Introduction The complete blood count (CBC) is one of the most commonly ordered blood tests. The complete blood count is the calculation of the cellular (formed elements) of blood. These calculations are generally determined by special machines that analyze the different components of blood in less than a minute. A major portion of the complete blood count is the measure of the concentration of white blood cells, red blood cells, and platelets in the blood.
When CBC is ordered CBC may be ordered when a person has any number of signs and symptoms that may be related to disorders that affect blood cells. 1.When an individual has fatigue or weakness 2. infection 3. inflammation 4. bruising, or bleeding 5.a doctor may order a CBC to help diagnose the cause and/or determine its severity.
6.When a person has been diagnosed with a disease known to affect blood cells, a CBC will often be ordered on a regular basis to monitor their condition. Likewise, if someone is receiving treatment for a blood-related disorder, then a CBC may be performed frequently to determine if the treatment is effective. 7. Some therapies, such as chemotherapy, can affect bone marrow production of cells. Some medications can decrease WBCs count overall. A CBC may be ordered on a regular basis to monitor these drug treatments.
Parameters of CBC The complete blood count, or CBC, lists a number of many important values. Typically, it includes the following: 1.White blood cell count (WBC or leukocyte count) 2.WBC differential count 3.Red blood cell count (RBC or erythrocyte count) 4.Hematocrit (Hct) 5.Hemoglobin (Hbg) 6.Mean corpuscular volume (MCV) 7.Mean corpuscular hemoglobin (MCH) 8.Mean corpuscular hemoglobin concentration (MCHC) 9.Red cell distribution width (RDW) 10.Platelet count 11.Mean Platelet Volume (MPV)
White blood cells count (WBCs) Evaluation of white blood cells, the cells that are part of the body's defense system against infections and cancer and also play a role in allergies and inflammation White blood cell (WBC) count is a count of the total number of white blood cells in a person's sample of blood.White blood cell (WBC) count The normal number of WBCs in the blood is 4,500-11,000 white blood cells per microliter (mcL). Neutrophils 40-75% of WBCs. Lymphocytes 20-45% of WBCs. Eosinophils 1-6% of WBCs. Monocytes 2-10% of WBCs. Basophils 0-1% of WBCs.
White Blood Cell Differential May or may not be included as part of the panel of tests. It identifies and counts the number of the various types of white blood cells present. May be done as part of or in follow up to CBC)
Leukopenia Caused by : Bone marrow disorders or damage Autoimmune conditions as rheumatoid arthritis and systemic lupus erthrymatosus (SLE) Severe infections (sepsis) Lymphoma or other cancer that spread to the bone marrow Diseases of immune system (e.g.,HIV)
leukocytosis Caused by : Infection, most commonly bacterial Inflammation Leukemia, Myeloprolifrtive disorders Allergies, asthma Tissue death (trauma, burns, heart attack) Intense exercise or severe stress
Erythrocyte count (RBCs) Evaluation of red blood cells, the cells that transport oxygen throughout the body: Red blood cell (RBC) count is a count of the actual number of red blood cells in a person's sample of blood.Red blood cell (RBC) count Normal RBC range is: Male: 4.7 to 6.1 million cells per microliter (cells/mcL) Female: 4.2 to 5.4 million cells/mcL Hemoglobin measures the amount of the oxygen-carrying protein in the blood.Hemoglobin normal values: g/dL in adult males g/dL in adult, non-pregnant females.
Hematocrit measures the percentage of a person's blood that consists of red blood cells.Hematocrit normal values (Hct): in adult males in adult females.
Decrease blood oxygen carrying components (anemia) Acute or chronic bleeding RBC destruction (e.g., hemolytic anemia, etc.) Nutritional deficiency (e.g., iron deficiency, vitamin B12 or folate deficiency) Bone marrow disorders or damage Chronic inflammatory disease Kidney failure
Dehydration Lung (pulmonary) disease Kidney or other tumor that produces excess erythropoietin Smoking Genetic causes (altered oxygen sensing, abnormality in hemoglobin oxygen release) Polycythemia vera—a rare (malignant) disease Increase blood oxygen carrying components (polycythemia)
Red Blood Cell Indices Red blood cell indices are calculations that provide information on the physical characteristics of the RBCs: Mean corpuscular volume (MCV) is a measurement of the average size of RBCs. Mean corpuscular hemoglobin (MCH) is a calculation of the average amount of oxygen-carrying hemoglobin inside a red blood cell. Mean corpuscular hemoglobin concentration (MCHC) is a calculation of the average percentage of hemoglobin inside a red cell. Red cell distribution width (RDW), which may be included in a CBC, is a calculation of the variation in the size of RBCs.
Mean Corpuscular Volume (MCV) The MCV indicates the average volume of the red blood cells. MCV = = (fl) Normal value for the MCV : 80~97 fl Volume of RBC in femtoliters (fl) / μl of blood RBC / μl of blood Hematocrit * 10 RBC count in millions 1 μl = 10 9 fl
If the MCV is less than 80 fl, the RBCs are are smaller than normal (microcytic); caused by iron deficiency anemia or thalassemia, for example. If the MCV is greater than 97 fl, the RBCs are larger than normal (macrocytic), for example in anemia caused by vitamin B 12 or folate deficiency. If the MCV is within the normal range, the RBCs are normocytic
Mean Corpuscular Hemoglobin Concentration (MCHC) The MCHC is an expression of the average concentration of hemoglobin in the red blood cells. It gives the ratio of the weight of hemoglobin to the volume of the red blood cells. MCHC = = Normal value for the MCHC : 32~36 % Hemoglobin in g/dl Hematocrit /dl * 100 (to convert to %) Hemoglobin * 100 Hematocrit %
An MCHC below 32% indicates hypochromia, that may be when MCV is low which is seen in conditions such as iron deficiency anemia and thalassemia. An MCHC above 36% indicates hyperchromia which is seen in conditions where the hemoglobin is more concentrated inside the red cells, such as autoimmune hemolytic anemia, in burn patients, and hereditary spherocytosis, a rare congenital disorder.and red blood cells with a normal MCHC are termed normochromic. Please note that an MCHC above 38% should not occur.
Mean Corpuscular Hemoglobin (MCH) The MCH indicates the average weight of hemoglobin in the red blood cells. MCH = = Normal value for the MCH : 27~31 pg An MCH lower than 27 pg is found in microcytic anemia and also with normocytic, hypochromic RBCs. An elevated MCH occurs in macrocytic anemia and in some cases of spherocytosis in which hyperchromia may be present. Weight of hemoglobin in 1 μl of blood Number of red blood cells in 1 μl of blood Hemoglobin * 10 Red blood cell count in millions ( pg ) 1 g = pg 1 ml = 10 3 μl
Red cell distribution width (RDW) RDW is an index of the variation of red cell size (volume) in a specimen of blood RDW= Size at 80% tile – size zt 20% tile Size at 80% tile + size zt 20% tile Normal range : 10 ± 1.5 % S.D. of size distribution MEAN size Normal range : 13 ± 1.5 %
Advantages of having RDW : 1. Recognize RBC abnormality from CBC 2. Assist in differential diagnosis 3. Following the course of a disease
An example of Complete Blood Count (CBC)
Low value indicates uniformity in size of RBCs High value Indicates mixed population of small and large RBCs; immature RBCs tend to be larger. For example, in iron deficiency anemia or pernicious anemia, there is high variation (anisocytosis) in RBC size (along with variation in shape – poikilocytosis), causing an increase in the RDW.
Plateletes Platelets, also called "thrombocytes", are blood cells whose function (along with the coagulation factors) is to stop bleeding. Platelets have no nucleus: they are fragments of cytoplasm which are derived from the megakaryocyte of the bone marrow, and then enter the circulation. On a stained blood smear, platelets appear as dark purple spots, about 20% the diameter of red blood cells. The smear is used to examine platelets for size, shape, qualitative number, and clumping. The ratio of platelets to red blood cells in a healthy adult is 1:10 to 1:20.
Low platelet concentration is thrombocytopenia and is due to either decreased production or increased destruction. Elevated platelet concentration is thrombocytosis and is either congenital, reactive (to cytokines), or due to unregulated production: one of the myeloprolerative neoplasms or certain other myeloid neoplasms. A disorder of platelet function is a thrombocytopathy. Platelet concentration is measured either manually using a hemacytometer, or by placing blood in an automated platelet analyzer using electrical impedance, such as a coulter counter. The normal range for platelets in healthy Caucasians is 150,000 to 400,000 per cubic millimeter
Increased Platelete Count Known as thrombocytosis caused by : Cancer (lung, gastrointestinal, breast, ovarian, lymphoma) Rheumatoid arthritis, inflammatory bowel disease, lupus Iron deficiency anemia Hemolytic anemia Myeloproliferative disorder (e.g., essential thrombocythemia)