Topic 4: Anemias Putting it Together Flashcards
what lab values of a CBC should you look at if you suspect someone has anemia?
hemoglobin then mean cell volume (MCV)
low Hb = anemia
MCV tells us if anemia is microcytic, normocytic or macrocytic
which anemias are microcytic?
- iron-deficiency anemia
- thalassemia
- sometimes anemia of chronic disease (ACD)
which anemias are macrocytic?
- megaloblastic
2. non-megaloblastic anemia
what deficiency causes megaloblastic anemia?
B12/folate deficiency
what will the blood smear of a megaloblastic anemia look like?
it will show big oval macrocytes and hypersegmented neutrophils
what will the blood smear of a no-megaloblastic anemia look like?
Non-megaloblastic anemias are still macrocytic, but they don’t have the crazy megaloblastic changes, so we won’t see hypersegmented neutrophils in the blood
alcohol or myelodysplasia can cause anemia that falls into this category
what two things can induce non-megaloblastic anemia?
- alcohol
- myelodysplasia
clonal disorder where all the cells arise from one initial bad cell that can sometimes turn into leukemia
what’s a common characteristic of normocytic anemias?
they’re usually hemolytic!
the red blood cells (RBSs) are getting busted open for some reason
If we have a normocytic anemia, what lab test will tell us whether the bone marrow is responding appropriately?
reticulocyte count
most patients with hemolytic anemias have a robust bone marrow response to the anemia
the erythroblasts are dividing like crazy and maturing into RBCs to send into the periphery so there’s an increased reticulocyte count
When the bone marrow is responding to the anemia by creating more RBCs, the reticulocyte count goes up. If the bone marrow isn’t working well, the reticulocyte count will be normal or decreased.
what is aplastic anemia?
the bone marrow is basically making nothing—no RBCs, no white cells, no platelets
the blood reflects this by being pancytopenic
what CBC value is used to differentiate between iron-deficiency anemia and thalassemia
both are microcytic anemias and blood smears can look similar so use the RBC distribution width (RDW) = measures how much the cells vary in size
IDA: RDW is elevated because as each new wave of iron-starved RBCs reaches the blood, it is smaller than the last wave so there’s a bunch of newer little RBCs and then normal sized older RBCs
thalassemia: RDW is normal because thalassemia is not an evolving thing, like IDA. You’re born with the defect, and every time you make a new RBC, you’re dealing with the same defect. So the cells are all the same size
What two CBC parameters help you differentiate between IDA and thalassemia? (aka microcytic anemias)
- RDW
- RBC count
RDW (increased in IDA, normal or low in thalassemia) and RBC count (decreased in IDA, increased in thalassemia)
how can the RBC count help you differentiate between IDA and thalassemia microcytic anemias?
IDA: low RBC count because you don’t have enough iron to make red blood cells, so the count goes down
thalassemia: increased RBC count because it may be the bone marrow’s way of dealing with the lack of globin chains – maybe it makes smaller, but more numerous, RBCs
how can you differentiate between IDA and thalassemia on a blood smear?
- thrombocytosis, which is often present in IDA, but not in thalassemia;
- elliptocytes (or cigar-shaped cells, if you like a smooth Cohiba), which are
present in IDA but not thalassemia - basophilic stippling, which may be seen in thalassemia but not in IDA
what kind of anemia is anemia of chronic disease?
ACD can be normocytic, but it can be microcytic, too
how do you differentiate between ACD and IDA?
iron studies
- serum iron is low in both so that doesn’t help
- low ferritin = IDA for sure
normal/high ferritin = probably ACD but it could still be IDA because ferritin is an acute phase reactant, it will go up when there are things like inflammation around
- TIBC is increased in IDA and normal/decreased in ACD
* ferritin = body’s iron stores
How do we use the ferritin to distinguish IDA from ACD?
ferritin should be low in IDA and normal to high in ACD.
however, ferritin is an acute reactant – so a normal or even increased ferritin does not rule OUT IDA.
what RBC size category of anemias do hemolytic anemias usually fall into?
usually normocytic anemias
how can you tell if a patient is actually hemolyzing their RBCs?
- elevated bilirubin
- elevated lactate dehydrogenase
- decreased free haptoglobin levels
- hemoglobin in the serum or urine if hemolysis is intravascular
- increased reticulocytes in the blood smear
- nucleated RBCs in blood smear if there’s severe anemia
how do bilirubin levels change during hemolytic anemia?
usually elevated
you’re dumping all that heme into the blood, and it’s got to be broken down into bilirubin
If it’s a rip-roaring hemolysis, the liver will not be able to keep up, and we’ll see an unconjugated hyperbilirubinemia
how do lactate dehydrogenase levels change during hemolytic anemia?
usually elevated
LDH is just an enzyme that’s present in a lot of cells, including RBCs
if you bust the RBCs open, LDH leaks out and can be measured in the blood
how do FREE haptoglobin levels change during hemolytic anemia?
decreased haptoglobin
haptoglobin carries free hemoglobin
so as more and more hemoglobin is dumped into the blood, the amount of free (unbound) haptoglobin decreases
how do hemoglobin levels in the serum and urine change during hemolytic anemia?
might also see hemoglobin in the serum (hemoglobinemia) or urine (hemoglobinuria) if the hemolysis is intravascular
how can you look at a blood smear to tell if it’s a hemolytic anemia?
look at the blood smear for presence of reticulocytes, and—if it’s a particularly severe anemia—nucleated red blood cells
reticulocyte count should go up assuming the bone marrow is working properly
in severe cases of anemia, the marrow lets nucleated RBCs leave home early to make room for more cells to divide
what are the two categories of hemolytic anemias?
autoimmune hemolytic anemia
non-immune hemolytic anemia
what test would tell you if it’s an autoimmune hemolytic anemia or non-immune hemolytic anemia?
direct antiglobulin test (DAT)
looks to see if the patient’s RBCs are coated with antibody
if it’s positive, it’s probably an autoimmune hemolytic anemia
if it’s negative, it’s one of the (many) non-immune hemolytic anemias
what shows up in the blood smear of non-immune hemolytic anemias that can help differentiate them?
- schistocytes, in microangiopathic hemolytic anemia
- spherocytes, in hereditary spherocytosis
- bite cells, in G6PD deficiency
- sickle cells in sickle cell anemia
how can macrocytic anemias often be differentiated?
by looking for megaloblastic changes on a blood smear
how can microcytic anemias often be differentiated?
can be differentiated using:
- the RDW and RBC count for IDA and thalassemia
- iron studies for IDA and ACD
- blood smear (look for clues like elliptocytes)
what’s in the blood smear of a microangiopathic hemolytic anemia that differentiates it from the other hemolytic anemias?
schistocytes
what’s in the blood smear of hereditary spherocytosis that differentiates it from the other hemolytic anemias?
spherocytes
what’s in the blood smear of a G6PD deficiency anemia that differentiates it from the other hemolytic anemias?
bite cells
aka RBC with semicircular “bites” at the edges
what’s in the blood smear of sickle cell anemia that differentiates it from the other hemolytic anemias?
sickle cells
a woman has low Hb, low MCV, high RDW, low RBC count, and high platelets. Blood smear has increased anisocytosis and elliptocytes. What anemia does she have?
iron-deficiency anemia
low Hb = anemia
low MCV = microcytic anemia
increased RDW = iron-defieincy
a female of childbearing age with a microcytic anemia, iron-deficiency anemia due to heavy periods or multiple pregnancies is the presumed diagnosis
woman has low Hb, high MCV, normal RDW, low RBC count. Blood smear has hyperhsegmented neutrophils. What anemia does she have?
low Hb = anemia
high MCV = macrocytic anemia
hypersegmented neutrophils = megaloblastic anemia
patient is jaundiced. Low Hb, normal MCV, normal RDW, low RBC count, normal WBC, normal platelets. Blood smear shows RBCs with semicircular bites at the edges. What anemia does he have?
G6PD deficiency
patient has petechiae across both legs and trunk. low Hb, normal MCV and RDW. low RBC count, WBC, and platelets. Blood smear shows decreased number of normal looking RBC and few WBC and platelets. what anemia does she have?
aplastic anemia
CBC shoes a decreased in all three cell lines: RBC, WBC, and platelets