Erythrocyte Lab Tests: Topic 1

Question 1

what does CBC stand for?

Answer 1

complete blood count

Question 2

what are CBCs used to determine?

Answer 2

1. determine the status of our overall health
2. diagnose medical conditions
3. monitor medical conditions and treatments

Question 3

what does CBC measure?

Answer 3

measures three main cell types within our blood

1. red blood cells (RBCs)
2. white blood cells (WBCs)
3. platelets, which technically are cell fragments

Question 4

what are the main components of the CBC?

Answer 4

• red blood cell count
• white blood cell count
• platelet count
• hemoglobin
• hematocrit

all of them: RBC count, hemoglobin, hematocrit, MCV, MCH, MCHC, RDW, WBC count, WBC differential, platelet count, and MPV

Question 5

what components of the CBC give us the big picture status of our RBCs?

Answer 5

red blood count, hemoglobin and hematocrit

Question 6

what is the RBC count?

Answer 6

the number of red cells given as an absolute number per liter

Question 7

what does the RBC count effect?

Answer 7

can directly affect the amount of oxygen our tissues receive because RBCs contain hemoglobin which is what carries oxygen to our tissues and participates in gas exchange

From the results of a RBC count, the physician can determine if our values are higher or lower than normal, which indicates erythrocytosis or anemia, respectively.

Question 8

what is erythrocytosis?

Answer 8

RBC count is higher than normal

Question 9

what is anemia? how can you tell if someone has anemia from a CBC?

Answer 9

RBC count is lower than normal

can be determined by low RBC count, hemoglobin and hematocrit on CBC

Question 10

what is hematocrit?

Answer 10

also known as the packed cell volume (PCV)

it’s the ratio of the volume of RBCs to the total volume of blood

Question 11

what are the units of hemoglobin on a lab report?

Answer 11

grams/dL

Question 12

what are the types of erythrocytosis?

Answer 12

1. relative: an increase in RBC number without an increase in total RBC mass, usually due to loss in plasma volume
2. absolute: an increase RBC numbers because of increased RBC mass

Question 13

what is the mean corpuscular hemoglobin?

Answer 13

MCH

the average weight of hemoglobin per RBC

Question 14

what is the mean corpuscular hemoglobin concentration?

Answer 14

MCHC

average concentration of hemoglobin per RBC

Question 15

what is leukopenia?

Answer 15

low WBC count

Question 16

when can leukopenia happen?

Answer 16

drug reactions, autoimmune disorders, cancer, and bone marrow disorders

Question 17

what is leukocytosis?

Answer 17

high WBC count

Question 18

when can leukocytosis happen?

Answer 18

drug reactions and leukemia

Question 19

what is a WBC differential count?

Answer 19

tells us the amount of each type of white blood cell in the body

Question 20

what is thrombocytosis?

Answer 20

too many platelets

can lead to excessive clot formation

Question 21

what is thrombocytopenia?

Answer 21

too few platelets

can lead to increased bleeding

Question 22

what is the mean platelet volume?

Answer 22

MPV

measures the average volume of platelets

Question 23

what are the three followup tests if there’s an RBC abnormality on the CBC?

Answer 23

hemoglobin electrophoresis, osmotic fragility testing, and the direct antiglobulin test

Question 24

what is hemoglobin electrophoresis?

Answer 24

gives us an in-depth look at the amount and type of hemoglobin within our RBC

If we apply electrical charge to a gel that contains hemoglobin samples, different hemoglobin types migrate away from the negatively charged electrode, landing at various distances away from their point of origin

+ “A Fat Santa Clause” -

A: normal Hb B chain
F: normal Hb γ chain
S: sickle cell Hb B chain
C: hemoglobin C B chain

Question 25

what are the types of hemoglobin that show up on a Hb electrophoresis?

Answer 25

A: normal Hb B chain (HbA adult) F: normal Hb γ chain (HbF, fetal) S: sickle cell Hb B chain (HbS) C: hemoglobin C B chain (HbC)

Question 26

what conditions can hemoglobin electrophoresis help identify?

Answer 26

thalassemia, sickle cell disease, sickle cell trait, and hemoglobin C disease

Question 27

what causes thalassemia?

Answer 27

caused by decreased production of either alpha or beta globin chains degree of impairment and severity varies according to the specific genetic mutation that is present, and the number of genes that are affected

Question 28

what is sickle cell disease?

Answer 28

a mutation in the beta chain gene causes hemoglobin to polymerize when it deoxygenates, turning the normal biconcave-disc-shaped of RBCs into a crescent moon, or sickle, shape these sickled cells can get stuck in blood vessels, impairing oxygen delivery to tissues and causing pain and other problems in organs, muscles, and bones

Question 29

what does osmotic fragility testing tell us?

Answer 29

tells us how easily our RBCs burst open when they are exposed to solutions of varying salt concentration

Question 30

how do you conduct osmotic fragility testing?

Answer 30

the patient’s blood is added to various saline solutions with progressive concentrations of NaCl the amount of cell lysis (hemolysis) is plotted against NaCl concentration if the RBCs lyse when the solution is not very hypotonic then they are considered fragile

Question 31

when would a cell undergo hemolysis during osmotic fragility testing?

Answer 31

if a cell is placed in a hypotonic solution, water will enter the cell (because the cell has more solute than the surrounding solution), causing swelling of the cell and, eventually, lysis as the concentration of NaCl in the saline solution increases, the lysis of the RBCs will decrease

Question 32

what is hereditary spherocytosis?

Answer 32

A disease process frequently associated with increased osmotic fragility = RBCs lyse when the solution is not very hypotonic The spherocytes in hereditary spherocytosis are less flexible than normal RBCs, due to cytoskeleton mutations; this makes them more prone to rupture they're so sensitive to blood tonicity that they even lyse at higher than normal concentrations of NaCl

Question 33

what disease is associated with increased osmotic fragility?

Answer 33

hereditary spherocytosis

Question 34

what diseases are associated with decreased osmotic fragility?

Answer 34

sickle cell anemia and thalassemia

Question 35

what does the direct antiglobulin test tell us?

Answer 35

DAT aka Coombs test tells us whether the patient’s RBCs have been coated with antibody or complement (a phenomenon which happens in autoimmune hemolytic anemias and in other clinical settings)

Question 36

how does the DAT test work?

Answer 36

anti-Ig antibody (or Coombs reagent) is added to the patient’s RBCs Coombs reagent is actually a combination of immunoglobulins directed against both human antibodies and complement If the patient’s RBCs are coated with immunoglobulin (or complement), they will agglutinate, and the test will be considered positive

Question 37

what conditions cause a positive DAT test?

Answer 37

A positive DAT may be seen in autoimmune hemolytic anemia, hemolytic transfusion reactions, hemolytic disease of the fetus and newborn, and drug- induced immune hemolysis aka the patients RBC are coated with immunoglobulin

Question 38

what is autoimmune hemolytic anemia?

Answer 38

the body makes antibodies that bind to RBCs, causing them to lyse and making them susceptible to phagocytosis by splenic macrophages. you will get a positive DAT test for people with AIHA

Question 39

what is differential staining?

Answer 39

a process which uses two or more dyes that stain some structures one color and others a different color, allowing you to visualize different structures more easily Using more than one stain can help the viewer better differentiate between organisms and cellular components The differential staining of blood cells allows the different types of WBCs to be visualized.

Question 40

what is the wright-giemsa stain?

Answer 40

the most commonly-used differential stain for blood specimens consists of a combination of eosin, which stains cellular structures red, and methylene blue, which stains cellular structures blue

Question 41

what color do negatively charged compounds stain with the wright-giemsa stain? what are examples of negatively charged compounds? what are they called?

Answer 41

negatively charged compounds stain with methylene blue and are called “basophilic” ex. DNA and RNA

Question 42

what color do positively charged compounds stain with the wright-giemsa stain? what are examples of positively charged compounds? what are they called?

Answer 42

positively charged compounds stain red and are called “eosinophilic” ex. hemoglobin

Question 43

what are two types of stains?

Answer 43

1. wright-giemsa stain | 2. supravital stain

Question 44

what are supravital stains used for?

Answer 44

commonly used to detect reticulocytes (immature RBCs) A drop of blood is stained with new methylene blue or brilliant cresyl blue, and the *ribosomal rRNA* in reticulocytes stains a deep blue color, making the reticulocytes easy to visualize ribosomal rRNA is what's visible!!!

Question 45

what is the reticulocyte count in anemia?

Answer 45

reticulocyte = immature RBC Counting the number of reticulocytes can provide insight on bone marrow activity and disorders such as anemia In anemia, the reticulocyte count is often increased because the bone marrow is producing more RBCs to make up for the ones that are lost

Question 46

what is the mean corpuscular volume?

Answer 46

MCV mean RBC size

Question 47

what is the red cell distribution width?

Answer 47

RDW the standard deviation of size from the mean the higher the RDW, the larger the range of red blood cell sizes

Question 48

what two indices tell us about the size of RBCs?

Answer 48

MCV and RDW mean corpuscular volume: mean RBC size red cell distribution width: the standard deviation of size from the mean