Complete Blood Count (CBC) Test​ in Hyderabad, India

A CBC is a commonly performed routine blood test which may be ordered to detect or monitor many different health conditions, including:

• If the person is having symptoms, including weakness, fatigue, fever or other signs of an infection, weight loss, bleeding, bruising or any signs of cancer

• When a person is undergoing treatments (such as medications or radiation), that could alter the results of a blood count.

• To monitor a chronic (long-term) health problem that may change the blood count results, such as chronic kidney disease (CKD).

A complete blood count (CBC) test has many uses, including: 

• Diagnosis: A CBC can help identify the cause of symptoms, including weakness, fatigue, fever, pain, bruising, or bleeding. It can also help diagnose conditions including anaemia, leukaemia, infections, and blood cancers.

• Monitoring: A CBC can help monitor conditions that affect blood cell counts, such as anaemia, infection, or blood disorders. It can also help monitor how a person's condition responds to treatment, and may be used to detect side effects of some medical treatments.

• Screening: A doctor may prescribe a CBC as a screening test during routine check-ups to find health problems before there are any symptoms. 

• General health: A CBC can be part of a medical exam to check general health.
  

A complete blood picture (CBP) includes various counts such as red blood cells (RBCs), white blood cells (WBCs), haemoglobin, haematocrit, and platelets. This comprehensive analysis helps assess overall health and detect various medical conditions, including:

Red Blood Cell (RBC) Tests

Red blood cells

RBC stands for red blood cells, are counted in a complete blood picture to measure the amount of red blood cells present per unit volume of patient’s blood and are expressed in cells per microliter (cells/μL). 

Red blood cells are examined in blood counts using parameters such as RBC, haemoglobin (Hb), haematocrit (Hct), Mean Corpuscular Volume (MCV), Red Cell Distribution Width (RDW), Mean Corpuscular Haemoglobin (MCH), and Mean Corpuscular Haemoglobin Concentration (MCHC).

Unlike Hb, RBC does not accurately measure the blood's oxygen-carrying capacity and is not directly used to diagnose anaemia. However, red cell indices are essential in evaluating anaemia.

The RBC count may appear inaccurately low in cases of red cell agglutination or when the sample is diluted due to intravenous fluid infusion.

Haemoglobin

Haemoglobin (Hb) measures the amount of haemoglobin in whole blood and is expressed in grams per decilitre (g/dL). According to the World Health Organization (WHO), normal reference ranges for haemoglobin levels are 13 to 18 g/dL in adult men and 12 to 16 g/dL in adult women who are not pregnant. During pregnancy, the lower limit is generally reduced to 10 g/dL to account for physiological plasma expansion.

A low Hb is called anaemia, while erythrocytosis is defined as a high Hb level. Hb levels are also used to assess the severity of anaemia.

Hb measurement with an automated analyser can be influenced by factors such as plasma volume. For instance, hypervolemic patients may show a haemoglobin level lower than their true level, while severely dehydrated patients may present a falsely high haemoglobin level. 

Similarly, interferents in the specimen, such as lipemia (presence of a high amounts of lipids or fats in the blood), hyperbilirubinemia (build-up of bilirubin in the blood), paraproteinemia (presence of abnormal monoclonal proteins in the blood), or hyperleukocytosis, may falsely elevate the Hb levels. The causes of anaemia are broad and may result from blood loss, destruction of blood cells, or deficient production, or defective production.

Erythrocytosis (excessive red blood cells) can occur due to haemoconcentration or dehydration, or it may result from an increased production of red blood cells. This increased production can be caused by a primary myeloproliferative disorder or may occur secondary to conditions such as cyanotic heart disease, chronic respiratory issues, high altitudes, kidney problems, smoking, or tumours that secrete erythropoietin.

Haematocrit

A haematocrit test measures the percentage volume of red blood cells in the blood calculated with RBC and mean corpuscular volume (MCV): Hct = RBC x MCV/10. 

Normal human blood contains red blood cells, white blood cells, platelets, and the fluid portion called plasma. In this test, the patient red blood cells are separated from the rest of their blood to be measured.

Similarly to Hb, Hct is reduced in anaemia, increased in erythrocytosis, and is influenced by changes in plasma volume.

Red Cell Indices

Red blood cell (RBC) indices are a set of measurements that are calculated as a part of a complete blood count (CBC) test. The indices measure your red blood cells' size, shape, and quality and include:

• Red Cell distribution width (RCDW)
• Mean Corpuscular Volume (MCV)
• Mean Corpuscular Haemoglobin (MCH)
• Mean corpuscular Haemoglobin Concentration (MCHC)

They are calculated using the measured Hb, Hct, and RBC and help clarify the etiology of anaemia. MCH and MCHC are also often used for quality control within laboratories.

• Red cell distribution width: A red cell distribution width (RDW) test measures the degree of variation in red cell size, known as anisocytosis (red blood cells that are of different sizes). The value is calculated as the standard deviation or the coefficient of variation of the MCV distribution curve. RCDW is expressed as a percentage, where a higher value indicates a greater variation in red cell size. RDW is useful in assessing anaemia to help further delineate etiology (underlying cause). The RDW test may also be used with other tests to help detect other conditions, such as thalassemia, an inherited condition that can cause severe anaemia.

• Mean corpuscular volume : Mean corpuscular volume (MCV) measures the average volume and size of the red blood cells present, providing essential information in the diagnostic process for anaemia. MCV is expressed in femtoliters (fL) or cubic micrometers (µm3). To calculate the MCV, the percent haematocrit is divided by the erythrocyte count (RBC count), and the result is multiplied by 10:

MCV (in fL) = (Haematocrit %)/(RBC×1012/L) × 10

Healthcare professionals advise MCV to diagnose anaemia and its type, including microcytic (red blood cells are smaller than normal—low MCV), normocytic (red blood cells are normal in size—normal MCV), or macrocytic (red blood cells are larger than normal—high MCV).

Different etiologies (different causes) are often associated with characteristic red cell morphology. However, assessing anaemia necessitates using RBC indices and peripheral smear examination rather than relying on a single parameter.

Sometimes, MCV may give misleading results (or be spuriously elevated) due to several reasons:

• Red cell agglutination, where doublet erythrocytes are automatically counted as one (Sometimes, red blood cells stick together in clumps (like little groups). When this happens, the counting machines might mistakenly count these clumps as one single cell, making the MCV look higher than it really is)
• Hyperglycaemia occurs when excess glucose causes hypertonic erythrocytes to swell, increasing RBC volume, which can falsely increase the MCV reading.
• Hypernatremia is characterized by too much salt (sodium) in the blood, which causes swelling of hypertonic erythrocytes. For the same reason, hypernatremia can lead to a higher MCV reading.
• Hyperleukocytosis is characterized by a white blood cell (WBC) count greater than 100,000/μL. Some of these larger white cells might be counted as red blood cells when the MCV is calculated, which can also cause the MCV to appear elevated.

Mean Corpuscular Haemoglobin (MCH)

Mean corpuscular haemoglobin (MCH) quantifies the amount of haemoglobin per RBC and is expressed as picograms per red cell (pg/cell). It is not measured directly; the value is calculated by dividing haemoglobin by red cell count. 

MCH (pg) = Hb ÷ RBC count

MCH is dependent on cell volume and correlates closely with MCV. Conversely, the CBC also includes the mean corpuscular haemoglobin concentration (MCHC), which controls for cell volume and is helpful in evaluating anaemia.

Mean corpuscular haemoglobin concentrate (MCHC)

MCHC estimates the average haemoglobin concentration per unit volume of red blood cells, expressed as a gram per decilitre (g/dl) or percentage of Hb per cell.

In contrast to MCH, MCHC correlates the haemoglobin content with the cell volume. Like haemoglobin, the MCHC is reported in g/dL.

The value is calculated by dividing haemoglobin by haematocrit. 

MCHC(g/dL) = haemoglobin ÷ haematocrit

While Mean Corpuscular Haemoglobin (MCH) quantifies the amount of haemoglobin in red blood cells, Mean Corpuscular Haemoglobin Concentration (MCHC) indicates the density of haemoglobin in each red blood cell, taking into account the Mean Corpuscular Volume (MCV). 

The amount of haemoglobin in red blood cells is regulated and is typically limited to an optical density of about 34% haemoglobin per cell.

Increased MCHC can result from abnormalities in red blood cell morphology, such as spherocytosis and xerocytosis, or hemoglobinopathies. 

High MCHC (Mean Corpuscular Haemoglobin Concentration) is often associated with artifacts, which can occur in the following situations:

• Lipemia (presence of excessive amounts of lipid particles in the blood), which spuriously elevates Hb and consequently MCHC
• Haemolysis (breakdown or destruction of red blood cells), where Hb is disproportionally elevated to Hct within the sample
• Red cell agglutination, which spuriously lowers the red cell concentration and elevates MCV
• Leucocytosis (high white blood cell count), which spuriously elevates MCV
• Hyperbilirubinemia (build-up of bilirubin in the blood), which spuriously lowers Hb 
  

White Blood Cell (WBC) Tests

White blood cell count

A white blood count (leukocytes), or absolute WBC count, is part of the immune system and measures the number of white blood cells (WBCs) per blood microliter (μL).

White blood cells (WBCs) are a type of blood cell made in the human bone marrow and found in blood and lymph tissue (part of the immune system). If a person is injured or gets sick, WBCs travel through the bloodstream and tissues to where they are needed. There, they help the body fight off infections and other diseases.

A spurious leukopenia may occur due to white blood cell clumping and may occur in the setting of:

• Cryoproteinemia: an immunologic phenomenon that can cause false elevations in automated white cell and platelet counts
• Reticulocytosis, where nucleated red blood cells are counted as white blood cells
• Fibrin clumps: These are aggregates of fibrin, a protein involved in blood clotting, that form to help stop bleeding by sealing wounds.
• Platelet clumping, where aggregate platelets are counted as white blood cells

Identification of a WBC abnormality involves assessing the white cell differential to identify which white blood cell types are affected, reported either as a percentage of total WBCs or as absolute counts of each type.

The differential may be reported as a percentage of the total WBC or as an absolute count for each mature white cell type.

Neutrophil count 

The neutrophil count, or absolute neutrophil count, is the number of neutrophils per microliter of blood and is expressed as a percentage of the WBC or as an absolute number. Neutrophils are a type of white blood cell that helps the body fight infection.

This count may be used to check for inflammation, leukaemia, infection, and other conditions. 

The lower a person's absolute neutrophil count, the greater the risk of infection. Cancer treatment, including chemotherapy, may reduce the absolute neutrophil count. Also called ANC.

Lymphocyte count 

The lymphocyte count is the number of lymphocytes per microliter of blood and is expressed as a percentage of the WBC or as an absolute number. 

Clinically, the leukocyte count is one of the most economical, convenient, and frequently available markers of inflammation. However, its diagnostic and prognostic importance in cerebrovascular events remains unclear. 

Monocyte count 

The monocyte count is the number of monocytes per microliter of blood and is expressed as a percentage of the WBC or as an absolute number. 

Monocyte cells are a type of white blood cells that fight against certain infections in body and help other white blood cells to destroy cancer cell remove damaged or dead or tissues, and regulate immunity against foreign bodies (substances). 

Monocytes are produced in the bone marrow and subsequently enter the bloodstream, where they make up about 1 to 10% of circulating white blood cells. This equates to approximately 200 to 600 monocytes per microliter of blood, or 0.2 to 0.6 × 109 per litre.

After a few hours in the blood, these cells migrate to tissues including lungs, spleen, bone marrow tissue and liver), where they mature into macrophages.

Eosinophil count 

The eosinophil count is the number of eosinophils per microliter of blood and is expressed as an absolute number or a percentage of the WBC.

Eosinophils (eosinophil cells) are a type of white blood cells (that play an essential role in the body's response to asthma, allergic reactions, and infection with parasites.

Eosinophils typically constitute less than 7% of circulating white blood cells, totalling 100 to 500 eosinophils per microliter of blood [0.1 to 0.5 × 109 per litre]).

These cells play a role in protective immunity against particular parasites and contribute to inflammation associated with allergic disorders. Sometimes, eosinophils cause inflammation in specific organs that results in certain symptoms.

Basophil count 

The basophil count is the number of basophils present per microliter of blood and is expressed as a percentage of the WBC or as an absolute number. 

Basophils (basophil cells) are a type of white blood cell (WBCs) that have a role in wound repair and immune surveillance (such as detecting (identifying early) and destroying very early cancers).

Basophils release histamine and other mediators, initiating allergic reactions.

Basophils comprise less than 3% of circulating white blood cells, ranging from 0 to 300 basophils per microliter of blood [0 to 0.3 × 109 per litre]).

Platelet count 

The platelet count is the number (amount) of platelets per unit volume of blood and is expressed in cells per microliter of blood or cubic millimetre. Platelets, also known as thrombocytes, are small, colourless cell fragments in the blood that help stop bleeding and form clots.

Platelet counts can appear low due to platelet clumping when ethylenediaminetetraacetic acid (EDTA) is present in blood specimen collection tubes, leading to pseudo thrombocytopenia.

When a specimen is collected in a tube containing a different anticoagulant, such as citrate or oxalate, repeating the platelet count is recommended.

The platelet count may be spuriously elevated (falsely elevated) in bacteraemia, fungemia, or malaria, where the analyser counts microorganisms in the blood as platelets. This may also occur in the presence of red blood cell fragments, such as in haemolysis. Other platelet tests include mean platelet volume (MPV), platelet distribution width (PDW), and platelet crit (PCT). However, these are not usually included in the standard Complete Blood Count (CBC) report.