Breakspear Medical Pathology Department |
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Haematology & Biochemistry Profile
This blood test is divided into two parts:
- Biochemistry - The measurement of Chemical substances carried by the blood.
- Haematology – The measurement of elements of the blood.
Abnormal results should be interpreted by a doctor in the context of symptoms you may have and with the knowledge of likelihood of any underlying disease. The following description is therefore intended to be a guide only.
Biochemistry Profile
Urea
This is a breakdown product of amino acids, the building blocks of protein. The level can be elevated by a very high protein diet. Conversely, during starvation, protein in the body is broken down and this can also lead to high urea levels. The level is influenced by the state of hydration. A very high level usually indicates impaired kidney function.
Creatinine
This is also a breakdown product in the blood but is not affected by diet. It is a more specific indicator of kidney function.
Uric Acid
This is a waste product of protein digestion. High protein diets and excessive alcohol intake both raise uric acid. A raised level is also caused by a metabolic problem causing the body to manufacture too much uric acid. Too high a level can lead to excess uric acid being deposited as crystals in the tissues of the body, When this occurs in joints, it causes the painful condition gout. More rarely, deposition in the kidneys can cause kidney damage.
Glucose
An elevated blood sugar level may indicate sugar diabetes. Mild elevations may simply relate to very recent high sugar intake, e.g. a Mars Bar. Normally, further tests will be required before a diagnosis of diabetes can be made.
Calcium
This is involved in many metabolic processes, including the normal action of muscles and the heart. Most of our body’s calcium is in our bones. Dietary intake, Vitamin D levels and disease of the bowel, the hormone system and other metabolic disorders can affect the level. Calcium levels in blood samples can sometimes be artificially elevated by the prolonged use of a Tourniquet whilst taking the sample. Excessive use of antacids can also raise the blood level.
Phosphate
Another mineral found abundantly in bone, it is also found in the blood stream and is involved in a variety of metabolic processes.
Bilirubin
This is a breakdown product of haemoglobin, the oxygen carrying protein in the blood. It is removed from the body via the liver, gall bladder and Bowel. Very high levels of Bilirubin in the blood cause the appearance of jaundice (yellowing of the skin). Slight elevations are found in Gilbert’s condition (‘syndrome’). This is a minor enzyme deficiency present in 5% of the normal population. A significantly increased level of Bilirubin can result from gallstones, Liver damage and hepatitis or from certain uncommon blood disorders.
Alkaline Phosphatase(ALP)
This is an enzyme located mainly in the liver and bones. Normal ranges vary greatly during childhood and periods of bone growth. Female values are slightly higher than males. Abnormally high levels can result from liver or bone disease.
Alanine Transferase(ALT)
This is an enzyme produced mainly by the liver. Diseases that affect the liver and the excessive consumption of alcohol may elevate it. Viral illnesses, such as the common cold, can also cause a temporary rise in the ALT level.
Aspartate Transferase (AST)
This is an enzyme created mainly by cells of the liver and the heart. Disease processes or injury affecting either organ may cause release of this enzyme. It is commonly elevated in hepatitis (liver inflammation) associated with viruses or excess alcohol consumption.
Gamma GT (Gamma Glutamyl Transferase)
This enzyme occurs mainly in the liver, kidneys and pancreas. The primary role of cellular gamma glutamyl transferase (GGT) is to metabolise extracelluar reduced glutathione (GSH), allowing for precursor amino acids to be assimilated and re-utilised for intracellular GSH synthesis.
Serum GGT activity has been commonly used as a marker for excessive alcohol consumption or liver diseases. GGT is elevated by prolonged alcohol or drug excess and roughly correlates with alcohol intake. It can be temporarily elevated during generalised viral illness and after excessive paracetamol intake, e.g. self-medication for colds and influenza. Studies consistently suggest that serum GGT within its normal range might be an early and sensitive enzyme related to oxidative stress.
GGT serum measurement provides a very sensitive indicator of the presence or absence of hepatobiliary disease. It is not specific and raised GGT levels have been reported in a variety of clinical conditions including:
- renal failure
- chronic obstructive pulmonary disease
- diabetes
- obesity
- alcoholism
- pancreatic disease
- myocardial infarction
Total Proteins, Albumin and Globulin
These are measurements that can further help assess organ function, immunity and the adequacy of dietary intake.
Haematology Profile
The blood itself has three main particles suspended in a liquid called Serum (plasma).
- Red Blood Cells (or Erythrocytes) – These are responsible for the transport of oxygen and carbon dioxide in the bloodstream and for exchange of these gases in the lungs and body tissues. They contain the specialised protein, haemoglobin, which performs these functions.
- White Blood Cells – These are part of the immune system and fight infection. There are a number of subtypes that are routinely measured (Granulocyte, Lymphocyte and Monocyte).
- Platelets – These are tiny particles that clump together in response to damage to blood vessel walls to prevent bleeding and are part of the blood clotting system.
Individual Measurements
Haemoglobin
Haemoglobin is the substance in our blood carries oxygen. It can be decreased from anaemia or increased by smoking, acclimatisation to high altitude or prolonged physical stress.
Red Cells
This refers to the number of red cells found in a certain volume of blood. Red cells are produced in the bone marrow and normally survive for about three months.
HTC Ratio (PCV)
The haematocrit, or packed cell volume, gives an indication of red cell concentration in a sample of blood. It is usually reduced in anaemia or after a major haemorrhage. It may be increased in smokers.
MCV (Mean Corpuscular Volume)
This is the average size of the red blood cells. They become smaller in iron deficiency, anaemia or larger in Vitamin B12 or Folic Acid deficiency.
Excessive alcohol consumption can also increase red cell size because of its toxic effect on the bone marrow.
MCH (Mean Corpuscular Haemoglobin), MCHC (Mean Corpuscular Haemoglobin Concentration)
These are further measurements that can assist in diagnosis.
White Cells
This is a total count of white blood cells in a certain volume of blood. A profile of the different types of white cells is also shown (Granulocytes, Lymphocytes and Monocytes). The
Granulocyte Count is frequently raised in bacterial infections and the Lymphocyte count may be raised in viral infections.
Platelet Count
The usual explanation for a low platelet count is due to artefact as platelets may clump together in the sample bottle. Occasionally, abnormal platelet counts are caused by disorders of the immune system or bone marrow. The platelet count can also be reduced by a number of drugs.
ESR (Erythrocyte Sedimentation Rate)
This is a very non-specific test of general ‘well-being’. The ESR may be raised in a wide variety of inflammatory diseases and in pregnancy. Mild elevations of the ESR are frequently detected and are usually caused by minor infections, such as the common cold.
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