A. MCV < 80: Microcytic anemia’s: Fe def = MC and Anemia of chronic dz, thalassemias, sideroblastic anemias
B. MCV > 100: Macrocytic anemia’s: B12/Folate def = MC; usually folate def in an alcoholic C. MCV 80-100: Normocytic anemia’s: low reticulocyte ct corrected: aplastic anemia, renal dz; high corrected reticulocyte ct: hemolytic anemias – hereditary spherocytosis, sickle cell, G6PD def, autoimmune hemolytic anemia, microangiopathic
II. Reticulocyte count: Reticulocyte count next to CBC is the first step in the work up of any anemias. What is reticulocyte? Young RBC. In 24 hrs, a reticulocyte will become a mature RBC with a biconcave disk.
If you have an anemia, the reticulocyte count is imp b/c it tells you where the problem is: is the prob in the BM in making the RBC, or is it a prob outside the BM causing the problem? To determine this, look at reticulocyte ct. If the BM was the prob, then the reticulocyte ct would not have an appropriate response. What is an appropriate response? You would have a BM with hyperplasia, that has rev’d itself up, and making RBC’s and should be putting reticulocytes out prematurely, therefore working correctly to correct the anemia. Therefore, it tells whether the BM is responding appropriately or not. If you have blood loss right now, do not expect
reticulocyte ct to be elevated in 24 hrs; it takes at least 5-7 days to get the response of making more reticulocytes (like the kidney making bicarb, which takes a few days (3-4) to make). If nothing is wrong with the BM, then it should host a normal reticulocyte response; if there is something wrong, will not have a normal response (imp b/c might decide whether you have to do a BM exam or not). Therefore, if you have a normal reticulocyte ct, do not do a BM exam.
Have to correct the reticulocyte count for the degree of anemia.
Corrected reticulocyte ct = Hct of the pt ÷ 45 × reticulocyte ct that you are given
Example: pt’s Hct is 15% (which is very severe anemia), and the reticulocyte ct that was initially measured is 9% (which is increased – anything over 3% is increased).
This ‘looks’ like the BM is responding correctly b/c the ret ct is 9% (but have to correct for the degree of anemia). 15/45 X 9 is 3; so, when we correct for the anemia, we have 3%; that’s what the corrected is – therefore, 3% or greater = good response; 3% or less = bad response;
so, this figure is saying that it is a reasonable response occurring in the pt.
Slide of a reticulocyte (know what it looks like)
4. Reticulocyte stain
– need to do a special giemsa stain to see the black filaments (which are RNA filaments); b/c they are RNA filaments, the reticulocyte is still synthesizing Hb. So, in about 24 hrs, 25% the normal Hb is being synthesized and need RNA filaments; cannot see these without doing a special stain (look like little black worms in the RBC – do not confuse with Heinz body).
Another slide using right giemsa stain of reticulocyte with bluish stain – polychromasia. These are younger blood cells than the 24 hr old reticulocytes. They still have the basophilia, which is not normally present in the peripheral blood; so, when we see them, it means that the BM is
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really responding, and pushing even the younger ones out. Therefore, whenever the boards say’s ‘polychromasia’, they are talking about these cells and these cells take 2-3 days before they become a mature RBC. Why is this imp? B/c we have to make an additional correction – why? When we are working up an anemia, we do a corrected ret ct and want to know how the BM is responding right now at this day. Not interested about what will happen in 2-3 days, but what will happen right now. Here’s the prob: when they do a reticulocyte stain, these guys will also have RNA filaments and will be counted in the ret ct and it will show a falsely elevated ret ct (we don’t want these b/c they take 2-3 days b4 they become a mature RBC) instead we want the normal guys there. So, how do we factor them out? Divide by 2. So, make the first
correction for the degree of anemia (did it with 3% in this case), look at CBC and see nothing that says polychromasia. Let’s say the CBC ct says ‘polychromasia present’ – then have to make an additional correction by dividing by 2. All of a sudden, it is now 1.5% and this is not a good reticulocyte response! So, when you see the term “polychromasia”, then you have to make an additional correction by dividing by 2.
Example: reticulocyte – cannot see with right giemsa stain; use special giemsa stain to see RNA filaments, and ribosomes (look like dots – BASOPHILIC STIPPLING, seen in lead poisoning).
III. Side notes:
When looking at CBC you can make many dx’s.
Rule of 3 is good: Hb x 3 should roughly equal the Hct
Example: for previous ie, had 15% Hct, therefore the Hb was a 5
Transfusion of packed RBC’s – for every unit transfused increase the Hb by 1 and the Hct by 3%. Example: pt with 5 gram Hb, and given 3 units of packed RBC’s. The following day the Hb is 6 and the Hct is 18, is that an appropriate response? NO, it should’ve been 8, with Hct of 24.
It wasn’t 8 b/c the pt has a GI bleed (pt was bleeding).
MCC anemia worldwide = Fe def anemia MCC cause of Fe def (overall) = GI bleed
Therefore, the MC reason why Hb and Hct don’t go up after transfusion is b/c blood loss, MC due to GI tract bleed.
IV. RBC indices – MCV – how big is the cell? Best way to classify is with MCV (mean corpuscular volume) Small, normal or big? The machine has the RBC’s pass through an aperture and sizes it.
And then takes an average; this is the best way for classifying an anemia MCV: < 80, it is microcytic (if you play odds, its Fe def)
MCV (normal): 80 -100 =; have Normocytic anemia;
MCV above 100 = macrocytic (b12 or folate)
If you have small and large cells (dimorphic popcorn of RBC’s) it will be Normocytic
(Like the met acidosis, and resp alk, but normal pH). So, how could you have a Fe def anemia and a folate def anemia at the same time? Know where these things are reabsorbed – Fe reabsorbed in the duodenum, Folate is reabsorbed in the jejunum, and B12 is reabsorbed in the terminal ileum. So if you have all these, you have small bowel dz (ie celiac dz); pt has
malabsorption that affects diff areas of the bowel. Example: celiac sprue (MCC malabsorption) – involves duodenum and jejunum, therefore will have def of Fe and folate, and will have small cells and large cells. Example: if it involves the jejunum and terminal ileum, you will have folate and B12 def.
V. RDW – RBC Distribution Width
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This machine looks at the RBC’s and tells if the RBC’s coming out of the aperture are all uniformly small, normal, macrocytic, or different in size. So, the RDW detects a change in size of the RBC’s and it reports it as a number. Example: microcytic anemia, with an increased RDW; this tells us that is microcytic, and there are different sized microcytic cells. Example: if you develop microcytic anemia overnight and all the cells are Fe def, the cells don’t become microcytic immediately; they are normocytic first before they become microcytic, and there will be a size variation picked up by the RDW.
Here’s the trick: when you look at the CBC, and it shows decreased MCV with an increased RDW, this is Fe def anemia (not thalassemias b/c that is genetic and ALL the cells are microcytic).
Slide with high RDW – has large and small cells. Another slide with spherocyte (have too little membrane, and therefore cannot hold a biconcave disk - an anorexic cell), and target cell (has too much membrane and too much Hb collects in there and looks like a bull’s-eye – an obese cell). Target cells are imp markers for alcoholics b/c they have altered cell membrane due to an altered cholesterol concentration of the membrane and markers for hemoglobinopathies (ie thalassemias, SCD, HbC).
Mature RBC looks like biconcave disk and is thin in the middle b/c there is less Hb there, and more is concentrated at the edges; this is why there is a central area of pallor in a normal RBC when it lying flat.
1. Normal PB smear and schematic of mature RBC
All microcytic anemias have one thing in common: decreased Hb synthesis; with less Hb, the redness of the cell with decrease and see greater area of pallor will increase (and if you play odd it’s IDA).
2. Asymptomatic patient
Spherocyte – too lil mem, therefore it’s a sphere; NO central area of pallor! (All red, no central area of pallor).
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3. Supravital stain of RBCs in an asymptomatic person
Microcytic anemias all have a PALE, blank color to them; therefore, it is very easy to ID spherocyte and microcytic cells with hypochromia and IDA of chronic dz.