Hemoglobin and Red Cell Indices

Dr. Sumaira Iqbal

Learning Objectives

• By the end of lecture student should be able to:

• Explain hemoglobin synthesis

• Summarize iron metabolism

• Comment on various type of anemias and polycythemias

• Relate RBCs indices to diagnose type of anemia and its physiological basis

Haemoglobin(Hb)

• Hb is a conjugated protein of metaloporphyrin

• It is the red pigment inside the RBC.

• Heam- 4% Globin- 96%

• Molecular weight is 68000

• Adult Male—13 – 18 g/dl

• Adult Female—11.5 - 16.5 g/dl

• Testosterone stimulate Erythropoiesis, for that Hb level is higher than female

Functions of Haemoglobin

• Transport oxygen from lung to tissues •

• Transport CO2 to lungs

• Maintains acid base balance ( As a Buffer)

• Reserves Fe & Proteins

Synthesis of Hemoglobin

• 2 succinyl CoA + 2 glycine →Pyrrole

• 4 Pyrrole → Protoporphyrin IX

• Protoporphyrin IX + Fe2 →Heme

• Heme + Globin 4 polypeptide chains →αß(2 Alpha+ 2 Beta)

• 2αchain+ 2ß chain → Hemoglobin A

• 4 units of Haem attached to 1 unit of Globin

• 1 Haemoglobin molecules contains 4 Iron Atoms which reversibly binds 4 molecules of oxygen.

• It loosely bind via co-ordination bond

Hemoglobin Catabolism

• Macrophages, mainly the Kupffer cells in the liver phagocytose Hemoglobin

• HEMOGLOBIN = HEME + GLOBIN

• HEME releases Fe++ converts into PORPHYRIN

• PORPHYRIN turns into BILVERDIN + CO

• CO expelled via lungs and

• Bilverdin reduced to bilirubin and sent to blood & liver for excretion

• 1 gm of hemoglobin, when fully saturated, combines with 1.34 ml of oxygen.

• Hemoglobin concentration is therefore an index of the oxygen carrying capacity of the blood

IRON

• Iron is one of the most essential trace element

• Total body iron content is 3 to 5 g.

• 75% present in blood, the rest is in liver, bone marrow & muscles.

• Iron is present in almost all cells.

• The best sources of food iron include liver, meat, egg yolk, green leafy vegetables, dates, whole grains and cereals

Metabolism of iron

• Absorption:

– Iron is called as one way substance, because it is absorbed and excreted from small intestine.

• Iron is absorbed in three forms: (1) ferrous iron (2) ferric iron (3) heme iron.

• Iron is absorbed mainly in the ferrous form.

Transport of Iron

• Major sources of iron in the plasma is from degraded erythrocytes.

• Fe3+ combines with apoferritin to form ferritin, which the temporary storage form of iron.

Transport of iron

• From the mucosal cells, iron may enter the blood stream.

• Transport of iron in the plasma iron enters plasma in ferrous state and oxidized to ferric form by a copper containing protein, ceruloplasmin - ferroxidase activity.

• Ferric iron binds with a specific iron binding protein-transferrin (transport form)

Transport of iron

• Apotransferrin– glycoprotein, synthesized in liver Normal plasma level of transferrin is 250 mg/dl

• One molecule of transferrin can transport 2 ferric atoms and the half-life of transferrin is 7- 10 days.

• Serum iron and serum iron binding capacity:– Total iron binding capacity (TIBC) of transferrin is

250-450 µg/dl

Storage of iron

• Iron is stored in liver, spleen & bone marrow in the form of ferritin.

• In the mucosal cells, ferritin is the temporary storage form of iron.

• Ferritin contains about 23% iron.

• Ferritin in plasma level is elevated in iron over load.

• Ferritin level in blood is an index of body iron stores.

Storage of iron

• Ferritin is an acute phase reactant protein, elevated in inflammatory diseases

• Hemosiderin—another iron storage protein, which can hold about 35% of iron by weight

• Hemosiderin also accumulates when iron levels are increased.

Excretion of iron

• The normal Iron excretion is about 1mg/day. • The major excretory pathway is through intestine. • Iron is not excreted in urine, but in nephrotic syndrome loss of transferrin may lead to increased loss of iron in urine

Maturation of the RBC

• ↑ Synthesis of DNA (thymidine triphosphate)→ rapid proliferation of the erythroblastic cells –Requires Vitamin B12 and folic acid

• Lack of DNA – failure of mature RBCs—maturation failure• Macrocytes• Dietary B12—Parietal cells of gastric mucosa produce

intrinsic factor (IF). B12 binds with the IF – protection from digestion by GIT secretions Complex of Vit B12 +IF complex binds to the mucosal receptors in the ileum → transport across mucosa → red bone marrow or storage in the liver (very large quantities – 3-4 years reserve

• ANEMIA

CLASSIFICATION

SYMPTOMS

TREATMENT

• POLYCYTHEMIA

TYPES

TREATMENT

• RED CELL INDICES

Red Cell Indices

Blood tests that provide information about the hemoglobin content and size of red blood cells.

a. MEAN CORPUSCULAR VOLUME:

• MCV gives the average size of a red blood cell

• is calculated by dividing the hematocrit (Hct) by the red blood cell count.

• MCV = Hct x 10

RBC

• Normal range: 79-96 fL

b. MEAN CORPUSCULAR HEMOGLOBIN:

• (MCH) is the average amount of hemoglobin (Hb) per red blood cell and is calculated by dividing the hemoglobin by the red blood cell count.

• MCH = Hb x 10

RBC

• Normal range: 27-32 pg/cell.

c. MEAN CORPUSCULAR HEMOGLOBIN CONCENTRATION:

• MCHC is the average concentration of hemoglobin per red blood cell and is calculated by dividing the hemoglobin by the hematocrit.

• MCHC = Hb x 100

Hct

• Normal range: 32-36 %

MCD

–Mean diameter of 500 cells

Normal value = 7.2 + 0.5 µm

CI (Color Index)

CI = Hb% (Ratio of HB% & RBC%)

RBC %

Normal value = 0.85-1.0

Packed cell volume/Hematocrit

• PCV is the volume of RBC in relation to that of whole blood

• Hematocrit literally means blood separation.

• It expressed as the volume of red blood cells per liter of whole blood.

• It may be also expressed as %.

– Men 40 – 54%

– Women 37 – 47%

Anemia

Anemia means deficiency of hemoglobin in the blood, which can be caused by either too few red blood cells or too little hemoglobin in the cells.

OR

Anemia can be brought about by a

• Decreased rate of erythropoiesis.

• Excessive losses of erythrocytes.

• Deficiency in the hemoglobin content of erythrocytes.

ANEMIA

RBC Count

WHO Classification

Degree Hb(g/dL) Hematocrit %

Mild 10 37

Moderate 7-10.9 24-37

Severe 4-6.9 13-23

Very severe <4 <13

1. BLOOD LOSSa. ACUTE BLOOD LOSS:

• Fluid portion of plasma is replaced in 1-3 days.

• Low conc of RBCs.

• No further loss, RBCs conc returns to normal within 3-6 weeks.

b. CHRONIC BLOOD LOSS:

Patient losing blood frequently not enough iron absorbed from intestine RBCs produced are smaller with less hemoglobin(MICROCYTIC HYPOCHROMIC).

2.IMPAIRED PRODUCTION

a. IRON DEFICIENCY ANEMIA:

• Blood loss.

• Gastrointestinal bleeding due to H.pylori infection, drugs etc.

• A lack of iron in the diet.

• An inability to absorb iron.

• Pregnancy.

Iron deficiency anemia

b. Megaloblastic Anemia:

DEFICIENCY OF INTRINSIC FACTOR AND VITAMIN B12

slow production of erythroblasts in bone marrow

Red cells grow immature& too large (megaloblast).

CAUSES:

• Atrophy of stomach mucosa pernicious

anemia.

• Loss of the entire stomach after surgical total

gastrectomy megaloblastic anemia.

• Achlorhydria.

• Chronic pancreatitis.

• Alcoholism

• Drugs.

CLINICAL PRESENTATION:

• Fatigue

• Neuropathy

• Beefy tongue

• Malabsorption

c. ANEMIA OF CHRONIC DISEASES:

• Diseases such as

– Cancer

– HIV/AIDS,

– Rheumatoid arthritis,

– Crohn's disease and other chronic inflammatory diseases.

• Can interfere with the production of red blood cells, resulting in chronic anemia.

• Kidney failure also can cause of chronic anemia.

d. APLASTIC ANEMIA:

• Person exposed to high-dose radiation or chemotherapy for cancer treatment can damage stem cells of the bone marrow.

• Due to lack of functioning marrow

3.HEMOLYSIS ( SED DESTRUCTION)

a. Extrinsic to RBCs:

Autoimmune diseases such as systemic lupus erythematosus

Physical & chemical agents high doses of certain toxic chemicals, such as insecticides or benzene in gasoline.

may lead to aplastic anemia as well.

Erythroblastosis fetalis

• is an alloimmune condition of fetus.

• Occur when IgG molecules produced by mother pass through placenta.

• Mother must be Rh negative and the child must be Rh positive for the immunologic attack to occur.

• Antibodies attack the red blood cells in the fetal circulation.

• The red cells are broken down and the fetus can develop reticulocytosis and anemia.

b. Intrinsic to RBCs:

• Membrane defects hereditary spherocytosis.

• Hemoglobinopathies Thallasemia, sickle cell diseases.

• Enzyme deficiencies G6PD deficiency, Pyruvate kinase deficiency.

Sickle cell anemia

• Autosomal recessive disorder

• Valine is replaced by glutamic acid in beta chain—abnormal hemoglobin HbS

• Low Oxygen concentration Hb precipitates

• Damages cell membrane—cell disrupts—serious hemolysis

• Hemolysis leads to reduced oxygen further sickling occurs more hemolysis –sickle cell crisis

Hereditary Spherocytosis

• RBCs loses biconcave bag like shape

• Spherical

• Disrupts when pass through tight vascular beds upon slight compression

Morphological Classification:

MICROCYTIC HYPOCHROMIC

• Iron deficiency

• Thalassemia

• Anemia of chronic disease

MACROCYTIC HYPOCHROMIC

Megaloblastic

• Vitamin B12 deficiency

• Folate deficiency

Nonmegaloblastic

• Myelodysplasia

NORMOCYTIC NORMOCHROMIC

• Acute blood loss

• Dual deficiency

• Anemia of chronic disease

• Hemolytic anemia

• Aplastic anemia

• Marrow infiltration

Treatment

• Treat the underlying cause• Check iron profile, if deficient, iron replacement

should be done• Check Vitamin B12 and folate status should be

monitored and maintained• In chronic disease like renal failure,

erythropoietin should be given• Bone marrow biopsy to rule out bone marrow

failure• Constant monitoring of reticulocyte count

POLYCYTHEMIA• Polycythemia is characterized by too many

circulating RBCs and an elevated hematocrit.

• The RBC count may reach 11 million cells/mm3.

• The hematocrit may be as high as 70% to 80%.

PRIMARY POLYCYTHEMIA

• Is caused by a tumor like condition of bone marrow.

• In this erythropoiesis proceeds at an excessive,

uncontrolled rate beyond erythropoietin regulatory mechanism.

SECONDARY POLYCYTHEMIA:

• When tissues become hypoxic because of little oxygen in the breathed air, as at high altitudes(physiological polycythemia).

• Failure of oxygen delivery to the tissues, as in cardiac failure.

• Blood-forming organs automatically produce large quantities of extra red blood cells.

RELATIVE POLYCYTHEMIA

• An elevated hematocrit can occur when the body loses fluid but not erythrocytes, as in dehydration accompanying heavy sweating or profuse diarrhea.

• This is not true polycythemia because the number of circulating RBCs is not increased.

Treatment

• Goal of the treatment is to control the symptoms and reduce risk of complication.

Treatment:

1. Analgesics for symptomatic relief

2. Phlebotomy

3. Myelosupressive drugs

4. Radiation

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