hematology

HEMATOLOGY

WHAT IS HEMATOLOGY?

Hematology is the study of blood, blood-forming organs, and blood-related diseases as well as the diagnosis, treatment, and prevention of those diseases.

Diseases include those of the immunologic,

hemostatic, and vascular systems.

The history of hematology can be traced to the time of Ancient Egypt, where “bloodletting” instruments were often used. However, hematology only began to really flourish by the beginning of the 1600s.

Physicians who specialize in this field are called hematologists. Physicians who work in hematology laboratories and most commonly manage them are referred to as hematopathologists.

ROUTINE HEMATOLOGY PROCEDURES

1.) COMPLETE BLOOD COUNT (CBC)

Consists of the following tests: The WBC count; The RBC count; Hemoglobinometry; The measurement of hematocrit; The white blood cell differential; and The red blood cell indices.

IMPORTANCE OF THE CBC Is helpful in the diagnosis of many diseases. Is an indicator of the body’s ability to fight

disease. Used to monitor the effects of drug and

radiation therapy. May be employed as an indicator of the patient’s progress in certain diseased states such as infection or anemia.

2.) HEMOGLOBINOMETRY

Measurement of the concentration of hemoglobin in the blood.

One type of test used to diagnose and to follow the treatment of anemia.

Cyanmethemoglobin Method – blood is mixed with Drabkin’s solution, which eventually forms cyanmethemoglobin. Cyanmethemoglobin produces a color which is measured in a colorimeter, spectrophotometer, or automated instrument. The color relates to the concentration of hemoglobin in the blood.

Haden-Hausse or Sahli-Hellige Method – blood is mixed with dilute hydrochloric acid. This process hemolyzes the red cells and the hemoglobin is released, which is then converted to a brownish-colored solution of acid hematin. The acid hematin solution is then compared with a color standard.

Ferricyanide & Cyanide

1. Ferricyanide oxidizes the iron in hemoglobin so that Hemoglobin → Methemoglobin2. Methemoglobin + Cyanide →

Cyanmethemoglobin

3.) HEMATOCRIT

Measures the proportion of a person’s blood that is made up of RBCs. Is decreased in anemia and increased in

various forms of polycythemia. One of the simplest and most reproducible

of any laboratory test. Reading closely parallels the hemoglobin

values, so that fluctuations seen in the hemoglobin will also be reflected in the hematocrit.

Microhematocrit Method – whole blood is centrifuged for maximum red blood cell packing. The space occupied by the red blood cells is measured and expressed as a percentage of the whole blood volume.

4.) WHITE BLOOD CELL COUNT

Denotes the number of white blood cells in 1 liter (L) of whole blood.

Utilized to indicate infection. May also be employed to follow the progress of

certain diseases and therapies. Elevates in bacterial infections, appendicitis,

leukemia, and ulcers and drops below normal values in viral diseases, typhoid fever, infectious hepatitis, and rheumatoid arthritis.

A white count above 11.0 x 109/L is termed leukocytosis. A white count below normal is known as leukopenia.

Manual White Blood Cell Count – whole blood is mixed with a weak acid solution that lyses nonnucleated red blood cells. The specimen is then introduced into a counting chamber where the white blood cells are counted.

5.) RED BLOOD CELL COUNT

Number of red blood cells/liter (L) of whole blood. There are two basic methods: the manual method

and the procedure employing an electronic cell counter.

Increased in polycythemia, myeloproliferative disorders, and dehydration and decreased in anemia, acute leukemia, hemorrhage, and hemolysis.

The most common type of anemia, iron-deficiency anemia, occurs because the marrow

fails to produce sufficient red blood cells.

6.) DIFFERENTIAL CELL COUNT

Enumeration of the different white blood cell types circulating in the blood.

Called “differential” count because all enumerated cells are brought into a common mathematical context.

7.) RED BLOOD CELL INDICES

Defines the size and hemoglobin content of the red blood cell.

Consist of the mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC).

Commonly used as an aid in diagnosing and differentiating anemias.

8.) ERYTHROCYTE SEDIMENTATION RATE A nonspecific measurement of the rate

at which the erythrocytes settle from the plasma.

Affected by three factors: Protein composition of the plasma; Size and shape of the erythrocytes; and Erythrocyte concentration.

Westergren Method – whole blood is anticoagulated with trisodium citrate, placed in a Westergren pipet, and allowed to stand for exactly 1 hour in a vertical position. The number of millimeters the red blood cells fall during this times period constitutes the ESR.

Wintrobe and Landsberg Method – well-mixed, whole blood is placed in a Winstrobe tube and allowed to stand for 1 hour. The number of millimeters the red blood cells fall during this time constitutes the ESR.

9.) RETICULOCYTE COUNT

Determines if the bone marrow is responding adequately to the body’s need for red blood cells.

Determines the cause of as well as to classify different types of anemia.

A decreased reticulocyte count is found in aplastic anemia.

Increased reticulocyte counts are found in hemolytic anemias, individuals with iron deficiency anemia receiving iron therapy, thalassemia, and in acute and chronic blood loss.

Principle: Using a supravital stain, residual RNA within the reticulocytes is precipitated. An equal volume of stain is added to EDTA-anticoagulated blood and a smear is prepared. The smear is examined to determine the number of reticulocytes present.

10.) PLATELET COUNT

An increased platelet count, thrombocytosis, is found in polycythemia vera, idiopathic thrombocythemia, and chronic myelogenous leukemia.

A decreased platelet count, thrombocytopenia, occurs in aplastic anemia, acute leukemia, Gaucher’s disease, and sometimes following chemotherapy and radiation therapy.

There are two general methods: the usage of the phase microscope and the usage of an automated cell counter.

Principle: Whole blood is diluted with ammonium oxalate, which lyses the erythrocytes but preserves leukocytes and platelets. The diluted blood is then added to the hemacytometer chamber. Cells are allowed to settle for 10 minutes before leukocytes and platelets are counted.

11.) EOSINOPHIL COUNT

Principle: Whole blood is diluted with a staining solution. The phyloxine B present in the diluting fluid stains only the eosinophils red; all other leukocytes are preserved but not stained. The diluted specimen is charged onto a hemacytometer for counting. Using a low power objective, the eosinophils appear bright orange-red and are clearly distinguishable.

*There are two general methods: • The indirect method (white

blood cell count multiplied by the percentage of eosinophils in the differential), and

• The direct method.

12.) SICKLE CELL TESTS

Some anemias are the result of increased destruction of red blood cells, as in the case of sickle-cell anemia, a genetic disease most common in persons of African ancestry. The red blood cells of sickle-cell patients assume an unusual crescent shape, causing them to become trapped in some blood vessels, blocking the flow of other blood cells to tissues and depriving them of oxygen.

Sodium Metabisulfite Method and Solubility Test – in both methods certain chemicals are added to the blood sample. Under these conditions, hemoglobin S present in the red blood cell causes the formation of sickle-shaped red cells.

PROFESSIONS IN HEMATOLOGY

FEATURES

The hematologist must be skilled and knowledgeable in treating all types of afflictions.

This job is generally regarded to be highly demanding as compared to other types of professions in the medical field

Hematologists work with their patients every step of the way.

WORKPLACES

They may expect to spend some of their time in a lab analyzing blood samples or at a hospital or medical facility, performing procedures or surgeries.

OUTLOOK AND SALARY

The job opportunities or employment outlook for hematologists is very good.

Salary is contingent upon: Experience, Training, and Job performance.

The job is commonly regarded as more interesting and more varied than those of other physicians, which also add to its appeal in the medical world, making it one of the most popular choices.

REQUIREMENTS

An undergraduate course should be taken initially to be able to get an adequate foundation in the medical course proper.

Medical school is the next step and will take approximately four years to complete.

A four-year residency program is next. Official hematology training begins right

after the completion of a medical residency, which is an additional ten years.

TO SUM UP…

Hematology is a field of medicine primarily concerned with the study of blood and blood-forming tissues as well as the diseases related to them.

TO SUM UP…

Hematologists perform laboratory-based blood tests used in the detection of various disorders present in the blood, as well as abnormal cells, blood diseases, and other types of disorders detectable in the blood, such as hepatitis C.

TO SUM UP…

Another function of the hematologist is to ensure the safety of donated blood by designing and implementing a variety of tests to detect the presence of infectious diseases.

IN CONCLUSION

It can be said that hematology plays an important and valuable role in laboratory medicine and in the maintenance of health.

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