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Introduction to Hematology and Basic Laboratory Practice

Introduction to Hematology

The Microscope

Significant Parts of the Microscope Care of the Microscope Corrective Actions in Light Microscopy Innovations in Microscopy

Standard Precautions

Personal Protective Equipment

Safety Features Other Than Personal Protective Equipment

Chemical and Environmental Hazards

Basic Concepts of Quality Assurance Plans in the Hematology Laboratory

Quality Control Monitoring in the Hematology Laboratory

Normal, or Reference, Intervals

Delta Checks

Reflex Testing

Preanalytic Variables

Postanalytic Variables

Critical Results

Objectives

After completing this chapter, the student will be able to:

1. Describe the significance of the field of hematology in relation to sickness and health.

2. List the basic parts of the compound microscope.

3. Discuss the function and magnification of each of the microscope objectives.

4. Identify appropriate corrective actions when encountering routine problems with the operation of a microscope.

5. Define standard precautions as related to biological hazards.

6. Describe safe work practices for personal protective equipment and disposal of biological hazards.

7. Describe the components of quality assurance in the hematology laboratory.

8. Define the terms preanalytic and postanalytic variables, delta checks, accuracy, precision, reproducibility, and reference intervals.

9. Formulate a plan of action based on the troubleshooting scenarios presented within the text.

4 Part I • Basic Hematology Principles

In its most fundamental form, hematology is the study of blood in health and in pathological conditions. Blood is the window to the body; it is a predictor of vitality, of long life. In ancient times, blood was worshipped. Men were bled to obtain a cure, and blood was studied for its mystical powers. It was an elevated bodily fluid. The discipline of hematology was an outgrowth of this fascination with blood. As we practice it in the clinical laboratory today, this discipline encompasses skill, art, and instinct. For those of us who are passionate about this subject, it is the art of hematology that so intrigues us. To view a peripheral smear and to have the knowledge not only to correctly identify the patient's hematological condition but also to predict how the bone marrow may have contributed to that condition is an awesome feeling. Hematology is about relationships: the relationship of the bone marrow to the systemic circulation, the relationship of the plasma environment to the red cell life span, and the relationship of the hemoglobin to the red cell. For most students, hematology is a difficult subject to master because it forces students to think in an unnatural way. Instructors are always asking, Why? Why does this cell appear in the peripheral smear? What relationship does it have to the bone marrow? How was it formed? Many students begin a hematology course with little foundation in blood cell morphology. They have no real grasp of medical terminology and few facts concerning blood diseases. They are not equipped to answer Why? As instructors, our goal is to guide the student toward an appreciation of his or her role as a clinical laboratorian in hematology. Certainly we can help the student to develop the morphological and analytic skills necessary for adept practice in the hematology laboratory. Yet, to be truly notable in this field, keen instincts concerning a set of results, a particular cell, or a patient history play a defining role.

Blood has always been a fascinating subject for authors, poets, scholars, and scientists. References to blood appear in hieroglyphics, in the Bible, in ancient pottery, and in literature. Hippocrates laid the foundation for hematology with his theory of the body's four humors—blood, phlegm, black bile, and yellow bile— and his concept that all blood ailments resulted from a disorder in the balance of these humors. Unfortunately, these principles remained unchallenged for 1400 years! Gradually, men of science such as Galen, Harvey, van Leeuwenhoek, Virchow, and Ehrlich were able to elevate hematology into a discipline of medicine with basic morphological observations that can be traced to a distinct pathophysiology. It is to these men that we owe a huge debt of gratitude. Although they had little in the way of advanced technology, their inventions and observations helped describe and quantify cells, cellular structure, and function. Much of what has been learned concerning the etiology of hematological disease has been discovered since the 1920s, and therefore hematology, as a distinct branch of medicine, is in its early stages.1

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