Complete blood count : Complete blood count Dr.Kedar Karki Complete blood count : Complete blood count A complete blood count (CBC), also known as full blood count (FBC) or full blood exam (FBE) or blood panel, is a test requested by a doctor or other medical professional that gives information about the cells in a patient's blood. Slide 3: Alexander Vastem is widely regarded as being the first person to use the complete blood count for clinical purposes. Slide 4: The cells that circulate in the bloodstream are generally divided into three types: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets or thrombocytes. Abnormally high or low counts may indicate the presence of many forms of disease, and hence blood counts are amongst the most commonly performed blood tests in medicine, as they can provide an overview of a patient's general health status. Slide 5: Hgb=Hemoglobin, WBC=White blood cells, Plt=Platelets, Hct=Hematocrit. Methods : Methods Samples
A phlebotomist collects the specimen, in this case blood is drawn in a test tube containing an anticoagulant (EDTA, sometimes citrate) to stop it from clotting, and transported to a laboratory.
In the past, counting the cells in a patient's blood was performed manually, by viewing a slide prepared with a sample of the patient's blood under a microscope (a blood film, or peripheral smear). Nowadays, this process is generally automated by use of an automated analyzer, with only specific samples being examined manually. Manual blood count : Manual blood count Counting chambers that hold a specified volume of diluted blood (as there are far too many cells if it is not diluted) are used to calculate the number of red and white cells per litre of blood. Manual blood count : Manual blood count To identify the numbers of different white cells, a blood film is made, and a large number of white cells (at least 100) are counted. This gives the percentage of cells that are of each type. By multiplying the percentage with the total number of white blood cells, the absolute number of each type of white cell can be obtained. Manual blood count : Manual blood count The advantage of manual counting is that blood cells that may be misidentified by an automated counter can be identified visually. It is, however, subject to human error and sampling error because so few cells are counted compared with automated analysis. Automated blood count : Automated blood count The blood is well mixed (though not shaken) and placed on a rack in the analyzer. This instrument has many different components to analyze different elements in the blood. The cell counting component counts the numbers and types of different cells within the blood. The results are printed out or sent to a computer for review. Slide 11: Complete blood count performed by an automated analyser. Differentials missing. Results : Results A complete blood count will normally include:
Total red blood cells - The number of red cells is given as an absolute number per litre.
Hemoglobin - The amount of hemoglobin in the blood, expressed in grams per decilitre. (Low hemoglobin is called anemia.)
Hematocrit or packed cell volume (PCV) - This is the fraction of whole blood volume that consists of red blood cells. Red blood cell indices : Red blood cell indices Mean corpuscular volume (MCV) - the average volume of the red cells, measured in femtolitres. Anemia is classified as microcytic or macrocytic based on whether this value is above or below the expected normal range. Other conditions that can affect MCV include thalassemia and reticulocytosis.
Mean corpuscular hemoglobin (MCH) - the average amount of hemoglobin per red blood cell, in picograms.
Mean corpuscular hemoglobin concentration (MCHC) - the average concentration of hemoglobin in the cells. White cells : White cells Total white blood cells - All the white cell types are given as a percentage and as an absolute number per litre. Slide 15: A complete blood count with differential will also include:
Neutrophil granulocytes - May indicate bacterial infection. May also be raised in acute viral infections.Because of the segmented appearance of the nucleus, neutrophils are sometimes referred to as "segs." The nucleus of less mature neutrophils is not segmented, but has a band or rod-like shape. Less mature neutrophils - those that have recently been released from the bone marrow into the bloodstream - are known as "bands" or "stabs". Stab is a German term for rod. Slide 16: Lymphocytes - Higher with some viral infections such as glandular fever and. Also raised in lymphocytic leukaemia CLL. Can be decreased by HIV infection. In adults, lymphocytes are the second most common WBC type after neutrophils. In young children under age 8, lymphocytes are more common than neutrophils. Slide 17: Monocytes - May be raised in bacterial infection, tuberculosis, malaria, Rocky Mountain spotted fever, monocytic leukemia, chronic ulcerative colitis and regional enteritis
Eosinophil granulocytes - Increased in parasitic infections, asthma, or allergic reaction.
Basophil granulocytes- May be increased in bone marrow related conditions such as leukemia or lymphoma. Slide 18: Platelets
Platelet numbers are given, as well as information about their size and the range of sizes in the blood. Interpretation : Interpretation