A complete blood count - CBC - consists of about a dozen different tests. They include:

WBC - a count of the number of white blood cells in either a microliter or liter of blood (different countries->different volumes). The difference between them is found in the description. For example, a 4.0x10^3/microliter is the same as 4.0x10^9/liter.

Traditional differential - consists of counting 100 cells and reporting those number as a percentage so LY - percentage of lymphocytes (typically somewhere between 20-40) MO - percentage of monocytes (typically less than 10) GR - percentage of granulocytes (typically between 45 -75) EO - percentage of eosinophils (typically less than 3) BA - percentage of basophils (typically less than 2) So it is possible to have a perfectly acceptable percentage differential using just granulocytes and lymphocytes.

Absolute differential - consists of actually quantifying the real number of a specific cell line in either a microliter or liter. You can do this yourself by simply multiplying the total WBC value by the percentage of the cell line in question.

LY# (sometimes seen as ABS LY) - absolute number of lymphocytes MO# (sometimes seen as ABS MO) - absolute number of monocytes GR# (sometimes seen as ABS GR) - absolute number of granulocytes EO# (sometimes seen as ABS EO) - absolute number of eosinophils BA# (sometimes seen as ABS BA) - absolute number of basophils

Why is this important? Because sometimes the percentage will give you a false impression. For example I said that a 60% gr and 40% ly could be totally acceptable. BUT if the WBC is 2.0 (low), then the absolute counts will tell you that the lymphocytes are actually decreased. if the WBC is 12.0 (high), the the absolute count will tell you that the granulocytes are actually increased.

The next three have reference ranges which will vary by age, gender, physical fitness, or altitude. RBC -a count of the number of red blood cells in either a microliter or liter of blood. So the result will be either 4.50x10^6/microliter or 4.50x10^12/Liter.

HGB - the weight of the protein, hemoglobin, in either a deciliter or liter of blood. Here the values will look significantly different. For example - 14.0gm/dL is equal to 140 grams/liter! interesting mathematical quirk - if you multiply the RBC by 3, you should come close to the hemoglobin value.

HCT - the percentage of the blood that is made up of red cells. If one were to take a specimen of whole blood and allow the cells to sink (centrifugation), the red cells will collect at the bottom of the tube because they are heavier than the white cells and platelets. That mathematical quirk works here to. If you multiply the hgb by 3, you should get close to the hematocrit value. This is called the "rule of three". Normal red cell populations obey it; abnormal one do not.

The rest of these numbers will not vary by age, gender, physical fitness, or altitude. Notice though that they are not individually accurate but an overall description. They don't work so well if the red cell population is highly varied.

MCV - mean corpuscular or cell volume - a description of the mathematically average size of a red cell. If a dozen apples fill a one liter bowl, how much space does 1 apple fill?

MCH - mean corpuscular or cell hemoglobin - a description of the mathematically average weight of hemogobin in each red cell. If a dozen apples weighs 1 pound, how much does 1 apple weigh?

MCHC - mean corpuscular or cell hemoglobin concentration - a description of the mathematically average volume of the cell which is filled with hemoglobin. Hemoglobin does not do too well in solution. Once you get above 36%, it begins to precipitate but you want the cell to be as fully filled as possible so the MCHC should be in the 30's.

RDW- red cell distribution width - remember the bell curve from class grades? Red cells should all be about the same size. They actually range from 8.0 to 6.9 microns in diameter so the area under the bell curve is rather narrow. If the sizes ranged larger/smaller than that, the RDW will increase as it reflects the range in size of the red cells. An example - ten coins are in your hand. Nine of them are the same denomination and one is not. The range of size difference is small. Now, ten coins are in your hand. Each one is of a different denomination and from different countries so some are round, 6 sided, 8 sided, thicker, thinner, etc. The range here is much greater. It turns out that this piece of data is very sensitive to early changes in red cell production and is very valuable.

PLT - count of the number of platelets in either a microliter or liter of blood (different countries->different volumes). The difference between them is found in the description. For example, a 400x10^3/microliter is the same as 400 x10^9/liter.

MPV - mean platelet volume - the mathematically average size of a platelet. This is based on the same principle as the MCV. It was hoped that this datum would be as valuable as the MCV in helping to clarify platelet disorders. Unfortunately, it has not been and most of the time it is ignored. The instruments still print it out for the few times when it does give information.

Whew!