Hematology Test 1 Chapter 1
What steps are included in the performance of a blood film examination?
- Prep a "wedge prep" blood film on a glass slide - Allow drying - Fix/stain it with Wrights or Wright-Giemsa stain - Microscopist visually performs an estimate of WBC count and platelet count. - Next the microscopist systematically reviews, identifies, and tabulaties 100 or more WBCs to to determine their percent distribution.
What are four major functions of blood?
- Transports oxygen from lungs to tissues. - clears tissues of carbon dioxide. - Transports glucose, proteins, and lipids. - Moves waste to liver and kidneys.
What are two types of bone marrow samples collected for analysis in the hematology laboratory?
Aspirates and biopsy specimens.
What are four examples of advanced hematologic procedures most often only performed in larger hospitals and specialty laboratories?
Bone marrow examinations, flow cytometry, cytogenetic analysis, and molecular diagnosis assays.
What does erythrocyte sedimentation rate measure?
detects inflammation and roughly estimates its intensity.
What is a hemacytometer?
device used for hand counting of cells
What are the three basic cellular elements in blood?
erythrocytes (red blood cells), leukocytes (white blood cells), and the thrombocytes (platelets).
Hematocrit is also called:
packed cell volume (PCV)
What does the glucose-6 phosphate dehydrogenase assay detect?
phenotypically detects an inherited RBC enzyme deficiency causing episodic hemolytic anemia.
What term is used to describe the liquid (non-cellular) portion of blood in the body?
plasma.
Thrombocytes
platelets
Which cells are granulocytes?
neutrophils, eosinophils, basophils.
What are bone marrow assays stains used for?
they are used to analyze nucleated cells that are the immature precursors to blood cells.
What are cytochemical stains used for?
they are used to differentiate abnormal myeloid, erythroid , and lymphoid cells.
What is the function of the stain used to differentiate and count reticulocytes?
they are used to indicate the ability of the bone marrow to increase RBC production in anemia caused by blood loss or excessive RBC destruction.
The morphology of blood cells is important to evaluate:
when a profiling instrument result is abnormal.
Leukocytes
white blood cells
How is the performance of a manual platelet count different from the performance of a manual WBC count?
Counting is usually confined to the center square millimeter of the hemacytometer. Owing to their miniscule volume, platelets are hard to distinguish
What are two key morphologic features of basophils on Wright-stained blood smears?
Dark purple, irregular cytoplasmic granules that obscure the nucleus.
What abnormal condition is represented by the term neutropenia?
Decrease in seg count.
What is the name of the key reagent used to measure hemoglobin?
Drabkin reagent.
Where are endothelial cells located? What are some of their important blood-related functions?
Endothelial cells line the blood vessel. They maintain normal blood flow, snare platelets during times of injury, and enable WBCs to escape from the vessel to surrounding tissue when needed
What are the names of the blood cells?
Erythrocytes- red blood cells (RBCs) Leukocytes - white blood cells (WBCs) Thrombocytes- platelets (PLTs)
What generic scientific adjective is used to describe bone marrow cells that are precursors to RBCs?
Erythroid
What are some examples of assays that are less frequently performed in coagulation laboratories?
Fibrinogen assay and D-dimer assay
Why might thrombocytopenia be life threatening?
It can be life threatening because thrombocytopenia is usually accompanied by easy bruising and uncontrolled hemorrhage
What is the composition of Drabkin reagent?
It is composed of a weak solution of potassium cyanide (KCN) and potassium ferricyanide (K3{Fe(CN6)}.
Describe how the hemacytometer is used in hematology.
It may be used for WBC differentials & counts, platelet counts, & erythrocyte (RBC) counts in hematology.
What abnormal condition is represented by the term leukocytosis?
Leukocytosis is an increased WBC count that is more than 11,500/mcL
What abnormal condition is represented by the term leukopenia?
Leukopenia is a decreased WBC count that is fewer than 4,500/mcL
What characteristic of the RBC population is described by the MCHC?
Measures the hemoglobin concentration per 100 mls packed RBC reflects RBC staining intensity or pallor Normal MCHC = Normochromic (normal hemoglobin concentration) Decreased MCHC = Hypochromic (decreased hemoglobin concentration)
Who is ultimately responsible for determining the specimen integrity before analysis?
Medical laboratory professional
What bone marrow cell type produces platelets?
Megakaryocytes
What does term flagged indicate on a CBC instrument?
One of the results from the profiling instrument is abnormal and the software shows a flag to bring attention to the result. If a flag is present, the scientist would perform a reflex blood film exam.
What is an alternate term for hematocrit?
Packed Cell Volume (PCV)
Why might essential thrombocythemia be life threatening?
People with essential thrombocythemia can have serious thromboembolic (seizures, transient ischemic attacks, cerebral or myocardial infarction) and hemorrhagic complications (bleeding from oral and nasal mucous membranes or gastrointestinal mucosa).
What are the two most fundamental components of hemostasis?
Plasma coagulation and platelets
How is the performance of a manual platelet count similar to the performance of a manual WBC count?
Platelets are counted using the same technique used in counting WBCs on a hemacytometer
What is the most fundamental physiologic function of platelets?
Platelets rapidly adhere to the surfaces of damaged blood vessels, for aggregates w/ neighboring platelets to plug the vessels, & secrete proteins & small molecules that trigger thrombosis, or clot formation
What is the meaning of the term polycythemia?
Polycythemia means an increased RBC count reflecting increased circulating RBC mass, a condition that leads to hyperviscosity
What term is often used to represent PMNs?
Polymorphonuclear neutrophils. Referred to as segmented neutrophils or segs.
What are the function and the key components of the coagulation system?
The function is to produce a clot formation after a blood vessel injury. The key components are a complex sequence of plasma proteins, some enzymes, & some enzyme co-factors which produce the clots, another 6-8 enzymes which regulate the coagulation mechanism, & 3rd set of enzymes & co-factors which digest the clots to allow the blood to flow again
What happens to a laboratory specimen when it is accessioned?
The laboratory scientist accurately registers the specimen in the work list. Accession can be automated using bar coding or RFID tags.
What phenomenon does the term buffy coat describe?
The light colored layer between RBC and plasma in Hemocrit PCV. Contains WBC's and platelets
What characteristic of the RBC populations is described by the RDW?
The red cell distribution width (RDW) reflects the degree of variation in size of the RBCs Compare the RDW and MCV to measure your red blood cell volume. A high MCV (larger RBCs) with a high RDW (showing size variation among RBCs, a high percentage of larger cells) occurs in some macrocytic anemias. A low MCV (smaller RBCs) with a high RDW (showing size variation among RBCs, a high percentage of smaller cells) occurs in microcytic anemias. So MCV tells you if they are large or small, and the RDW just lets you know there is a size variation among the RBC population within the patient. So, RDW can be increase with both small and large cell populations.
What are the key morphologic features of thrombocytes on Wright-stained blood smears?
They are only 2-4μm in diameter, round or oval, anucleate, & slightly granular
What are two key morphologic features of eosinophils on Wright-stained blood smears?
They are round and are bright orange-red cytoplasmic granules.
What is the function of fibrinolysis?
To break down the fibrin clot and restore patency (open, flowing) to the blood vessel
Briefly describe the procedure to measure hematocrits on anticoagulated whole blood specimens.
Transfer blood to a graduated plastic tube, centrifuge and measure the column of RBCs & dividing by the total length of RBCs + plasma
Why are white blood cells (WBCs) referred to as white?
WBCs are nearly colorless in an unstained suspension
What is the average volume of blood in humans?
5 L (5,000mL) of blood.
What are the four systems involved in hemostasis?
Coagulation, Platelets, Vascular, and Fibrinolytic.
What abnormal underlying condition or conditions may cause lymphocytosis?
an increase in lymphocytes count that is associated with viral infections
What is the appearance of immature RBCs (reticulocytes)on Wright-stained blood films?
0.5% to 2.5% of RBCs exceed the 7 - to 8 -μm diameter and stain slightly blue-gray.
What saline concentration provides the ideal osmolality for the study of RBCs?
0.85% (normal) saline matches the osmolarity of normal blood
What underlying abnormal conditions may induce eosinophilia?
A response to allergy or parasitic infection
Briefly describe the hand procedure to measure hemoglobin in anticoagulated whole blood specimens using Drabkin reagent?
A. An aliquot of whole blood is mixed with a measured amount of Drabkin reagent; B. This converts hemoglobin to stable cyanmethemoglobin (hemiglobincyanide). C. The absorbance or color intensity of the solution is measured in a spectrophotometer at 540 nm wavelength. D. The color intensity is compared with that of a known standard and is mathematically converted to hemoglobin concentration.
What abnormal condition is represented by the term eosinophilia?
An elevated eosinophil count
What is the meaning of the term anemia?
Anemia means loss of oxygen-carrying capacity and is often reflected in a reduced RBC count.
What underlying abnormal conditions may induce neutrophilia?
Bacterial infection
What term is often used to represent band neutrophils?
Bands
What is the relationship of band neutrophils to PMNs?
Bands are a part of the seg family. They are less differentiated or less mature than segs ( PMNs)
Under what pathologic circumstances has the blood itself been described as milky?
Chronic leukemia causes the blood to have a milk appearance due to extreme increases in WBCs
What are some specimen collection errors that will produce false complete blood count (CBC) results?
Clots due to improper mixing, hemolysis due to mechanical error, short draws which lead to improper anti-coagulant to specimen ratios
What are five minor blood specimen defects that may render it useless for coagulation laboratory assays?
Clots, hemolysis, lipemia, plasma bilirubin, and short draws
What abnormal condition is represented by the term neutrophilia?
Increase in seg count.
What aspects of RBCs are described when their morphology is described?
Morphology is the scientific term for the cell's appearance & includes cell color, size, shape, cytoplasmic inclusions, & nuclear condensation.
What generic scientific adjective is used to describe bone marrow cells that are precursors to monocytes, PMNs, and other granulocytes?
Myeloid
What is meant by the term polychromatophilic as used to describe erythrocytes?
Newly released from the bone marrow (RBC production site).
What are the names of two coagulation assays that are described as high volume because they are so frequently performed?
Prothrombin Time (PT) and Partial Thromboplastim Time (PTT)
Describe both the structure and the function of RBCs (red blood cells).
RBCs are anucleate (no nucleus) biconcave (concave on both sides) cells filled with a reddish protein, hemoglobin (Hb, HGB), which transports oxygen and carbon dioxide.
What are the defining characteristics of essential thrombocythemia?
Rare malignant condition characterized by extremely high platelet counts and uncontrolled platelet production
What characteristic of the RBC population is described by the MCV?
Reflects RBC diameter on a Wright-stained smear.
What is the primary physiologic function of PMNs?
Sole purpose is to engulf and destroy bacteria that have been earlier identified as harmful by the immune system.
What is the microscopic appearance of RBC's when stained with a Romanowsky stain?
Romanowsky is a Wright or Wright-Giemsa stain. RBCs appear pink to red and measure 7-8 μm in diameter w/ a zone of pallor covering 1/3 of their center, reflecting their biconcavity (Fig 1-1,A)
What is the relationship of band neutrophils to the left shift?
Signals a bacterial infection
What is the significance of an elevated mean platelet volume (MPV)?
Signals a regenerative bone marrow response to platelet consumption
What steps are included in the performance of a WBC differential?
Tabulate 100 WBC to determine % distribution
What characteristic of the RBC population is described by the MCH?
The MCH measures the amount of hemoglobin in a single RBC, reflects hemoglobin mass.
What is the purpose of using dilute acetic acid as a reagent when counting WBCs?
The acetic acid prevents RBCs from obscuring WBCs by lysing the RBCs.
What is an approximate normal range for the WBC count?
The approximate normal range for WBC count is 4,500-11,500/mcL.
What abnormal underlying condition or conditions may cause lymphopenia?
an abnormally low lymphocytes count associated with long-term drug therapy or immunodeficiency
Hematology is the study of:
blood cells
What is the function of platelets?
blood clotting
What is a moving average?
internal standard methodology.
What is included in a Complete Blood Count (CBC)?
is a group of tests that evaluate the cells that circulate in blood, including red blood cells (RBCs), white blood cells (WBCs), and platelets (PLTs).
What underlying abnormal conditions may induce neutropenia?
long term drug administration or viral infection
What is thrombocytopenia?
low platelet count
MCH
mean cell hemoglobin
MCHC
mean cell hemoglobin concentration
MCV
mean cell volume
Where do platelets come from?
megakaryocytes in bone marrow
What is the relationship of monocytes to macrophages?
monocytes are immature macrophages
What are the key morphologic features of lymphocytes on Wright-stained blood smears?
nearly round, slightly larger than RBCs, and have round featureless nuclei and a thin rim of nonglanular cytoplasm
What is the primary component of the granules of eosinophils?
proteins involved in immune system regulation.
What is the primary physiologic function of lymphocytes?
provide for host immunity
Erythrocytes
red blood cells
RDW
red cell distribution width
What do the measurement of cells and biological systems require?
requires elaborate calibration, validation, matrix effect examination., linearity, and reference interval. determinations.
What are the key morphologic features of monocytes on Wright-stained blood smears?
slightly larger diameter than other WBCs, blue-gray cytoplasm with fine azure granules.