- Hello, everyone.
Thank you for joining me.
My name is Sanjay Saint,
and I am here to talk to you about anemia.
This comes from the Saint-Chopra Guide
to Inpatient Medicine, so if you like the video,
there'll be a slide at the end
with some information on how to actually get the book.
So, first, let's define anemia.
It's defined as a reduced absolute number
of circulating red blood cells.
In men, a hematocrit less than 41% defines anemia,
or if you prefer to use hemoglobin,
which is roughly 1/3 of the hematocrit,
it's a hemoglobin less than 13.5,
and in women, it's a hematocrit less than 36%
or a hemoglobin less than 12.
Anemia is not a disease.
Rather, it's a manifestation of an underlying disease,
and our goal is to figure out
what that underlying disease is.
The best approach is to look at the mean corpuscular volume,
or MCV, break it up into low, high, and normal,
and then have a differential diagnosis
for each one of those categories.
So, let's first focus on microcytic anemia,
MCV less than 80, and for all of these,
I'm assuming that the RDW is normal,
which means that there isn't much variability.
If the RDW is elevated,
that tells you that there may be populations of cells
that are large, some that are small,
and so the actual MCV could be normal,
but actually, we could be missing both microcytic
as well as macrocytic anemia.
But for the sake of this discussion,
let's just assume the RDW is normal.
There are four main causes of microcytic anemia,
and before I give them to you, you may wanna pause
and just think what those four are in your head.
Let me tell you.
They're iron deficiency anemia,
which is the most common nutritional deficiency in the world
and one of the most common causes of microcytic anemia,
if not the most common cause.
And once you make the diagnosis of iron deficiency anemia,
you can't just stop there.
You have to figure out what's the underlying cause
of iron deficiency.
In a non-menstruating patient,
you must rule out underlying GI blood loss,
specifically due to colorectal cancer.
A second cause is thalassemia,
and usually we reply upon
hemoglobin electrophoresis for that,
but you can also look at the thalassemia index,
which is MCV over RBC count
to give you a clue if the patient has thalassemia.
If the MCV over RBC count is greater than 13,
it's more likely to be iron deficiency anemia.
If it's less than 13, then it's consistent with thalassemia.
The third cause of microcytic anemia
is anemia of active inflammation
or anemia of chronic disease,
so this would be anemia due to certain types of malignancies
or inflammatory disorders, such as lupus or vasculitis
or sarcoidosis, or even anemia of chronic disease,
things that you don't think of being inflammatory,
but like diabetes mellitus or congestive heart failure
can also give you anemia of inflammation.
And then, finally, sideroblastic anemias,
which are due to either you can be born with these
or it could be your drugs and toxins, like alcohol,
or certain malignancies.
The key thing is to distinguish iron deficiency anemia
from these others, and usually what we do is
we look at iron studies, but the key iron study
that we would look at would be the ferritin.
If the ferritin is less than 12,
it almost guarantees that the patient
has iron deficiency anemia,
and then we have to figure out what the underlying cause is.
As the ferritin increases, if it's greater than 200,
for the most part, it rules out iron deficiency anemia,
but depending on what the underlying problems are,
sometimes the ferritin, if it's 35 or 50 or 100,
then we may have to do further testing to see
if the patient has iron deficiency anemia.
The next is macrocytic anemia.
There's six big causes of macrocytic anemia.
This is where the MCV is more than 100.
Again, you may wanna pause and think about what these are,
and they are the following.
So, megaloblastic anemias.
These are anemias that show neutrophils
that are hyper-segmented, six or more segments.
The most common causes of these
would be vitamin B12 deficiency.
It also gives you neurological problems.
Folate deficiency,
that does not give you neurological problems.
Certain drugs, especially chemotherapeutic agents,
and miscellaneous causes,
such as inborn errors of metabolism,
which usually present in children rather than adults.
Other causes of macrocytic anemia include
chronic liver disease, alcohol intake,
hypothyroidism, reticulocytoses,
because reticulocytes are large,
and myelodysplasia, which is really a pre-leukemia
that occurs in elderly patients
that can predispose to frequent infections.
The Pelger-Huet abnormality
or the pseudo-Pelger-Huet abnormality
is what you see on neutrophils.
It's bilobed nuclei on the neutrophil,
and it's in a patient who could have other types
of CBC abnormalities, such as thrombocytopenia as well,
and you need a bone marrow to confirm that.
So, once you have this list,
you can then do all the necessary testing
to rule in or rule them out.
And then, finally, we'll end with normocytic anemia,
and this is where the MCV is between 80 and 100,
and we begin with the Reticulocyte Index,
and there's easy calculators to use,
because that takes into account what the hematocrit is
and the maturation factor,
and we break it up into a Reticulocyte Index
that shows that there's a proliferative anemia,
which the Reticulocyte Index is greater than two,
or a non-proliferative anemia, where it's less than two.
And then we would use the following algorithm.
So, let's say we do the Reticulocyte Index.
It's high, greater than two.
We call this proliferative.
This usually is due to red blood cell loss.
Either the patient is hemorrhaging somewhere,
they could be hemorrhaging in the GI tract,
which is the most common place,
or it could be into the lungs or into the bladder,
or if they've just had a heart catheterization,
so it could be bleeding into the groin or the thigh.
Usually, you gotta find it and fix it.
The next is hemolysis, and this could be a little trickier.
Clues that a patient is hemolysing is that they'll have
an elevated LDH, elevated indirect bilirubin,
and a low heptoglobin.
And once you think someone is hemolysing,
then you must look at the smear.
Depending on what the smear shows,
you either know what it is, like if you see sickle cells,
it's sickle cell anemia,
or you can do the next appropriate test,
so let's say if you see schistocytes,
which are fragments or red cells,
that's called MAHA, or microangiopathic hemolytic anemia.
We then check a PT and PTT.
If that's elevated, you're dealing with DIC,
which could be due to sepsis or trauma
or an OB complication,
but if the PT/PTT are normal,
then we're dealing with all the non-DIC causes of MAHA,
such as heart valve abnormalities,
a mechanical aortic valve, for example,
HUS/TTP, hemolytic-uremic syndrome or TTP, vasculitis,
severe hypertension can do it,
and also HELLP, hemolysis, elevated liver test,
and low platelets, which is seen is obstetric patients.
But let's say you see spherocytes,
and the spherocytes then,
the next step is to do a Coombs' test.
If that Coombs is positive,
the answer is auto-immune hemolytic anemia.
If it's negative, then you think about
hereditary spherocytosis or paroxysmal cold hemoglobinuria.
Usually, when I'm thinking that a patient is hemolysing,
I get a hematologist involved to help me with the diagnosis.
But going back up to the Reticulocyte Index,
if that's low, we call that hypoproliferative,
and then we check a white count and a platelet count.
If those are also low, we call this pancytopenia,
and pancytopenia is usually either due to hypersplenism,
which gives you a mild to moderate pancytopenia,
so you do a CT or ultrasound to rule that out,
but more likely than that,
it's due to a bone marrow process,
and the bone marrow process can either be due to
a nutritional deficiency, such as B12 or folate deficiency,
or it could be due to malignancy,
something that's invading the bone marrow,
known as mylophysic disorder, such as tuberculosis
or fungal disorders, or it could be due to aplastic anemia,
which could be idiopathic, or it could be to drugs
and toxins or viruses.
Usually, after we rule out the patient having a big spleen,
we do a bone marrow biopsy if the patient has pancytopenia.
But most of the time, fortunately,
in someone who has a low reticulocyte count
and normocytic anemia, the white count and platelet count
would be normal or elevated,
in which case, we're left with anemia of chronic disease
or active inflammation, which can give you
either a microcytic anemia, as we discussed,
or a normocytic anemia, the anemia of renal disease
because of decreased production of erythropoietin,
or finally, pure red cell aplasia,
which can be associated classically with thymoma,
or if they show you a chest X-ray on the boards
or the shelf exam with an anterior mediastinal mass
in a patient with a low retic count, a normocytic anemia,
you should think that that could be pure red cell aplasia.
So, some final points about anemia:
anemia is not a disease.
It's a clinical manifestation of an underlying disease.
Our job is to figure out what that underlying disorder is,
and we use the MCV to help us,
microcytic anemia, macrocytic anemia, and normocytic anemia.
And then, the treatment depends on the underlying diagnosis,
and this is where reading textbooks
and the Saint-Chopra Guide can help you with next steps.
So, thank you for listening.
Again, if you like this,
please feel free to purchase the Saint-Chopra Guide,
and you can use the promotion code that's on your screen.
Have a good day, bye.