The FBC is used as a broad screening test to check for such disorders as anaemia, infection, and many other diseases. It is actually a panel of tests that examines different parts of the blood and includes the following:
White blood cell (WBC) count is a count of the actual number of white blood cells per volume of blood. Both increases and decreases can be significant.
Red blood cell (RBC) count: is a count of the actual number of red blood cells per volume of blood. Both increases and decreases can point to abnormal conditions.
Haemoglobin measures the amount of oxygen-carrying protein in the blood.
Haematocrit measures the amount of space red blood cells take up in the blood. It is reported as a percentage (0 to 100) or a proportion (0 to 1).
The platelet count is the number of platelets in a given volume of blood. Both increases and decreases can point to bleeding or clotting disorders.
Mean platelet volume (MPV) is a machine-calculated measurement of the average size of your platelets. New platelets are larger, and an increased MPV occurs when increased numbers of platelets are being produced. MPV gives your doctor information about platelet production in your bone marrow.
Mean corpuscular volume (MCV) is a measurement of the average size of your RBCs. The MCV is elevated when your RBCs are larger than normal (macrocytic), for example in anaemia caused by vitamin B12 deficiency or folic acid deficiency. When the MCV is decreased, your RBCs are smaller than normal (microcytic), which may indicate iron deficiency anaemia, inflammation or occasionally thalassaemias.
Mean corpuscular haemoglobin (MCH) is a calculation of the amount of oxygen-carrying haemoglobin inside your RBCs. Since macrocytic RBCs are larger than either normal or microcytic RBCs, they would also tend to have higher MCH values.
Mean corpuscular haemoglobin concentration (MCHC) is a calculation of the concentration of haemoglobin inside the RBCs. Decreased MCHC values (hypochromia) are seen in conditions where the haemoglobin is abnormally diluted inside the red cells, such as in iron deficiency anaemia, long standing inflammation or thalassaemia. Increased MCHC values (hyperchromia) are seen in conditions where the haemoglobin is abnormally concentrated inside the red cells, such as in hereditary or autoimmune spherocytosis.
Red cell distribution width (RDW) is a calculation of the variation in the size of your RBCs. In some anaemias, such as iron deficiency or pernicious anaemia, the amount of variation (anisocytosis) in RBC size (along with variation in shape – poikilocytosis) causes an increase in the RDW.
The FBC is a very common test used to screen for, help diagnose, and to monitor a variety of conditions. Many patients will have baseline FBC tests to help determine their general health status. If they are healthy and they have cell populations that are within normal limits, then they may not require another FBC until their health status changes or until their doctor feels that it is necessary.
If a patient is having symptoms associated with anaemia, such as fatigue or weakness, or has an infection, inflammation, bruising, or bleeding, then the doctor may order a FBC to help diagnose the cause. Significant increases in WBCs may help confirm that an infection is present and suggest the need for further testing to identify its cause. Decreases in the number of RBCs (anaemia) can be further evaluated by changes in size or shape of the RBCs to help determine if the cause might be decreased production, increased loss, or increased destruction of RBCs. A platelet count that is low or extremely high may confirm the cause of excessive bleeding or clotting.
Many conditions will result in increases or decreases in the cell populations. Some of these conditions may require treatment, while others will resolve on their own. Some diseases, such as cancer (and chemotherapy treatment), can affect bone marrow production of cells, increasing the production of one cell at the expense of others or decreasing overall cell production. Some medications can decrease WBC counts, and some vitamin and mineral deficiencies can cause anaemia. The FBC test may be ordered by the doctor on a regular basis to monitor these conditions and drug treatments.
May be increased with infections, inflammation, cancer, leukaemia; decreased with some medications, some autoimmune conditions, some viral or severe infections, bone marrow failure, enlarged spleen, liver disease, alcohol excess and congenital marrow aplasia (marrow doesn't develop normally)
This is a dynamic population that varies somewhat from day to day depending on what is going on in the body.Significant increases in particular types are associated with different temporary/acute and/or chronic conditions.An example of this is the increased number of lymphocytes seen with lymphocytic leukaemia. For more information, see Blood Film and WBC
Increased withB12 and Folate deficiency, liver disease, underactive thyroid, pregnancy, alcohol excess, some bone marrow disorders; decreased with iron deficiency, longstanding inflammatory disorders and thalassaemia
Mean Corpuscular Haemoglobin
May be low in iron deficiency, inflammatory conditions and thalassaemia
Mean Corpuscular Haemoglobin Concentration
Helps with interpretation of MCH
RBC Distribution Width
Increased RDW indicates abnormal variation in RBC size. Can indicate iron deficiency or bone marrow disorders.
Increased numbers of platelets occur with bleeding, inflammation, bone marrow disorders and in patients with absent or underactive spleens. Decreased numbers are associated with immune conditions such as ITP and SLE, vitamin deficiencies, some drugs (especially chemotherapy), alcoholism, liver disease, enlarged spleens, bone marrow disorders and with some rare inherited disorders (such as Wiskott-Aldrich, Bernard-Soulier)
Mean Platelet Volume
Vary with platelet production; younger platelets are larger than older ones
This article was last reviewed on 9 October 2010. | This article was last modified on 9 January 2013.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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