Blood and pathology tests

Blood and pathology tests make many people uneasy, but they are an important part of detecting, diagnosing and treating disease. When you are unwell, many decisions about your care depend on what these tests reveal. Pathology is the study of disease, including its causes and how it develops.

Pathology tests include blood tests as well as tests on urine, stools (feces) and body tissues. A pathologist interprets the results and looks for abnormalities that may point to disease.

Areas of pathology#

Pathology covers several areas of laboratory medicine, including:

• Anatomical pathology – examines disease in body tissue, often tissue surgically removed from living patients. Cytopathology, the study of disease at the level of individual cells, is a subspecialty of anatomical pathology.
• Forensic pathology – used to find the cause of sudden or unexpected death, or where a death is suspected not to be due to natural causes.
• Clinical pathology – the diagnosis of disease using laboratory testing.
• Chemical pathology – looks at the chemicals in blood and other body fluids.
• Hematology – explores blood disorders.
• Medical microbiology – investigates infection caused by bacteria, viruses, fungi and parasites.
• Immunopathology – looks at immune responses to disease.
• Genetic pathology – looks at genetic diseases.
• General pathology – concerned with all aspects of laboratory investigation of disease.

Why blood and pathology tests matter#

As well as detecting and diagnosing disease, blood and pathology tests are important for:

• Preventing disease – some screening tests, such as a cervical screening test or a mammogram, can reduce the risk of certain cancers through early detection.
• Estimating future risk – for example, checking cholesterol levels or the risk of inherited conditions.
• Supporting research into new treatments and the safety of treatments and procedures.

If your doctor or specialist sends you for tests, it is usually because there is some concern about your health, or you are at an age where certain risks become more likely, and a test is an effective way to find out whether there is a problem. Tests may be used to:

• Screen for disease, sometimes picking it up in its early stages before you are aware of any symptoms, or to detect a genetic or inherited disorder.
• Assess your risk of conditions such as diabetes, heart disease or rheumatoid arthritis.
• Pinpoint the cause of an illness and help your doctor make an accurate diagnosis and treatment plan.
• Help your doctor judge your prognosis, the likely course or outcome of a disease.

If you have cancer, tests can help work out the stage the disease has reached. Your doctor may also take a blood sample to determine your blood type before surgery or a transfusion, to check whether an illness is improving, worsening or stable, and to assess medication levels in your blood and the effects of some medications on your organs.

Screening versus investigation#

Some tests are used for screening, while others are used to investigate disease. The difference usually lies in whether or not you have symptoms.

Screening uses simple tests in a healthy population to identify people who have a disease but do not yet have symptoms. Examples include regular bowel cancer screening for adults and regular cervical screening to detect cervical cancer. Some early antenatal tests are also a form of screening for risks to an unborn baby or its mother. Screening is often delivered through organised public health programs. The aim is to pick up disease in its early stages.

Investigation is for an individual who has symptoms or concerns. If your tests are for investigation, it means you or your doctor want to explore a particular problem further rather than screen a general population.

Common blood and pathology tests#

Your doctor will usually interpret test results alongside other information such as your age, lifestyle and sex.

• Full blood count – a common test used to help diagnose a wide range of illnesses, infections and diseases. It gives information about the numbers and development of cells in your blood (red cells, white cells and platelets). Abnormalities may indicate anemia, infection or some blood cancers, such as leukemia.
• Liver function tests – measure enzymes, proteins and other substances produced or processed by the liver. Results suggesting liver damage may point to one of the many diseases or infections that affect the liver, and can be important for early diagnosis and treatment.
• Iron studies – show whether you have too little or too much iron. Iron is essential to normal red blood cell function. Low levels may indicate anemia, with symptoms such as fatigue and lack of energy. Iron overload may increase the risk of serious conditions such as liver disease, heart failure, arthritis or diabetes.
• Thyroid stimulating hormone (TSH) – looks for or monitors thyroid disorders such as hypothyroidism (insufficient thyroid hormone) and hyperthyroidism (excess thyroid hormone), and can also relate to some cancers and autoimmune conditions. TSH tells the thyroid to make hormones essential to many body functions, including breathing, heart rate, body weight, temperature and energy levels.
• Urinalysis – a set of tests on a urine sample that look for a range of conditions, including liver or kidney disease and diabetes, as well as outcomes such as pregnancy. Urinary tract infections may also be detected with this test or with a rapid urine test.
• INR (International Normalized Ratio) – measures how well the blood clots and is used to monitor the effect of anti-clotting medication. It is an especially important regular test for people taking warfarin, which is used to help prevent stroke or clotting after surgery.

What to expect during the tests#

Blood test#

Having a blood test is usually a simple, standard procedure:

• You attend your appointment and may be asked to sit or lie down for the collection.
• The person collecting your blood (a phlebotomist, but it may be a nurse or other healthcare professional) places a tourniquet around your upper arm and tightens it to increase the blood volume in your veins. You may be asked to clench and unclench your fist a few times.
• The collection site is wiped clean to reduce the risk of infection, then a needle is inserted into your vein and the blood flows into a syringe or vial.
• You may feel a little discomfort. Tell the person collecting your blood if you have any concerns or feel unwell.
• Afterwards you press a cotton wool ball against the site for a few moments, and a small adhesive dressing is applied. Minor bruising at the site is common.

Urine sample#

You may be asked to collect a sample at your doctor’s office or at home, using a small collection bottle. Often a “midstream” sample is requested, which is the urine passed about midway through urination rather than the first or last part. Wash your hands thoroughly after collecting your sample.

At the office, your doctor may do a rapid urine test by placing a test strip into the sample to quickly check for pregnancy or a cause of acute symptoms such as pain. If you collect samples at home, you may need to package the bottles and deliver or mail them to a laboratory.

Stool sample#

Stool samples are usually collected at home. You may be given a kit with gloves and a small container:

• It is usually best to urinate before taking the sample so that urine does not mix with the feces. Be careful not to collect toilet water with the sample.
• Collect the feces into a clean container, or place some newspaper or plastic over the toilet bowl to catch it, then use the small spoon or scoop from the kit to transfer a sample into the container, usually about a third full. Do not let the sample touch the inside of the toilet bowl.
• Screw the lid onto the container. If instructed, write your name, date of birth and the collection date on it.
• Follow the instructions for handing in the sample. Discard the items you used and wash your hands thoroughly.

Where the tests are done#

Your doctor or healthcare professional will tell you where to go for your test. Pathology tests are usually carried out at an approved or accredited hospital, medical center, collection center or pathology laboratory. Accreditation systems help ensure that laboratories meet recognised quality standards, and you can ask whether a laboratory is accredited.

Key points#

• Pathology means the study of disease and its causes and progression.
• Whether a test is for screening or investigation usually depends on whether or not you have symptoms.
• Some early antenatal tests are a form of screening for risks to an unborn baby or its mother.
• Investigative tests are for an individual who has symptoms or concerns, not for a general population.
• A full blood count is a common test used to help diagnose a wide range of illnesses, infections and diseases.

Where to get help#