Screening tests are often used to check for health problems that even the most careful physical exam can miss. Tests ordered while you are healthy are called screening tests. Some, such as the fecal occult blood (poop) test, are based on age-specific health recommendations. Others are ordered based on what you tell your doctor about your health or health issues in your family. If there is a hint of a problem, it can be found and treated before you feel sick.

Screening tests can be a bit inconvenient in terms of time, since results are often normal. However, they are very useful in helping diagnose problems that would otherwise be missed. These tests are one of the most important parts of your annual check-up – an early warning system to help alert your doctor.

Blood tests

Blood supplies all cells in your body with nutrients and oxygen. At the same time, it removes waste products and carbon dioxide. Hundreds of different tests can be done on blood.

Normally, an annual blood test only screens you for the following common health problems.

CBC (Complete Blood Count) – Computers analyze and count each different part of your blood, including red blood cells, white blood cells and the platelets (that help with blood clotting). A CBC can find conditions such as anemia, leukemia, or blood clotting problems.
ALT (Alanine Aminotransferase) – ALT is one of many enzymes made by your liver. Elevated levels of any of the liver enzymes in your blood can signal a liver disease like hepatitis or gall bladder disease.
Serum Creatinine – Creatinine is a waste material produced by active muscles. Your kidneys clear it from the blood into urine. An abnormally high serum creatinine level means that your kidneys are unable to remove creatinine from your body, as in kidney failure.
Lipids – Lipid tests measure levels of triglycerides, bad LDL cholesterol, and good HDL cholesterol. High levels of triglycerides and LDL cholesterol, and low levels of HDL cholesterol, are associated with heart attack and stroke.
TSH (Thyroid Stimulating Hormone) – TSH, a chemical in your body, stimulates your thyroid gland to make thyroid hormone. Abnormal TSH levels warn your doctor that your thyroid is not working properly.
Fasting Glucose – This test measures the amount of glucose in your blood. A high level of glucose in your blood may mean that you have or are at risk of developing diabetes. The Canadian Diabetes Association recommends that everyone over age 40 be screened for diabetes.

Urine studies

Urine, produced by the kidneys, is a mixture of water, electrolytes and other substances. From the kidneys, urine travels down small tubes, called ureters, into the bladder. It is stored there until released from the body via another small tube called the urethra.

Doctors can learn much about how your body is working by analyzing the contents of your urine. Red blood cells show that there has been bleeding somewhere along the urinary or genital systems. White blood cells suggest inflammation, such as a bladder infection. The presence of protein is used to monitor diabetes. As well, doctors are able to find 95 per cent of kidney diseases by measuring a variety of different substances in the urine.

Fecal occult blood

Stool, or feces, is formed mostly from undigested food. It offers important clues about problems somewhere along your digestive system. This includes the esophagus (the tube from the throat to the stomach), stomach, small intestines, large intestines and rectum.

In a fecal occult blood test, stool is chemically analyzed for very small traces of blood. Even if there is so little blood in your feces that you can't see it, this test can still find it.

Blood in the stool suggests that there has been bleeding somewhere along your digestive system. Such bleeding can be caused by many problems including ulcers, inflammatory bowel diseases, and colon cancer. If blood is present, it will not be evenly distributed throughout the stool but deposited in small amounts here and there. For this reason, doctors usually ask that you give three samples for analysis.

Health Canada currently recommends that everyone over the age of 50 be screened for fecal occult blood every two years.

Pap smear

The cervix, or opening into the uterus, is at the end of the vagina (birth canal). Cancer of the cervix kills 8,000 women in North America each year.

The Pap smear, invented by Dr. Papanicolaou, checks the cervix for suspicious cells that indicate cancer. A small swab takes cells from the cervix. These samples are placed on slides and looked at under a microscope.

Pap smears are recommended annually for all women, starting when they become sexually active. Your doctor may choose to do them less often after three negative tests in a row, or after age 65.

Mammograms

A mammogram is used to screen women for breast cancer. Each breast is squeezed between two plates, and low-dose x-rays are used to take a picture. These x-ray pictures help doctors identify changes within the breast that may or may not be cancer. Mammograms can find extremely small lumps that are too tiny to be felt during a physical exam.

If suspicious changes are found in breast tissue, your doctor will order more tests. This might include a breast biopsy, where a sample of the breast is sucked out with a needle. The sample is sent to a pathologist, who checks the tissue to see if changes are malignant (cancerous) or benign (not cancerous).

Current recommendations suggest that mammograms, if started at age 40, should be done yearly. After menopause, a normal mammogram usually means another will not be required for 18 to 24 months.

Bone densitometry

The medical term for a bone scan is Dual Energy X-Ray Absorptiometry, or DEXA. This test uses low-dose x-rays to determine the density of bones. Bones that are less dense are also weaker.

If your bones are weak and more likely to fracture than normal, you have osteoporosis. If your scan detects weak bones, your doctor can help you include exercise and a healthy diet into your lifestyle. A variety of useful medications can build stronger bones.

All men and women over age 65 should have a DEXA bone scan. Those at risk of osteoporosis should have it done earlier. This includes women who have gone through menopause and people with a family history of osteoporosis. Asian and European women with small body frames are also more likely to have weaker bones as they age.

Prostate specific antigen

Prostate Specific Antigen, or PSA, is a substance produced by a man's prostate gland (located just below the bladder). As it is released into the bloodstream, a blood test can measure the concentration of PSA. An elevated level can be normal, but is also associated with prostatitis (inflammation of the prostate gland) or prostate cancer.

Some controversy exists about PSA testing. Some doctors feel it is the best way to screen for prostate cancer before it spreads. Others believe that since PSA often inaccurately predicts prostate cancer, the information it provides is not worth the associated anxiety. In addition, although many men will develop prostate cancer, most die of another disease before the cancer ever becomes fatal.

That being said, the Canadian Cancer Society recommends that all men over age 50 should at least discuss the PSA test with their family doctor. African men and men with a family history of prostate cancer should consider the test even earlier.

Remember, screening tests are not perfect. They may be abnormal even if nothing is wrong. On rare occasions, they can show a normal result when something is wrong. However, if a test result is abnormal, your doctor is alerted to a possible problem and can investigate. If a problem exists, you will receive appropriate treatment as fast as possible and before you feel sick. Your family doctor may also order additional screening tests if you are at risk of specific health problems.

Book a full check-up with your family doctor at least once a year, and faithfully get your screening tests done. This way, you and your doctor can work together to help you live a longer and healthier life.

Screening Tests Helping your doctor protect your health

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