Complete Blood Count (CBC) test is an initial and essential blood test done to evaluate one's overall health and disease state. CBC test is included in routine health check-up, if the doctor is suspecting any disease and for follow up.
CBC test gives us valuable information about Red Blood Cells (RBC), White Blood Cells (WBC) and Platelets circulating in the blood and also gives information about bone marrow activity up to certain extent and helps in making diagnosis and clinical management.
A Medical Personnel collects blood by a simple venipuncture with a small needle prick into the vein, preferably forearm.
CBC test includes wide range of parameters:
1) Red Blood Cell Parameters:
- RBC count:
Assessment of RBCs is to evaluate normal production of red blood cells.
Normal RBC value- Women: 3.5 to 4.5 million/µL, Men: 4.5 to 5.5 million/µL.
The number of red blood cells is determined by age, sex, altitude, exercise, diet, pollution, drug use, tobacco/nicotine use, kidney function, health, and disease status.
Hemoglobin carries oxygen in a red blood cell, helps in diagnosis, treatment and follow up of anemia, a very common condition in India. By measuring the hemoglobin concentration of the blood, the oxygen-carrying capacity of the blood is evaluated.
Normal level of Hb in a healthy adult male is >13gms/dl, in a healthy adult female is >12gms/dl.
Hemoglobin levels below these ranges are termed as Anemia. Hemoglobin is decreased in Blood loss, deficiencies like protein malnutrition, iron, copper, vitamin C, vitamin B1, folic acid, B12, chronic disease, etc.
Hemoglobin is increased in Polycythemia vera, High altitude adaptation, etc.
Hematocrit is the ratio of the volume of RBCs to that of the whole blood and is reported in percentage.
Reference values: Male 38.8–46.4 %, Female: 35.4–44.4 %.
High hematocrit can be seen dehydration, chronic smokers and people living in high altitude etc.
Low levels of hematocrit can be seen in blood loss, anemia, Malnutrition etc.
- RBC indices:
o Mean cell Volume(MCV) is average size of red cells.
Normal range 80-100fL.
Decreased MCV <80FL is Microcytic anemia, seen in iron deficiency, thalassemia, lead poisoning etc.
Increased MCV >100fL, Macrocytic anemia, seen in Vitamin B12, folic acid deficiency, liver disease.
o Mean Corpuscular Hemoglobin(MCH) is the amount of hemoglobin in a single red cell.
Normal range: 24-32pg/cell.
Decrease in MCH- Hypochromasia seen in Iron deficiency anemia.
Increase in MCH is Hyperchromasia, seen in Infants and new born.
o Mean Corpuscular Hemoglobin Concentration(MCHC) indicates average hemoglobin concentration per unit volume (100 mL) of packed red cells.
Normal range: 32–36 g/dL.
Decrease in MCHC is seen in Hypochromic microcytic anemia etc.
Increase in MCHC is seen in Hereditary spherocytosis, Infants and Newborn etc.
• Red cell distribution width (RDW) is a quantitative expression of anisocytosis, i.e, Difference in the sizes of RBCs.Reference values: 11.5–14.5%
Microcytosis, for instance, exists with either iron deficiency or thalassemia. The former condition increases the RDW while the latter does not. Therefore, marked microcytosis with a normal RDW suggests thalassemia early in the work-up.
2) White Blood Cells:
White blood cells are cells of the immune system involved in defending the body against infectious disease and foreign materials. WBCs include Neutrophils, Lymphocytes, Monocytes, Eosinophils and Basophils. These cells play crucial role in maintaining our immune system at check by fighting against all bacterias, viruses, parasites and other micro-organisms.
CBC test gives us Total Leucocyte Count i.e, total number of WBCs per cumm of blood.
Normal range: 4-11 109/L
Increased TLC is >11 109/L is termed Leucocytosis.
Decreased TLC is <4 109/L termed Leucocytopenia.
Increased/Decreased counts can be seen in infection, Inflammation, allergy, patients under chemotherapy, leukemias etc.
CBC test also gives us absolute and differential counts of individual WBCs which gives us clue in suspecting bacterial, viral, parasitic infections, also in chronic long standing diseases and certain type of Blood cancers etc.
Normal circulation of blood in a blood vessel involves the interaction of blood vessel wall, platelets and coagulation factors, they play a significant role in hemorrhage, inflammation which could lead to MI, stroke, and other life-threatening conditions.
Platelet Parameters tested in CBC includes Platelet count and Mean Platelet Volume (MPV).
Normal Platelets in a healthy adult range from 150,000 to 450,000.
Increase in platelet count more than 450,000 is termed Thrombocytosis, associated with Exercise, Parturition, Myeloproliferative Neoplasms, secondary to anemia and infections.
Decrease in platelet count less than 150,000 is termed Thrombocytopenia, seen in conditions associated with bleeding disorders, infections, certain drugs and autoimmune conditions.