There are only 3 backbone categories of the complete blood count(cbc), or 3 numbers we care about:

• White Blood Cell (WBC)
• Hemoglobin (hg)
• Platelets (plt)

The rest of the categories reported on the CBC, things like RBCs or MPV, are only there to help further flesh out problems with one of the 3 backbone categories (aka we get to ignore them!)

WBC

Normal range is between 4-10, depending on gender

Causes of elevated WBC include:

• Infection
• Demargination
• Trauma or physical stressors
• Activation of inflammatory response
• Catecholamines

You’ll notice there are two kinds of differentials. An Automatic differential done by the machine and a manual differential, where someone looks under the microscope to see all the differences in each WBC type and categories it for you.

Left shift = bandemia

If you see the graph on the handout you can see multiple curves on the graph. One is labelled normal, that is where the normal amount of cells are found. if there is an over abundance of cells that are hyper segmented it shifts the graph to the right. This happens in pernicious anemia. If however if there is in increase in younger cells, also known as bands, there will be a left shift. This can also be called bandemia.  This happens during infection, when the marrow allows the young soldiers out early to help in reinforcements but also in leukemia. So to be clear, left shift and bandemia are the same, and this has more to do with the age of the cells rather than the number. 

Other than that quick backtstory to each.

• Neutrophils (ANC) are high in acute phase reactions and bacterial infections. They are also high in demargination or physical stressors. They are most famously low in chemo and should be looked at when identifying neutropenic fever.
• Lymphocytes include B cells & T cells & NK cells. High mean viral infection, autoimmune, leukemia or vaccination. Low can mean radiation exposure, certain viruses (like full blown AIDS).
• Monocytes go into the tissue and become macrophages. They can be high in chronic inflammation or long term stressors. 
• Eosinophils are most responsible for parasitic infections & are also  involved in certain autoimmune diseases or allergic reactions- but not others.
• Basophils stain basic blue color and are similar to mast cells. They are usually present during chronic inflammation/allergies like asthma or macroparasites like tapeworms.

RBCs

Next backbone of the cbc is Hemoglobin. Now i’m sure you noticed I said Hemoglobin and not hematocrit. I want to address why? So HCT is measured when a test tube of blood is centerfuged, and parts of blood separated into 3 different parts: serum, white or buffy coat & the RBCs in the bottom. The others aren’t important right now but that bottom part is measured as a percetage of the total amount of fluid in the tube, that percentage is The HCT. whereas the hemoglobin is actually measured by the machine, the number of proteins we can actually find. Hct is much more old school and crude than Hg although both of these numbers are equally as accurate–  most folks learn by getting comfortable with just one and Hg is more sophisticated -so that’s what we do. 

First polycythemia or high Hg causes. As you can imagine there are some very distinct causes for this:

• dehydration also known as hemoconcentration.
• chronic state of hypoxemia like COPD, OSA, congenital heart disease or high altitude
• polycythemia vera

Low Hg or anemia has multiple categories. The good news is once Hg gets below 7.0 that’s when we start transfusion regardless of cause.

If MCV is less 80 meaning low, most likely you have a microcytic anemia (aka small cell low Hg) cause by iron deficiency anemia. 

• Without even doing Iron studies this is the most common of all causes of anemia. 
• thalassemia or sickle cell anemia. 
• anemia of chronic disease- this encompasses things like kidney disease (when the kidneys quit making erythropoietin which stimulates the bone marrow) 

If the MCV is high ( which means over 100) its a macrocytic anemia. 

• folate or vit b12 deficiency (often alcoholism)
• drug induced anemia (seizure meds, etc)

Lastly we have normal MCV anemia

• hemorrhage. 
• myelodysplastic disorders ex. aplastic anemia or parvob19 infections

RBC morphology:

• Tear drop (dacrocytes)- when bone marrow is infiltrated (infxn, Cancer, scarring)
• Schistocyte- RBC fragments (usually hemolytic anemia)
• Target cells (codocytes) – post splectomy, liver dz, Iron def, lipid dz, thalassemia
• Sickle cells – almost exclusively sickle cell anemia. 
• Burr cell (echinocytes) – even projections all over cell, evenly spaced, caused by renal disease or can be artifact when looking at the slide
• Spur cells (acanthocyte) – are cells with spurs but they are not evenly spaced, liver disease not by artifact
• Howell Jolly Bodies- are remnants of the nucleus of the RBC, remember they aren’t supposed to have a nuclues. These are usually removed by the spleen, so we see Howell Jolly bodies in folks who don’t have a spleen that is functioning.
• Blast cells- just like bands in WBC, blasts are large baby RBCs. If there are lots of blasts in the blood it means they could be recovering from anemia of some kind.

Platelets

They are just fragments from a giant cell in the bone marrow called a Megakaryocyte. Their only job is to stick together and clot when needed. Normal is from 100,000-350,000.

High platelets = thrombocytosis = over 450,000 but nobody really cares about it until its over 750,000 if then. 

• “reactive platelets”- where something is happening in your body to activate the inflammatory or coagulopathic pathway. For example, hemorrhage, iron deficiency anemia, splenectomy
• leukemias esp. CML & AML

Low platelets = thrombocytopenia = less 50,000

• Transfusing platelets at less 20,000
• Spontaneous bleeding starts around 10,000. 
• Cirrhosis or liver disease.
• Heparin Induced Thrombocytopenia(HIT), snake bites, lyme disease and leukemias.
• g DIC or HELLP Syndrome
  • ITP – also known as idiopathic thrombocytopenic purpura (say that 10 times fast!) this is a low platelet for an unknown reason
  • TTP – Thrombotic Thrombocytopenic Purpura- T It is defined by a pentad: fever, anemia, thrombocytopenia, AKI, AMS. This is the disease that we do NOT want to infuse platelets because it makes it worse. 

Why is my sample coming back hemolyzed? 

To answer this quickly: hemolyzed means the RBCs have burst, spilling their contents into the system and falsely elevating the K. This effects how the machine reads all other measurements and means we have to send a new sample. One way to falsely have hemolysis read is if someone’s bilirubin levels are high. 

Another way this happens is on the nursing side, decreasing the amount of suction on the blood when taking it out the vein (aka not putting it directly into the vacutainer tubes).