Laboratory Medicine and Hematopoiesis

Laboratory Quality Management

All the policies and procedures used to ensure that laboratory

results are reliable

Guidelines for Laboratory Quality Management are outlined by what organization?

American Society for Veterinary Clinical Pathology

Three types of laboratory error:

1.) pre-analytical

2.) analytical

3.) post-analytical

pre-analytical laboratory errors

occur prior to actual sample testing

Examples of pre-analytical laboratory errors

-not using correct patient and test

-not doing proper sample collection and handling

-not labeling and storage properly

-sample transport

Pre-analytical laboratory errors account for ___-___% of total errors!

52-77%

analytical laboratory errors

occurs during sample analysis by a pathologist

Examples of analytical laboratory errors

-equipment malfunction

-reagent expiration and degeneration

-pipetting errors

-quality control and assurance

post-analytical laboratory errors

errors that occur after results are generated

Examples of post-analytical laboratory errors

-transcription errors (writing wrong number/putting decimal in wrong place, etc)

-failure to report test results

-improper delivery of test results

-misinterpretation of results

Hematopoiesis

formation of blood cells; process through which all circulating blood cells are constantly regenerated

hematopoietic stem cells (HSC)

The cell type from which all lineages of blood cells arise

Where does hematopoiesis take place in adults?

red bone marrow (flat bones and ends of long bones)

Three things that are required for normal hematopoiesis:

1.) hematopoietic stem cells (HSC)

2.) growth factors

3.) bone marrow microenvironment

Hematopoietic tissue consists of three things:

1.) hematopoietic cells

2.) stromal tissue (fat, fibrous tissue)

3.) vascular sinuses lined by endothelium

hematopoietic stem cells (HSC) have the ability to _________ themselves through division

replenish

hematopoietic stem cells (HSC) differentiate into two main groups:

1.) myeloid progenitors

2.) lymphoid progenitors

Myeloid progenitors give rise to four cell types:

1.) RBCs

2.) granulocytes

3.) monocytes

4.) platelets

Lymphoid progenitors give rise to three cell types:

1.) T cells

2.) B cells

3.) natural killer cells

Erythropoiesis

Production of RBCs from

hematopoietic progenitor cells committed to the erythroid lineage

Two things required for erythropoiesis:

1.) iron

2.) erythropoietin (EPO)

iron for erythropoiesis is provided by...

macrophages

erythropoietin (EPO)

hormone secreted by the kidney to stimulate the production of red blood cells by bone marrow

The most immature stage of red blood cell development is called the...

rubriblast

Progression of Erythropoiesis starting with the rubriblast

rubriblast --> Prorubricyte --> Rubricyte --> Metrubricyte --> Polychromatophil --> mature RBC

Process of erythropoiesis (4):

-cell size and nuclear size decrease

-chromatin condensation increases

-nuclei are extruded

-cytoplasm becomes less basophilic

Why does the cytoplasm become less basophilic during erythropoiesis?

due to hemoglobin production, which will make the cell appear pink, as opposed to purple color (basophilic)

How long does it take for a rubriblast to differentiate into a mature RBC?

approximately 7 days

What stage of erythropoiesis will have the nucleus completely extruded?

Polychromatophil

Granulopoiesis

Production of neutrophils, eosinophils, and basophils from common myeloid progenitors and myeloid precursors

Myeloblast

immature bone marrow that gives rise to granulocytes

Progression of Granulopoiesis starting with the myeloblast

myeloblast --> promyelocyte --> myelocyte --> metamyelocyte --> band --> mature

Process of Granulopoiesis (3)

-size decreases,

-chromatin becomes more

condensed

-nucleus becomes segmented

Thrombopoiesis

formation of platelets from megakaryoblast

Progression of thrombopoiesis starting with Megakaryoblast

Megakaryoblast --> promegakaryocyte --> megakaryocyte

During thrombopoiesis, the _________ does not divide

nucleus

Megakaryocytes

large cells that develop into platelets; produce

cytoplasmic extensions that protrude into the lumen of the sinuses and form platelets

What hormone regulates thrombopoiesis?

thrombopoietin (TPO)

Complete Blood Count (CBC)

Determination of numbers of blood cells, hemoglobin concentration, hematocrit, and red cell values-MCH, MCV, MCHC

Five components of a CBC

1.) Erythrogram

2.) Leukogram

3.) Thrombogram

4.) Microscopic blood smear review

5.) Plasma protein

Erythrogram

The red cell portion of a CBC; includes RBC count, hematocrit (HCT), and hemoglobin (Hgb)

hematocrit (HCT)

percentage of red blood cells in the blood; aka PCV

Five indications for a CBC

1.) Healthy animal screening test

2.) Sick animal baseline laboratory data

3.) Determine the need for additional testing

4.) Monitor disease progression

5.) Evaluate response to therapy

Collection of blood samples for CBC

clean venipuncture with minimal excitation; site used for collection depends on species

Lavender top tube

contains EDTA which is an anticoagulant for CBC in mammals

EDTA

calcium chelating (binding) agent that is used as an anticoagulant for laboratory blood specimens

Red top tube

Contains no additive or anticoagulant; used for biochemical profiles

Green top tube

Used for CBCs in non-

mammalian species

Blue top tube

contains sodium citrate; used for coagulation tests

Whole blood

blood in EDTA; blood from which none of the elements have been removed.

Centrifuged samples of blood separate into three layers:

1.) plasma

2.) buffy coat

3.) RBCs

plasma

fluid portion of blood collected in a lavender top tube; water, proteins, lipids, and clotting factors

plasma vs serum

Plasma has clotting factors serum doesn't

buffy coat

platelets and WBCs

What color tube is used during a CBC?

lavender top tube

True or false: you must gently mix the blood prior to performing a CBC

true!

Why must you gently mix the blood prior to performing a CBC?

to allow EDTA to be evenly distributed to prevent clotting

Three functions of RBCs

1.) Carry O2 to cells

2) remove CO2 from tissues

3.) circulate back to the lungs to get more O2

Why are RBCs red?

due to protein hemoglobin (Hgb)

hemoglobin

molecule that carries oxygen; requires iron!

Six factors evaluated on a CBC:

1.) hematocrit

2.) RBC number

3.) hemoglobin

4.) size

5.) color

6.) variation in RBC ssize

hematocrit

calculated value; percentage of all the blood that is due to RBC

*aka PCV

size of RBC is measured in...

MCV

MCV

mean corpuscular volume; average red blood cell size

Three size categories for red blood cells:

1.) normocytic (normal)

2.) macrocytic (large)

3.) microcytic (small)

color of a RBC is based on...

how much hemoglobin is present in a cell

Two was color of RBCs is evaluated:

1.) MCHC

2.) CHCM

MCHC

mean corpuscular hemoglobin concentration; average concentration of hemoglobin in the volume of blood

CHCM

Corpuscular hemoglobin concentration mean; average concentration of hemoglobin in a single red blood cell

Two categories for color of red blood cells:

1.) normochromatic

2.) hypochromatic

Variation in RBC size is measured using...

red cell distribution width (RDW)

red cell distribution width (RDW)

Determines the range of sizes of RBCs

Numbers from a CBC are compared to what value?

reference interval (RI)

Blood smears are prepared using what stains?

Wright's stain or quick stain (Diff-quik)

Wright's stain

used for identifying heinz bodies and reticulocytes

quick stain (Diff-quik)

used for routine evaluation of blood smears