CBC or Complete Blood Count is the most commonly ordered test in routine laboratory practice. CBC reports can be a bit confusing and daunting. So let us try to understand the different parameters in CBC and what do they mean.
Well the report gives a complete picture of the blood sample. It mainly tells us about the different cellular elements of blood i.e., Red Blood cells (RBCs), White Blood cells (WBC’s) and platelets.
Let us discuss them one by one:
Red Blood cells (RBC’s)- They impart the red color to blood. These
cells are anucleate and have biconcave shape. They contain Hemoglobin which carries oxygen to the different cells of our body. So what information about RBC does our report give?
1. RBC Count- the number of RBC’s. It is more in men than women of the same age. The number tends to decrease with age.
2. Hemoglobin(Hb)-This information is quite crucial as it dictates the oxygen-carrying capacity of our blood. It is generally found to be higher in men than in age-matched Females. If it is found to be lower than expected for that age and gender, then the person is said to be suffering from anemia and needs further tests to evaluate and find the exact cause of anemia so that appropriate treatment can be initiated.
3. Hematocrit (Hct)- The volume percentage (vol%) of the RBC’s. It depends on the number and size of the cells. The levels are elevated in conditions that lead to
fall in blood plasma, dehydration, and the more commonly seen dengue fever. For dengue fever, it is advisable to keep the Hct levels under observation as a rise of more than 20% is considered worrisome. Lowered value means low RBC count. Lowered value of Hct along with low MCV and high RDW indicates the possibility of iron deficient anemia. In pregnancy, there is an increase in the fluid volume of blood so there is a physiological drop in Hct.
4. Mean Corpuscular Volume (MCV)- is a measure of the average volume of an RBC. Anemia can lead to its decrease or increase depending on the type of anemia. When the size of the RBCs is reduced, they are called microcytes, when they are increased macrocytes, and when normal normocytes. For example, in iron-deficiency anemia MCV is reduced and RDW is high. In thalassemia, MCV is reduced but RDW is normal. And in megaloblastic anemia caused by a deficiency of Vitamin B12 and folate MCV is increased.
5. Mean Corpuscular Hemoglobin (MCH)-is the average Hb per RBC. It depends on Hb synthesis and the size of the RBC. If they are reduced RBCs are hypochromic. In normal states, they are called normochromic. Reduced MCH is observed in anemia.
6. Mean Corpuscular Hemoglobin concentration (MCHC)- It is the concentration of Hb in a given volume of packed RBC. Low MCHC indicates decreased production of Hb.
7. Red cell distribution width (RDW)- indicates variation in the size and shape of RBCs. In iron deficiency anemia where there is a variation in the size and shape of RBCs, it will be higher. In thalassemia, the Hb is low but there is no variation in the size and shape of the RBCs, so RDW is normal.
White Blood Cells (WBCs)- they are the frontline defenders who protect us from various infections. They are divided into granulocytes and agranulocytes. Granulocytes are Neutrophils, Eosinophils and Basophils.
Agranulocytes are Monocytes and Lymphocytes.
Their increase indicates some infection or an immune reaction. For example, neutrophils are increased in bacterial infections, lymphocytes in viral infections, eosinophils in parasitic infections or allergic conditions like asthma, hay fever, allergic rhinitis etc. Monocytes increase in number in malarial fever. These are just a few common examples- there are numerous other causes for their rise or fall in circulating blood.
Platelets have also gained importance, especially in the rainy and the accompanying fever season. They play a very important role in the clotting of blood. In dengue fever where their number drastically and dangerously reduces, there are chances of bleeding which can be life-threatening. Hence this component of blood is so important. What does CBC tell us about platelets? Their number and average size.
There are few other specialized tests like Immature Platelet fraction (IPF) which measure the immature platelets in the blood. They indicate that new platelet production has started in the bone marrow and the patient is on the path to recovery.
In addition to this, we also study the peripheral blood smear (PBS) for all CBCs. This additional test allows us to confirm the findings of CBC. Also, parasites like filaria and malaria can be demonstrated on PBS. Platelets and WBC can be analysed.
Blood cancer, also called Leukemia can be diagnosed on PBS. In such conditions, the precursor malignant cells enter the peripheral circulating bloodstream and can be demonstrated on PBS before performing any other high end and expensive molecular tests.
Thus, in conclusion, this simple test provides so much information about blood and so it rightly remains one of the most popular and most commonly prescribed tests. Hence, if u wish to know why you are feeling fatigued even after little work, or have flare-ups of asthma, allergic cold, experiencing sudden weight loss, or suffering from fever please go ahead and get your CBC done. This could be your first step towards achieving good health.
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