Pathology

The haemoglobin level is checked and the different blood cells are looked at in detail under the microscope. Various forms of anaemia, bleeding tendencies and infections may be suggested by this test. People on some medications and with longstanding medical conditions may require regular FBCs.

Elevations of serum urea or creatinine may occur with dehydration or if kidney function is impaired. The electrolytes are the various salts in the bloodstream (including sodium, potassium, calcium, chloride and bicarbonate). The potassium level is of particular importance in people on diuretics (fluid tablets) and with impaired kidney function. Calcium levels in the blood may be related to bone health or hormone levels. Abnormal levels of salts are important as markers of disease but may also require treatment in their own right to prevent side effects.

The levels of several liver enzymes rise markedly when the liver is damaged by infections like hepatitis, cancer spread or by toxins like alcohol and certain drugs. Where bile drainage from the liver is blocked, an elevated bilirubin level is seen and jaundice (yellowing of the eyes and skin) results.

It is now clear that a high blood cholesterol level is an important risk factor for heart attacks and stroke. HDL-cholesterol seems to be protective, while LDL-cholesterol appears a major factor in the development of coronary artery disease. Various ratios of HDL, LDL and total cholesterol are also used to predict risk. Recent research has linked coronary artery disease to erectile dysfunction as the conditions may share a common pathway of causation in some cases. It is becoming increasingly clear that hormonal therapy for prostate cancer may alter blood lipid levels and that these should be assessed during treatment.

Hormones are chemical messengers that travel, usually via the bloodstream, to regulate organ function. Blood tests to check the levels of certain hormones may be of relevance in:

• Erectile dysfunction and infertility

• Advanced prostate cancer treatment

• Kidney and adrenal cancers

• Testicular cancer

• Recurrent urinary stones

• Uro-gynaecological cases

Prostate-specific antigen is a substance produced almost exclusively by the prostate which plays a minor role in fertility. The vast majority is released into the ejaculate but tiny amounts are released into the bloodstream and can be detected by a simple blood test. PSA tends to increase with age and age-specific normal values exist. Having a normal PSA does not guarantee that prostate cancer is absent, but makes it less likely.

Abnormally high levels of PSA can be an indication of a disease of the prostate. Common reasons for a high PSA level in the bloodstream may include prostate cancer, benign prostatic hyperplasia (non-cancerous growth), inflammation or infection of the prostate. PSA is used as a screening or case-finding test to help detect prostate cancer.

PSA is a useful tool for diagnosing and monitoring prostate diseases, but further tests are required to confirm which condition is present. Following treatment for prostate cancer, it becomes a useful marker for disease recurrence or progression.

Analysis of the urine includes a series of physical, microscopic, and chemical tests. The tests can screen for kidney disease and infections of the urinary tract. It can also help diagnose diseases that produce waste products called metabolites that are passed from the body in the urine.

Urine cultures help identify organisms that cause an infection that may be present in urine. Urine is placed in a petri dish and incubated in the lab and therefore may require several days to provide a result. Certain infections are very difficult to grow (such as TB), must be cultured in a different way and may take weeks to yield a result.

If an infection is identified, its antibiotic susceptibility is usually tested to determine any medication resistance and allow the correct choice of antibiotic. Urine for culture must be collected in a certain way as a “clean catch” to avoid contamination by organisms that usually exist on the skin. Instructions on how to do this are provided at the lab and it is important to follow them closely.

Urine may also be tested for the presence of cancerous cells. This test is used to screen for cancer of the lining cells of the bladder or ureters (funnels that drain the urine from the kidneys to the bladder). A positive result does not always accurately predict the presence of cancer but does mean that further investigations will be suggested.

This urine test has been developed in New Zealand and is used to screen for bladder cancer. The aim is to decrease the number of flexible cystoscopies that may be required for patients. It is not widely used outside of New Zealand but does have FDA approval for use in the USA. The test involves sending a urine sample away for further testing of genetic material. A number is generated which is used to predict the likelihood that cancer might be present and whether further investigation is indicated.