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How to read your medical reports: Complete Blood Count

All you need to know about reading your complete blood count test report.

Written by Dr Anitha Anchan |Updated : March 29, 2016 1:04 PM IST

Blood is a specialised fluid that supplies nutrients and oxygen to the various organs, muscles and tissues of the body. It also transports metabolic waste products and carbon dioxide away from them. Blood is made up of blood cells and plasma. There are three types of blood cells - red blood cells (RBCs or erythrocytes), white blood cells (WBCs or leukocytes) and platelets (thrombocytes). Plasma makes up for 55% of blood fluid while the blood cells make up the rest 45%. Plasma contains blood cells, platelets, proteins, glucose, minerals, hormones and carbon dioxide.

Blood tests are a very useful diagnostic tool. There are different kinds of blood tests. During a test, a small amount of blood is taken from your body using a needle and examined under a microscope or tested with chemicals. Increase or decrease in the number or volume of blood components and changes in their shape or size can indicate abnormalities.

Complete blood count what is it?

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A complete blood count (CBC) is one of the most common blood tests. It gives information about the blood cells. The test is used to evaluate your general state of health. It helps detect blood diseases and disorders. Unusually high or low counts may indicate the presence of diseases like anemia, infections, clotting problems, blood cancers, and immune system disorders.

When is the test recommended?

CBC is often done as part of a routine check-up. It is often prescribed when anemia, allergy, infection or bleeding disorder is suspected. It is also recommended before performing surgeries and during cancer therapy to monitor the treatment progress.

Various aspects tested are: RBC count, WBC count, platelet count, hemoglobin, hematocrit or packed cell volume (PCV) and red blood cell indices (MCV, MCH, MCHC and RDW)

Reading your complete blood count

RED BLOOD CELLS (RBC)

They are the most abundant cells in the blood.

1. Red blood cell count tells how many red blood cells (RBCs) you have.

Normal values: Male: 4.7 to 6.1 million cells/cubic mm

Female: 4.2 to 5.4 million cells/cubic mm

Inference: Increased RBC count can be due to:

  • cigarette smoking
  • dehydration
  • congenital heart disease
  • high altitude
  • low oxygen level in the blood
  • medications like gentamicin and methyldopa
  • kidney tumour

Decreased RBC count can be due to:

  • anemia
  • malnutrition (Iron, folate, copper, vitamin B6 and vitamin B12 deficiency)
  • hemorrhage (bleeding)
  • pregnancy
  • leukemia
  • medications like chloramphenicol, quinidine and cancer drugs
  • bone marrow failure
  • erythropoietin deficiency
  • hemolysis
  • multiple myeloma

2. Hemoglobin - RBCs contain hemoglobin, an iron-containing protein, which carries oxygen. Hemoglobin plays a significant role in maintaining the shape of the RBCs.

Normal values: New-borns: 17-22 g/dl

1st week: 15-20 g/dl

1st month: 11-15g/dl

Children: 11-13 g/dl

Adult Male: 14-18 g/dl

Adult Female: 12-16 g/dl

Inference: Decreased hemoglobin leads to anemia which can be due to:

  • loss of blood due to injury or surgery
  • nutritional deficiencies
  • bone marrow diseases
  • cancer drugs
  • kidney failure

Increased hemoglobin levels can be seen in:

  • people living at high altitudes
  • people who smoke
  • dehydration - produces falsely high hemoglobin which disappears on restoration of proper fluid balance
  • advanced lung disease (emphysema)
  • polycythemia rubra vera (bone marrow disorder)
  • abuse of the drug erythropoietin
  • certain tumours

Abnormal hemoglobin is seen in:

3. Hematocrit or PCV is the proportion of whole blood volume that consists of red blood cells.It may be changed by altitude and heavy smoking.

Normal values: Men: 42-52%

Women: 35-45%

Inference: An increased hematocrit level means you're dehydrated. A decreased hematocrit level means you have anemia. Abnormal hematocrit levels also may be a sign of a blood or bone marrow disorder.

4. Mean corpuscular volume (MCV) is the average red blood cell size. Based on the red cell measurement, anemia is classified as microcytic (MCV below normal), normocytic (MCV within normal) and macrocytic (MCV above normal).

Normal value: 80-99 fL (femtolitres)

Inference: Abnormal MCV levels may be a sign of anemia, alcoholism, thalassemia and reticulocytosis.

5. Mean Corpuscular Hemoglobin (MCH) is the average amount of oxygen-carrying hemoglobin inside a red blood cell.

Normal value: 27 to 31picograms/cell

Inference: Decreased in hypochromic anemia

6. Mean Corpuscular Hemoglobin Concentration (MCHC) is the average concentration of hemoglobin inside the red blood cells.

Normal value: 32 to 36 g/dl

Inference: Decreased (hypochromic) in microcytic anemia. Increased (hyperchromic) in hereditary spherocytosis, sickle cell anemia and homozygous hemoglobin C disease.

7. Red Blood Cell Distribution Width (RDW) - The standard size of RBC is about 6 8 m. RDW is the variation in the size of the RBC within a blood sample. Higher values, known as anisocytosis, indicate greater variation in size. It helps in determining the possible causes of the anemia.

Normal reference range: 11-15%

Inference: Increased RDW is seen in pernicious anemia.

WHITE BLOOD CELLS (WBC)

They form part of the body s immune system and help defend the body against infection. Neutrophils, eosinophils, basophils, monocytes and lymphocytes are the various types.

1. WBC count measures the number of white blood cells. Decreased WBCs is called leukopenia. Increased WBCs is called leukocytosis.

Normal range: 4,500-10,000 cells/microliter (mcL)

Inference: Decreased WBCs may be due to

  • bone marrow deficiency
  • disease of the liver or spleen
  • exposure to radiation, etc.

Increased WBCs may be due to

  • anemia
  • infections
  • inflammatory diseases
  • leukemia, bone marrow tumor, etc.

2. A blood differential count measures the number of each of the five types of WBCs in your blood: neutrophils, lymphocytes, monocytes, eosinophils and basophils.

Normal values: Neutrophil 40-75 % of WBCs

Lymphocytes 25-40% of WBCs

Monocytes 2%-8% of WBCs

Eosinophil 0%-7% of WBCs

Basophil 0%-1% of WBCs

Inference: Neutrophil count increased in bacterial and acute viral infections and decreased in aplastic anemia, and recent chemotherapy or radiotherapy. Lymphocyte count increased in viral infections and chronic lymphocytic leukemia (CLL) and decreased by HIV infection. Monocyte count increased in bacterial infection, malaria, tuberculosis, monocytic leukemia, chronic ulcerative colitis, etc. Eosinophil count increased in parasitic infections, asthma or allergic reaction. Basophil count increased in leukemia or lymphoma.

PLATELETS

They are the blood cells that help the blood to clot (thicken)

1. Platelet count measures the number of platelets in your blood. Increased platelet count is called thrombocytosis. Decreased platelet value is termed thrombocytopenia.

Normal values: Adults: 140,000-400,000 cells/cubic mm

Children: 150,000-450,000 cells/cubic mm

Inference: Increased in bleeding, iron deficiency, cancer or diseases of bone marrow and decreased in pregnancy or idiopathic thrombocytopenic purpura (ITP).

2. Mean platelet volume (MPV) is the measurement of the average size of platelets.

Normal value: 7.5 11 fL(femtolitre)

Inference: Increased in immune thrombocytopenic purpura (ITP) and myeloproliferative diseases. Abnormally low MPV values are seen primarily with thrombocytopenia due to impaired production (aplastic anemia).

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