineffective erythropoiesis has increased RBC production in the bone marrow
• Production is defective, and many red cells are destroyed before leaving the marrow
• Release of RBCs to peripheral blood is decreased, lymphopenia is not characteristic of these anemias

Erythropoiesis

• Both effective and ineffective erythropoiesis have an increased rate of red cell production in the bone marrow
• Release to circulation is successful in effective erythropoiesis but not in ineffective erythropoiesis, where significant intramedullary loss occurs

RPI Values

• The RPI (reticulocyte production index) is greater than 3 in effective erythropoiesis
• The RPI is usually less than 2 in ineffective erythropoiesis

Red Cell Survival

• Red cell survival in circulation is significantly decreased in effective erythropoiesis
• It is essentially normal or insignificantly shortened in ineffective erythropoiesis

Microcytic Anemia

• Iron deficiency is a microcytic anemia
• Vitamin B12 deficiency is macrocytic
• Sickle cell anemia and hereditary spherocytosis are both normocytic

Liver Disease Anemia

• The anemia found in liver disease is macrocytic nonmegaloblastic
• Large red cells result from membrane changes due to disruption of the cholesterol-to-phospholipids ratio in the membrane

Spherocyte Description

• A spherocyte is a round, dense red cell lacking a central pallor
• The MCV of a spherocyte is usually normal, microspherocytes have a low MCV

RPI Increase

• An appropriately increased RPI greater than 3 is associated with hemolytic anemia
• Only hemolytic anemias have an appropriately increased RPI, where anemia results from shortened survival in circulation
• Insufficient erythropoiesis occurs in iron deficiency anemia
• Erythropoiesis is ineffective in macrocytic megaloblastic and sideroblastic anemias

Dacryocyte Description

• A dacryocyte is a red blood cell with a single pointed extension, resembling a pear
• An echinocyte has blunt or pointed, short projections evenly spaced over the cell surface
• An acanthocyte is a small, dense red blood cell with few irregularly spaced projections
• A keratocyte is a red blood cell fragment shaped like a helmet