Chapter 1: An Overview of Clinical Laboratory HematologyHematology 1

Blood- transports oxygen from lungs to tissue clears tissues of carbon dioxide transports glucose, proteins, and fats Moves wastes to the liver and kidneys. Plasma The liquid portion of the blood among many other components coagulation enzymes that protect vessels from trauma and maintain the circulation Transports and nourishes blood cells.

Three families of blood cells1. red blood cells (RBCs) or erythrocytes2. white blood cells (WBCs) leukocytes3. platelets or thrombocytes

Hematology- the study of blood cellsWrights Romanowsky- type stain (polychromatic, a mixture of acidic and basic dyes) remains the heart of blood cell identificationRed Blood Cells Red Blood Cells (RBC) a nucleate biconcave cells filled with a reddish protein, hemoglobin (Hb, HGB) which trans- ports oxygen and carbon dioxide pink to red ; 6 to 8 m Anemia loss of oxygen-carrying capacity; reduced RBC count Polycythemia increased RBC count reflecting increased body RBC mass; leads to hyperviscosity

To count RBCs, laboratory scientists carefully pipetted a tiny aliquot of whole blood and mixed it with 0.85% (normal) saline. A 1 : 200 dilution was typical for RBC counts, and a glass pipette designed to provide this dilution

Thoma pipette used routinely until the advent of automation The diluted blood was transferred to a counting chamber or Report the RBC count in cells per microliter (mcL), milliliter (mL, also called cubic centimeter, or cc), or liter (L).

Coulter Counters first electronic counter by Joseph and Wallace Coulter of Chicago, Illinois, was used so widely that today automated cell counters Hemoglobin measurement relies on a weak solution of potassium cyanide and potassium ferricyanide, called Drabkin reagent. Hemoglobin is converted to stable cyanmethemoglobin(hemiglobincyanide), and the solution is placed in a photometer at 540 nm wavelength. Some automated hematology profiling instruments use a formulation of the ionic surfactant (detergent) sodium dodecyl sulfate to reduce environmental cyanide. Hematocrit ratio of the volume of RBCs to the volume of whole blood determined by transferring blood to a graduated plastic tube, centrifuging, measuring the column of RBCs, and dividing by the total length of RBCs plus plasma The normal ratio approaches 50% Also called packed cell volume (PCV), the packed cells referring to RBCs.

Buffy Coat light-colored layer between the RBCs and plasma Contains WBCs and platelets. Three Numerical Results1. RBC count2. Hemoglobin3. Hematocrit

To compute the RBC indices 1. mean cell volume (MCV)2. mean cell hemoglobin (MCH)3. mean cell hemoglobin concentration

Mean Cell Volume (MCV) measure of volume reflects RBC diameter on a Wright-stained blood film Mean Cell Hemoglobin Concentration (MCHC) reflects RBC staining intensity or degree of pallor Mean Cell Hemoglobin (MCH) expresses the mass of hemoglobin and closely reflects the MCHC RBC distribution width (RDW) expresses the degree of variation in RBC volume Extreme RBC volume variability is visible on the Wright-stained blood film as variation in diameter and is called anisocytosis. based on the standard deviation of RBC volume Reported by automated cell counters but cannot be provided using manual RBC measurements.RBC count, hemoglobin, hematocrit, indices, and RBC morphology are used to detect, diagnose, assess the severity of, and monitor the treatment of anemia, polycythemia, and numerous systemic conditions that affect RBCs Reticulocytes Polychromatophilic erythrocytes- in the Wright-stained film, 1% to 2% of RBCs exceed the 6- to 8-m ; slightly blue-gray newly released from the RBC production site, the bone marrow closely observed because they indicate bone marrow regeneration during blood loss and certain anemias Methylene blue dyes- called nucleic acid stains or vital stain used to differentiate and count these young RBCs Vital stains -dyes absorbed by live cells. Young RBCs contain ribonucleic acid (RNA) and are called reticulocytes when the RNA is highlighted using vital stains.White Blood Cells White Blood Cells or Leukocytes (WBC) are not really blood cells they are a loosely related grouping of cell families dedicated to protecting their host from infection and injury WBCs hitch a ride in the blood from their source, usually bone marrow or lymphoid tissue, to their tissue destination. They are so named because they are nearly colorless in an unstained cell suspension WBCs may be counted visually using a microscope, hema- cytometer, and a Thoma pipette The technique is the same as RBC counting, but the typical dilution is 1: 20, and the diluent is composed of dilute acetic acid in normal saline.

Chronic leukemia an extreme increase in the WBC count imparts a milky appearance to the blood **Acid causes RBCs to lyse or rupture Leukopenia decreased WBC count (fewer than 4500/mcL) Leukocytosis increased WBC count (more than 11,500/ mcL)

Types of White Blood Cells1. Polymorphonuclear neutrophils (PMNs, or segmented neutrophils or Segs phagocytic cells whose sole purpose is to engulf and destroy bacteria that have been earlier labeled as harmful by the immune system.

Neutrophilia increase in segs; signals bacterial infection. Neutropenia decrease in segs; caused by long-term drug administration or a viral infection.

2. Band neutrophils (bands) part of the seg family less differentiated or less mature than segs increase also signals bacterial infection and is customarily called a left shift The cytoplasm of segmented neutrophils and bands contains submicroscopic, pink-staining granules filled with bactericidal secretions.

3. Eosinophils (Eos) bright orange, regular cytoplasmic granules filled with antihistamine.

Eosinophilia elevated eosinophil count is called and signals a response to allergy or parasitic infection.

4. Basophils (basos) dark purple, irregular cytoplasmic granules that obscure the nucleus

Basophilia elevated basophil count signals a hematologic disease, such as leukemia.** Segs, bands, eosinophils, and basophils- collectively called granulocytes because of their prominent cytoplasmic granules Leukemia is uncontrolled proliferation of WBCs. may be chronic, for example chronic myelogenous (granulocytic) leukemia, or acute, such as acute myeloblastic leukemia

5. Lymphocytes (lymphs) Complex system of cells that provide for host immunity recognize foreign antigens and mount antibody (humoral) and cell-mediated antagonistic responses

Lymphocytosis Increase in the lymphocyte count; associated with viral infections. Lymphopenia or lymphocytopenia abnormally low lymphocyte count is and is associated with long-term drug therapy or immunodefi- ciency Chronic lymphocytic leukemia prevalent in people older than 70 years Acute lymphoblastic leukemia most common form of childhood leukemia

6. Monocytes (monos) immature macrophage passing through the blood from its point of origin, usually the bone marrow, to a targeted tissue location

Macrophages Most abundant cell in the body, more abundant than RBCs or skin cells, although they are a minor component of the blood film differential count Some are motile and some immobilized. Their task is to identify and phagocytose (engulf) foreign particles and assist the lymphocytes in mounting an immune response through the assembly and presentation of immunogenic epitopes Monocytosis An increase in the number of monocytes may signal a hematologic disease, such as leukemiaPlatelets Platelets or thrombocytes Are true blood cells that maintain blood vessel integrity by instigating vessel wall repairs Rapidly adhere to the surfaces of damaged blood vessels, form aggregates with neighboring platelets to plug the vessels, and secrete proteins and small molecules that trigger thrombosis, or clot formation. Platelets are the cells that control hemostasis, Hemostasis Series of cellular and plasma-based mechanisms that seals wounds, repairs vessel walls, and maintains vascular patency. Thrombocytosis Elevated platelet counts; signal inflammation or trauma but carry small intrinsic significance. Essential thrombocythemia rare malignant condition characterized by extremely high platelet counts and uncontrolled platelet production. Thrombocytopenia low platelet count a common consequence of drug treatment and may be life-threatening accounts for the majority of hemorrhage-related emergency department visits.

Complete Blood Count Complete Blood Count The scientist is responsible for the integrity of the specimen and ensures that it is free of clots, hemolysis, and inappropriate anticoagulant- to-specimen ratios known as short draws. When one of the results from the profiling instru- ment is abnormal, the instrument provides an indication of this, sometimes called a flag. In this case, the scientist performs a reflex blood film examination Blood Film Examination Blood Film Examination wedge-prep blood film on a glass microscope slide, allows it to dry, and fixes and stains it using Wright or Wright-Giemsa stain Endothelial cells Important in maintaining normal blood flow, in snaring platelets during times of injury, and in enabling WBCs to escape from the vessel to the surrounding tissue when called upon. Plasma coagulation is one component of hemostasis; another is platelets Coagulation system complex sequence of plasma proteins, some enzymes, and some enzyme cofactors to produce clot formation after blood vessel injury. Erythroid series precursors to RBCs Myeloid series cells mature to form bands and segmented neu- trophils, eosinophils, and basophils Megakaryocytes produce platelets Osmotic fragility test Uses graduated concentrations of saline solutions to detect spherocytes, RBCs with proportionally reduced surface membrane area, in hereditary spherocytic or warm autoim- mune hemolytic anemia Glucose-6-phosphate dehydrogenase assay tests For an inherited RBC enzyme deficiency causing severe episodic hemolytic anemia Hb electrophoresis used to detect and diagnose sickle cell anemia and other inherited qualitative hemoglobin abnormalities and thalassemias