Erythrocytes and Anemia

• Anemia is a disorder of erythrocytes, specifically iron deficiency anemia (IDA)
• The lecturer is Ali M. Al-Talafha from the Hematology Department of Applied Biology

Erythrocyte Function and Anemia

• Red blood cells (RBCs) deliver oxygen to tissues
• Hemoglobin within RBCs binds oxygen in the lungs and releases it in tissues
• Anemia comes from the Greek word "anaimia" meaning "without blood"
• Decreased hemoglobin or RBCs results in hypoxia
• Anemia affects an estimated 1.62 billion people worldwide

Classification of Anemia - Etiology

• Anemia can be classified by etiology
• Etiologies include excessive blood loss, inadequate erythropoiesis, and excessive hemolysis

Classification of Anemia - RBC Morphology

• Anemia can be classified by RBC morphology based on Red Blood Cell Mean Volume (MCV)
• MCV can either be Low (Microcytic), Normal (Normocytic), or High (Macrocytic)
• Microcytic with MCV < 80 fL includes iron deficiency anemia and Anemia of chronic inflammation
• Macrocytic with MCV > 100 fL includes Vitamin B12 and Folate deficiencies
• Normocytic with MCV 80-100 fL may have normal or low reticulocytes

Definition of Anemia

• Anemia is a reduction in hemoglobin content of blood
• It can be caused by decreased RBCs, hemoglobin, and hematocrit
• Diagnosis is based on history, physical examination, symptoms, and laboratory results
• Contributing factors include diet, medications, and bleeding history

Symptoms of Anemia

• Symptoms include fatigue, dizziness, paleness, coldness, shortness of breath, and weakness

Mechanisms of Anemia

• The life span of an RBC is approximately 120 days
• A healthy individual removes about 1% of RBCs due to senescence daily
• Bone marrow produces RBCs to replace those lost
• Hematopoietic stem cells differentiate into erythroid precursors
• Bone marrow releases reticulocytes that mature into RBCs
• RBC production requires iron, vitamin B12, and folate
• Globin synthesis must also function normally

Mechanisms of Anemia - Continued

• Bone marrow increases RBC production with excessive bleeding or hemolysis
• Anemia may develop as a result of ineffective and insufficient erythropoiesis, blood loss, and hemolysis

Ineffective and Insufficient Erythropoiesis

• Ineffective erythropoiesis produces defective erythroid precursor cells
• Precursors die in the bone marrow before maturing
• Conditions like megaloblastic anemia, thalassemia, and sideroblastic anemia involve ineffective erythropoiesis
• Peripheral blood hemoglobin is low, stimulating erythropoietin
• Despite a high RBC production rate, the resulting number of circulating RBCs is decreased
• Insufficient erythropoiesis decreases the number of erythroid precursors
• Factors leading to decreased RBC production include iron deficiency, lack of erythropoietin and autoimmune reactions

Blood Loss and Hemolysis

• Anemia results from acute or chronic blood loss
• Increased hemolysis shortens RBC lifespan, increasing anemia risk
• Chronic blood loss induces iron deficiency
• With acute blood loss or excessive hemolysis, bone marrow takes days for increased RBC production
• With traumatic hemorrhage or conditions with a high hemolysis rate and shortened RBC survival, the response may not compensate

Laboratory Diagnosis of Anemia - CBC

• Anemia detection requires a complete blood count (CBC) using an automated hematology analyzer
• This determines RBC count, hemoglobin concentration, hematocrit, RBC indices, white blood cell count, and platelet count
• MCV is the most important measure among RBC indices
• Reticulocyte count assesses the bone marrow's response to anemia
• Adult reference interval for reticulocyte count is 0.5% to 2.5%
• Newborn values are higher (1.5 – 6.0%) but change within weeks

Complete Blood Count (CBC) and Indices

• Erythrocyte parameters include count, hemoglobin (Hb), and hematocrit (PCV)
• Male ranges differ from female ranges
• Indices include Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), Mean Corpuscular Hemoglobin Concentration (MCHC), and Red Cell Distribution Width (RDW)
• Hemoglobin levels vary between infants, children, menstruating/pregnant women, and men

Peripheral Blood Film Examination

• Evaluation of anemia includes examination of the peripheral blood film
• Check for RBC diameter, shape, color, and inclusions
• The blood film verifies the results produced by automated analyzers
• Shape abnormalities (sickle cells) and RBC inclusions can be detected

Bone Marrow Examination

• The cause of anemias can be determined from history, physical examination, and lab tests of peripheral blood
• If the cause cannot be determined or remains broad, perform bone marrow aspiration and biopsy
• Indicated when unexplained anemia is associated with other cytopenias, fever, or malignancy suspicion
• Bone marrow exams evaluate hematopoiesis and detect abnormal cell infiltration
• The underlying cause of anemia can be determined (e.g., iron stains)

Other Laboratory Tests

• Urinalysis (to detect hemoglobinuria or an increase in urobilinogen) with a microscopic examination (to detect hematuria or hemosiderin)
• Analysis of stool (to detect occult blood or intestinal parasites)
• Useful chemistry studies include serum lactate dehydrogenase (LDH) and unconjugated bilirubin (to detect excessive hemolysis)
• Iron studies (to determine serum iron, total iron-binding capacity, transferrin saturation, and serum ferritin) are valuable if an inappropriately low reticulocyte count and a microcytic anemia are present.
• Serum vitamin B12 and serum folate assays are helpful in investigating a macrocytic anemia

Iron Deficiency Anemia (IDA)

• Iron deficiency is the commonest cause of anemia worldwide
• In the US, iron deficiency is common among childbearing age women and in infancy
• In men and non-menstruating women, iron deficiency is often a result of blood loss

Iron Deficiency Anemia - continued

• Anemia occurs once body iron stores have been used up
• Iron is one of the commonest elements in the earth's crust
• The body has a limited ability to absorb iron so hemorrhage causes deficiencies

Body Iron Distribution (Iron Homeostasis)

• Hemoglobin contains about two-thirds of body iron
• Iron is incorporated from plasma transferrin into developing erythroblasts and reticulocytes in the bone marrow
• Transferrin obtains iron mainly from reticuloendothelial (RE) cells (macrophages)
• Only a small proportion of plasma iron comes from dietary iron absorbed through the duodenum and jejunum
• At the end of their life, red cells are broken down in the macrophages of the RE system and their iron is subsequently released into the plasma

Iron Containing Compounds

• Most of the body's iron, heme iron, is contained within the heme moiety of hemoglobin, with smaller amounts in myoglobin and other iron-containing non-heme proteins and cellular enzymes
• Storage iron is sequestered in a nontoxic form in ferritin and hemosiderin within the RE system and liver
• Iron in ferritin and hemosiderin is in the ferric form (Fe3+)
• A small but essential amount of iron circulates in the plasma bound to transferrin

Dietary Iron - Iron Requirements

• Iron in food comes in two forms: heme iron and non-heme iron
• Non-heme iron is found in plant foods and iron-fortified food products
• Meat, seafood, and poultry have both heme and non-heme iron
• Ferric (Fe3+) iron in food must be reduced to ferrous (Fe2+) iron before absorption
• The low-pH environment in the stomach solubilizes the iron
• The average Western diet contains 10-15 mg of iron from which only 5-10% is normally absorbed
• The proportion can be increased to 20-30% in iron deficiency or pregnancy
• 1mL of erythrocytes contains 1mg of Iron.
• Daily needs of iron is between 20-25 mg.
• 95% of requirements recycled after erythrocyte senescence.
• Iron loss occurs through skin, urinary, and fecal Excretions (0.5-1.0 mg), Menstruation (0.5 – 1.0 mg), and Pregnancy (1.0-2.0 mg/Neonate store 300 mg).

Iron Deficiency Anemia - Etiology

• Iron deficiency is caused by an inadequate iron supply for hematopoiesis and depletion of RE stores
• At an early stage, there are usually no clinical abnormalities
• Later, the patient may develop general symptoms and signs of anemia

Iron Deficiency Anemia - Stages

• Stage 1: Iron depletion stage is asymptomatic with normal CBC parameters
• Stage 2: Defective erythropoiesis has a depleted iron store with slow erythropoiesis
• Stage 3: Anemia

Iron Deficiency Anemia - Clinical Features

• Patients can be asymptomatic or suffer from anemia symptoms (fatigue, weakness, pallor, palpitations, dizziness, headaches, tinnitus, shortness of breath)
• May also experience GI symptoms (abdominal pain/melena, positive fecal occult blood test) or gynecological symptoms (heavy menses, cramping)
• Manifestations relate to the direct effects of iron deficiency
• Pallor is present in the conjunctiva, sublingual area, and hands

Iron Deficiency Anemia - Clinical Features continued

• Smooth tongue: Painless, smooth, shiny, and reddened tongue
• Koilonychia (spoon-shaped nails): Thin, fragile, and concave with raised edges
• Angular Cheilosis: Ulceration of the corners of the mouth

Iron Deficiency Anemia - Diagnosis

• Lab findings include reduced serum iron and ferritin, with increased TIBC (<10% TF saturation) and serum transferrin receptors
• Red cell indices fall progressively as anemia becomes severe

Iron Deficiency Anemia - Diagnosis continued

• A peripheral blood film shows hypochromic, microcytic cells with occasional target cells and pencil-shaped poikilocytosis
• The reticulocyte count is low in relation to the degree of anemia
• When iron deficiency is associated with severe folate or vitamin B12 deficiency, there is a 'dimorphic' film
• A dimorphic blood film is also seen in patients with iron deficiency anemia who have received recent iron
• Platelet count often is moderately raised, particularly when hemorrhage is continuing.

Iron Deficiency Anemia - Diagnosis continued

• Bone marrow examination is not essential except in complicated cases, for iron stores
• Perl's Prussian blue histopathology stain is used to detect iron presence
• In iron deficiency anemia, iron is completely absent from storage and siderotic iron granules from developing erythroblasts