Blood tests (haematology)

This group of tests includes: liver, kidney and thyroid function tests; diabetes tests and lipid (fats), electrolyte (potassium, sodium, chloride), hormone and drug level tests. Liver Function Tests Liver function can be measured by looking at blood levels of the liver enzymes AST, ALT, ALP and GGT or levels of other substances produced by the liver. High levels of liver enzymes may indicate, among other things: viral hepatitis or other viral infections, the presence of a tumour, alcoholism or diabetes. You may have to fast (not eat or drink) before some of these tests; check with your doctor or the laboratory first. Renal (Kidney) Function Tests Several blood tests will give an indication of how well your kidneys are functioning. These include the serum creatinine test and the urea test. Other renal tests include measurement of potassium and sodium levels and uric acid levels in the blood. High uric acid levels can be a cause of gout (an inflammatory arthritic disease with painful, swollen joints). You may eat and drink normally before having these tests. Thyroid Function Tests The thyroid is a gland at the base of your neck that secretes thyroid hormone (T4), a hormone that affects your body’s metabolism. Common blood tests that measure how well your thyroid gland is working are TSH (thyroid-stimulating hormone) and T4 level tests. You may eat and drink normally before having these tests. Enzyme Tests Creatine Kinase (CK) is an enzyme that can be measured in the blood. Increased levels can be caused by: a lot of exercise, muscle damage and viral infections, but more importantly can indicate that a myocardial infarction (MI or heart attack) has occurred. Troponins are cardiac (heart) enzymes which are higher following a heart attack. You may eat and drink normally before having these tests. Diabetes Tests Diabetes is a disease that affects the way your body deals with sugar. The amount of sugar in your blood is controlled by insulin, a hormone produced by the pancreas (an organ that lies near your stomach). The levels of sugar (glucose) in your blood can be measured either when you have fasted (not eaten) for 12 hours (fasting blood glucose) or after drinking and eating normally (casual or random blood glucose). Blood glucose testing can be used to diagnose diabetes or can be used to measure how well your diabetes is being controlled. The HBA1C (glycated haemoglobin) test measures how well your diabetes has been controlled for the last three months. If you have diabetes, you will probably have this test done once or twice every year. The glucose tolerance test helps a doctor diagnose diabetes if your blood glucose levels are normal but you have some of the symptoms of diabetes. This test is also used to diagnose diabetes during pregnancy (gestational diabetes). The test measures blood glucose levels before and after having a glucose drink. You may have to fast (not eat or drink) before some of these tests; check with your doctor or the laboratory first. Lipid Tests The lipids (fats) measured in blood are cholesterol and triglycerides. Cholesterol can be high-density (HDL cholesterol) or low-density (LDL cholesterol). LDL cholesterol is associated with heart disease, but HDL cholesterol is the opposite and can protect against heart disease. Measuring fat levels in your blood can show if you are at risk of developing heart disease. You may have to fast (not eat or drink) before some of these tests; check with your doctor or the laboratory first. Medicine Level Tests It is possible to measure the levels of some medicines in the blood. Sometimes it is important to do this to make sure that you are not taking too much of a particular medicine. Medicines that may be monitored this way include: digoxin, lithium, theophylline and some anticonvulsants. Alcohol levels in the blood can also be measured. Hormone Tests Measuring levels of the gonadotrophin hormones FSH (follicle-stimulating hormone) and LH (luteinising hormone) in your blood can help diagnose infertility (inability to have children), menstruation (period) problems, early-onset puberty (precocious puberty), premature menopause, or testicular failure. Progesterone is another hormone that may be measured in your blood to see if your ovaries are working properly and can also be used to see if the placenta is working properly during pregnancy. You may eat and drink normally before having these tests. Tumour Marker Tests Measuring blood levels of certain chemicals can indicate the progression of particular diseases. The AFP (alpha-foetoprotein) test can monitor the progress of liver or testicular cancer. The PSA (prostate-specific antigen) test is used in patients with prostate cancer.

Some microorganisms (germs), generally bacteria and yeasts, live in and on the body normally. These organisms can cause disease if they spread to parts of your body where they are not usually found or if your resistance to infection is reduced by stress, injury, use of antibiotics or a viral infection. Other microorganisms, not normally found in or on your body, can also cause disease. When microorganisms cause infectious disease, they are known as pathogens. When a pathogen is in or on your body, samples need to be taken so that the pathogen can be identified and the correct medicine can be used to treat it. Swabs When your doctor, nurse or laboratory technician takes a swab, they gently rub a clean cotton bud over the part of your body they think has an infection. The cotton bud is then wiped onto a special jelly-like material that helps any bacteria present grow. Once bacteria have grown, they can be identified under a microscope. It may take several days for the bacteria to grow. Respiratory (Breathing Tract) swabs may be taken from your throat and from the back of your pharynx (wind pipe) if you have symptoms such as a sore throat or painful sinuses. Skin. If you have a skin infection or have a wound that may be infected, a swab will be taken from the infection/wound site. Ears and Eyes swabs may be taken from your eye or outer ear if you have symptoms of a bacterial infection such as itchy, crusty eyes or a painful ear with discharge. Urogenital swabs may be taken from your cervix, vagina or urethra (women) or urethra (men) if you have symptoms of a genital infection. Urine Infections occur in the bladder, kidney, ureter or urethra and can be identified by examining urine samples. You will be given a container to collect your urine sample in and instructed on how to collect a mid-stream urine (MSU) sample. Faeces (Bowel Motions) If you have symptoms of an intestinal infection, such as diarrhoea, you may be asked for a bowel motion sample so that the pathogen (germ) causing the infection can be identified. You will be given a container and instructions on how to collect the sample. Sometimes you may need to collect two or three samples, taken on different days, to make sure the pathogen is identified correctly and therefore the correct medicine is used to treat the infection. Skin and Nails Scrapings of skin tissue or nail clippings may be taken for examination if you have symptoms of a fungal infection such as ringworm or athlete’s foot. Sputum (Phlegm) A sputum sample may be collected for examination in order to diagnose pneumonia, bronchitis or tuberculosis. Blood Culture If your blood is infected, it can lead to a serious condition known as septicaemia. A blood sample will be taken to identify the pathogen that is present in your blood.

Semen Samples Examination of a semen sample will give a doctor information on how fertile you are or how successful a vasectomy has been. You will be given instructions on how to collect the sample and when it should be taken to the laboratory. Pregnancy Tests Beta Human Chorionic Gonadotrophin (HCG) Test. This is a hormone that is only present during pregnancy. It is the hormone that is tested for when you have a urine pregnancy test. Sometimes blood tests are taken to measure this hormone in your blood. You may eat and drink normally before having this test. Natal Tests Antenatal Blood Tests. Routine blood tests will be performed at your first antenatal doctor visit and during your pregnancy. Amongst other things, these tests will establish your blood type and group. Blood Glucose Tests. Sometimes a type of diabetes called gestational diabetes mellitus (GDM) develops in the second half of pregnancy. If you are 24 -28 weeks pregnant, you will probably be tested for this. You will be given a special drink and a blood sample will be taken one hour later. You may eat and drink normally before having this test. If this test indicates that you might have GDM, you will then have the Glucose Tolerance Test (GTT) to confirm that you have GDM. You will have to fast (not eat or drink) overnight before this test, then you will be given a glucose drink. Blood samples will be taken before you have the drink and one and two hours after. Neonatal Blood Tests Sometimes a sample of blood is collected from the umbilical cord at birth and tested. If your baby has jaundice (yellowing of the skin), blood samples may be taken to measure the levels of bilirubin.

Your immune system is part of your body’s defence system and plays an important role in keeping up your body’s resistance to disease-causing organisms. A healthy immune system can recognise foreign substances (known as antigens) and can develop proteins called antibodies which bind to the antigens and remove them from the body. Some of the cells that produce the antibodies remain as memory cells that can respond quickly and produce antibodies the next time that antigen invades the body. Serologic Tests These tests detect antigens or antibodies in the blood. They can be used to indicate the presence of a particular illness such as hepatitis and certain bacterial and viral diseases, or to measure the level of immunity or resistance your body may have against these illnesses. Autoimmune disorders occur when your body loses its ability to tell the difference between its own tissue and foreign substances. In this case, the immune system attacks some of the body’s own tissues as if they were foreign. Blood samples can be taken to measure antibodies that your body may have produced against specific tissues. Blood tests for autoimmune diseases include Rheumatoid Factor (elevated in rheumatoid arthritis, where the immune system attacks the lining of some of the body’s joints) and Antinuclear Antibody test (elevated in systemic lupus erythematosus). Immunodeficiencies result from defects in the immune system and can either be something you are born with or they can develop when you get an illness. Immune deficiencies very often lead to diseases such as recurrent bacterial infections, viral infections and autoimmune disease. Tests such as the Human Immunodeficiency Virus (HIV), Rubella and Epstein-Barr Virus tests are a measure of how well specific parts of your immune system are working.

Sometimes it is necessary to take a small sample of tissue for examination under a microscope in order to diagnose an illness. Biopsy A biopsy is a portion of a lump, mole or other affected tissue that is removed for examination. Sometimes, the whole lump, mole etc is removed (excision biopsy). Fine Needle Aspiration (FNA) A fine needle is inserted into the affected area and some cells are sucked up for examination.

Examination of tissue samples for cancer cells or cells that may turn into cancer cells is called cytology. The cervical smear test (pap smear) is an example of a cytology test.