Wednesday, November 16, 2016
Wisdom Wednesday: The Complete Blood Count (CBC)
This is the most common laboratory test performed – CBC with differential. It is divided into three segments – the red blood cells (RBCs), the white blood cells (WBCs), and the platelets. Today’s blog will concentrate on the RBCs.
The conventional RBC normal range is from 4.6-6.0 million/uL for men and 3.8-5.1 million/uL for women. The functional range for men is 4.2-4.9 and 4.0-4.5 for women. Red blood cells are the most common blood cell making up 25% of all the cells in the human body. They carry 98% of all oxygen to tissues.
Young RBCs are called reticulocytes. Although it takes two days to produce one RBC, your body produces 2.4 million per second.
RBCs have a life span of 120 days and are filtered by the spleen. They are very flexible, flowing easily through the small capillaries and can circulate the body in 20 seconds.
A decrease in the RBC count can be caused by anemia, chronic liver or kidney dysfunction, free radical damage or blood loss. The RBC count increases in dehydration, asthma or respiratory distress, vitamin C deficiency and Polycythemia.
Hemoglobin is the iron carrying portion of the RBC. Four molecules of oxygen can attach to each molecule of hemoglobin. The laboratory range for hemoglobin is 12-16 g/dL but I prefer 14-15 for males and 13.5-14.5 for females. The hemoglobin is decreased in iron deficient anemias, nutritional deficiency, intestinal parasites, internal bleeding, vitamin B6 or copper anemia. It is increased in dehydration, Polycythemia, adrenal dysfunction, asthma, spleen hypofunction and elevated testosterone.
The hematocrit (HCT) measures the percent of RBC’s in the blood. The laboratory range is 36-50% in males and 34-44% in females. I narrow that slightly for the functional range. The hematocrit is a key component of anemia and dehydration screening.
The Mean Corpuscular Volume (MCV) measures the size/volume of a single RBC. This indicates whether the cell is normal, small (microcytic) or enlarged (macrocytic). The laboratory range is from 80-98 u3, but the functional range is 82-89.9 u3. The MCV decreases in iron deficient anemia, blood loss, Rheumatoid arthritis and heavy metal toxicity. It increases in folic acid or B12 anemia, hypochlorhydia (lack of stomach acid), alcoholism, hypothyroidism or liver disease. However, the MCV may be normal if a patient has a deficiency of both iron and folic acid/B12.
The Mean Corpuscular Hemoglobin (MCH) measures the average weight of the hemoglobin in red blood cells. It is used along with the MCV to determine if vitamin B6, B12 or folic acid anemia is present.
The Mean Corpuscular Hemoglobin Concentration (MCHC) measures the average concentration of hemoglobin in RBCs. Again, this is used as an anemia screen because it uses both hematocrit and hemoglobin in its calculation.
The Random Distribution of RBD Weight (RDW) indicates the consistency of the size of RBCs. Reticulocytes (young RBCs) are larger than mature RBCs. So the larger the number, the greater number of reticulocytes present. Increasing reticulocytes is a response by the body to various anemias. The laboratory range is 11.7-15%, but the function norm is below 13%.
The Bottom Line:
That’s probably more information about red blood cells than you ever wanted to know. These tests are very valuable for evaluating various anemias, but they also can yield a lot of additional information. Do yourself a favor and pull out your last CBC and compare your results with the functional norms. Chances are you will find some abnormalities that your physician neglected to mention.
Read Part 2 of The CBC