Where further tests or investigations are required, your doctor may arrange them directly or refer you to a hospital specialist, who will organise the appropriate procedures. Tests and investigations can range from simple blood tests to highly sophisticated imaging tests, such as MRI and radionuclide scanning. The tests you will have depend on the nature of the condition that is suspected. Some of the more common tests and investigations are described below.
These are among the most frequently and easily performed medical tests. The composition of the blood can tell a great deal about the state of someone’s health. Blood cell tests look at the number and composition of red and white blood cells and platelets in the blood. They help doctors in diagnosing diseases of the blood, such as anaemia. Blood cell tests can also show evidence of infection because it causes the white blood cell count to rise. Tests on blood chemistry measure the levels of certain chemicals and minerals in the blood and are particularly used to check the functioning of the kidneys and the liver. Finally, blood lipid tests measure the levels of certain fatty substances (known as lipids) in the blood. High levels of some lipids cause fatty deposits to develop on the lining of the artery walls, a condition known as atherosclerosis.
The substances that are usually checked in a urine analysis include glucose, proteins, some electrolytes and creatinine (a product of protein metabolism). The presence of certain hormones in the urine indicates pregnancy. Testing a urine sample may also reveal blood cells, bacteria or other substances that indicate an underlying problem.
Tissue tests, often called biopsies, involve taking a small sample of tissue from the body for examination under a microscope. Biopsies may be done for a number of reasons, including confirmation of a diagnosis or in order to investigate a suspicious lump or area of tissue. In the case of cervical smears, a few cells from the cervix are removed to be examined for pre-cancerous changes.
A dermatologist or allergist can carry out patch tests on the skin to look for evidence of allergic reactions. In these tests, small, diluted amounts of potential allergens are placed on strips or discs, which are then taped to the skin for 48 hours. When the strips or discs are removed, the skin underneath is examined. Skin that is reddened or inflamed indicates an allergic reaction to the substance. Tested areas that show nore action at first are examined again after a further 48 hours for any delayed reaction.
This type of scanning uses sound waves to produce images. The image is formed by the “echo” of the sound waves as they bounce off different parts of the body. The echoes differ in their wavelength according to the density of the area examined. Ultrasound has become an important diagnostic tool, for example to investigate breast lumps in young women and to look for a cause of abdominal pain, such as gallstones. Ultrasound scanning also plays an important part in antenatal testing. A specialised form of ultrasound scanning, known as echocardiography, may be used to assess heart structure and function.
Computerised tomography (CT) scanning
In this technique, X-rays in conjunction with a computer produce images that build up a cross-sectional view of the body. CT scanning makes it possible to gather detailed information about organs and tissues. CT scans are most often taken of the head and the abdomen.
Magnetic resonance imaging (MRI)
Like CT scanning, MRI provides highly detailed crosssectional images of internal organs and structures. These images are created by a computer using information received from a scanner. Unlike X-rays or CT scanning, MRI does not involve radiation; instead, it uses a magnetic field and radiowaves. MRI may distinguish abnormal soft tissue more clearly than CT scanning, and may be used at a greater range of planes through the body than is possible with CT scanning. MRI is especially useful for imaging the brain and for detecting tumours. It is also valuable for looking at the intervertebral discs and may be used to
investigate low back pain.
In radionuclide scanning a radioactive substance called a radionuclide is introduced into the body (usually by injection) and is taken up by the organ or tissue to be imaged. A counter outside the body detects the radiation that is emitted and this information is in turn transmitted to a computer, which transforms it into images. Radionuclide scans may be used to detect abnormal levels of activity in organs such as the thyroid gland and the kidneys and is useful for detecting tumours and other disorders in these organs. Another type of scanning, known as thallium scanning, may be used to investigate heart function.
This procedure allows doctors to look inside the body. A tube-like instrument is inserted into the body. Endoscopes are very fine fibre-optic instruments that allow doctors to view organs and other structures on a monitor. Depending on the area to be viewed, access may be through a natural opening, such as the mouth or anus. Alternatively, it may be through a small incision, which may be made into a joint or the abdominal cavity. Many endoscopic procedures are performed under a general or local anaesthesic.