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Routine Blood Tests

Often when patients are seen in hospital doctors will undertake a number of blood tests. These tests usually include a full blood count, Urea and electrolytes, liver function tests and a CRP. If further disease specific tests are indicated these will also be included, for example for patients with Coeliac disease undergoing annual review coeliac serology, thyroid function and bone profile (calcium, phosphate and perhaps vitamin D) may also be added.

A full blood count assesses a number of cellular components within the blood including

  1. the number and size of red cells which contain haemoglobin the protein which transports oxygen around the body, a deficiency in these is known as anaemia.

  2. the white cell count; the cells which are responsible for causing inflammation and fighting infection,

  3. the number of platelets, which augment the formation of clots in people with injury or bleeding

Urea and electrolytes

This assesses the level of the key salts sodium and potassium in the blood, as well as giving a measure of how well the kidneys are performing their function.

Liver function tests

This includes the measurement of a number of proteins that are either processed by the liver

  1. bilirubin is a breakdown product of haemoglobin, from red cells and can cause jaundice when it’s level’s rise above normal.

  2. The ALT or AST is a protein made in liver cells and is released from them when they are damaged.

  3. Alkaline phosphatase is a protein made in both liver and bone and can be elevated when either liver, particularly the bile ducts, are damaged.

  4. Albumin is an important protein made in the liver and its levels can fall rapidly either in liver disease or following wider injury or other non -liver diseases.

 

CRP or C reactive protein

This is a protein made in the liver as part of the inflammatory response. The usual level is less than 5 to 10mg/l. Levels can rise to over 500mg/l in severe illness. Levels of CRP often fall and rise relatively quickly with levels rising within 6 hours of an injury or infection. The half life of CRP in the blood is about twenty hours so levels can also fall by 50% or more over 24 hours. This can be a very useful marker in measuring the progress of inflammatory disease and the response to treatment.

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