Erythrocyte Lab Tests: Topic 1 Flashcards
what does CBC stand for?
complete blood count
what are CBCs used to determine?
- determine the status of our overall health
- diagnose medical conditions
- monitor medical conditions and treatments
what does CBC measure?
measures three main cell types within our blood
- red blood cells (RBCs)
- white blood cells (WBCs)
- platelets, which technically are cell fragments
what are the main components of the CBC?
- 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
what components of the CBC give us the big picture status of our RBCs?
red blood count, hemoglobin and hematocrit
what is the RBC count?
the number of red cells given as an absolute number per liter
what does the RBC count effect?
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.
what is erythrocytosis?
RBC count is higher than normal
what is anemia? how can you tell if someone has anemia from a CBC?
RBC count is lower than normal
can be determined by low RBC count, hemoglobin and hematocrit on CBC
what is hematocrit?
also known as the packed cell volume (PCV)
it’s the ratio of the volume of RBCs to the total volume of blood
what are the units of hemoglobin on a lab report?
grams/dL
what are the types of erythrocytosis?
- relative: an increase in RBC number without an increase in total RBC mass, usually due to loss in plasma volume
- absolute: an increase RBC numbers because of increased RBC mass
what is the mean corpuscular hemoglobin?
MCH
the average weight of hemoglobin per RBC
what is the mean corpuscular hemoglobin concentration?
MCHC
average concentration of hemoglobin per RBC
what is leukopenia?
low WBC count
when can leukopenia happen?
drug reactions, autoimmune disorders, cancer, and bone marrow disorders
what is leukocytosis?
high WBC count
when can leukocytosis happen?
drug reactions and leukemia
what is a WBC differential count?
tells us the amount of each type of white blood cell in the body
what is thrombocytosis?
too many platelets
can lead to excessive clot formation
what is thrombocytopenia?
too few platelets
can lead to increased bleeding
what is the mean platelet volume?
MPV
measures the average volume of platelets
what are the three followup tests if there’s an RBC abnormality on the CBC?
hemoglobin electrophoresis, osmotic fragility testing, and the direct antiglobulin test
what is hemoglobin electrophoresis?
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
what are the types of hemoglobin that show up on a Hb electrophoresis?
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)
what conditions can hemoglobin electrophoresis help identify?
thalassemia, sickle cell disease, sickle cell trait, and hemoglobin C disease
what causes thalassemia?
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
what is sickle cell disease?
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
what does osmotic fragility testing tell us?
tells us how easily our RBCs burst open when they are exposed to solutions of varying salt concentration
how do you conduct osmotic fragility testing?
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
when would a cell undergo hemolysis during osmotic fragility testing?
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
what is hereditary spherocytosis?
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
what disease is associated with increased osmotic fragility?
hereditary spherocytosis
what diseases are associated with decreased osmotic fragility?
sickle cell anemia and thalassemia
what does the direct antiglobulin test tell us?
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)
how does the DAT test work?
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
what conditions cause a positive DAT test?
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
what is autoimmune hemolytic anemia?
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
what is differential staining?
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.
what is the wright-giemsa stain?
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
what color do negatively charged compounds stain with the wright-giemsa stain? what are examples of negatively charged compounds? what are they called?
negatively charged compounds stain with methylene blue and are called “basophilic”
ex. DNA and RNA
what color do positively charged compounds stain with the wright-giemsa stain? what are examples of positively charged compounds? what are they called?
positively charged compounds stain red and are called “eosinophilic”
ex. hemoglobin
what are two types of stains?
- wright-giemsa stain
2. supravital stain
what are supravital stains used for?
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!!!
what is the reticulocyte count in anemia?
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
what is the mean corpuscular volume?
MCV
mean RBC size
what is the red cell distribution width?
RDW
the standard deviation of size from the mean
the higher the RDW, the larger the range of red blood cell sizes
what two indices tell us about the size of RBCs?
MCV and RDW
mean corpuscular volume: mean RBC size
red cell distribution width: the standard deviation of size from the mean
