Screening tests look for potential health problems before symptoms appear.

Often, the earlier a disease is diagnosed, the more likely it is that it can be cured or successfully managed. When you treat a disease early, you may be able to prevent or delay problems from the disease. Treating the disease early may also make the disease easier to live with.

Screening tests can cause harm. Harm can come from:

• The test itself.
• An abnormal result that is not correct (a false-positive). This can cause unneeded worry and more tests and treatment that you don't need.
• An abnormal result that may not cause you future harm. This can also cause worry and more tests and treatment that you don't need.
• A normal result that is not correct (a false-negative). This can cause you to take no action. You may ignore symptoms of a problem because you think you are fine.

Commercial screening tests are offered by private companies. The company usually sells a package of tests based on your answers to questions about your age, weight, smoking history, health problems, and other issues. The company may have a doctor you can talk to about the tests. But this is not the same as going to your own doctor who knows your health history.

Commercial bundles often include:

• Electrocardiogram (EKG) or echocardiogram for heart problems.
• Ultrasound tests for problems such as peripheral arterial disease (PAD) and narrowing of the carotid artery.
• Blood tests, X-rays, and CT scans.

You may see offers for these packages in local newspapers or on the Internet. They may be offered at health fairs, places of worship, malls, and fitness centres. A local hospital or group of doctors may sponsor an event where the tests are offered.

No. Not all tests may be right for you. Experts look at research on how well screening tests work. They also look at how a test may help you, whether the test may lead to more tests and treatment, and whether there are any risks or problems with the test. Then they recommend tests based on your age, your gender, your overall health, the cost of testing, and your risk factors. Risk factors are things that make getting a disease more likely. Many screening tests are not needed unless you have risk factors.

There are some important differences between commercial screening tests and tests a doctor may order.

Learning about the disease and the test

When you work with a doctor, the two of you can talk about the test in advance. This may not be possible when you buy a commercial package.

With a doctor, you can ask:

• What the disease is, which test screens for it, and what the test is like. You can learn how the test may help you, whether the test may lead to more tests and treatment, and whether there are any risks or problems the test might cause. You can also talk about how you feel about the test, what you expect from it, and the cost of more testing or treatment.
• How accurate the test is. You can learn how likely it is that the test would miss a disease (false-negative), would show that you have a problem when you don't (false-positive), or would find a disease that will never cause a problem.
• About the treatment. You can learn how much the treatment is likely to help, if it will help you live longer, and whether the treatment itself can cause problems.

Getting your test results

When you work with a doctor, the doctor gets the test results. You will be able to ask questions and talk about the results. You'll be able to ask about next steps. You may be able to take steps to prevent a disease or ask about more testing or treatment.

How you get the results from a commercial package varies. The results may come to you and not to a doctor. A doctor with the company may talk about them with you. You may have to contact a doctor to talk about the results. And you can't be sure that the person who looked at the results was the best person to review them.

If you do talk to a doctor, he or she won't know your health history. This doctor will not be able to order more tests or treat you. You'll need to find your own doctor for that.

With a commercial package, you may not get copies of your medical images, such as X-rays or MRIs, or you may get copies only if they are abnormal. If you don't get copies, you will not have a record of the test. This means you may need to retake the test in the future. And another doctor won't have an earlier image that he or she can compare with images you may get in the future.

Because tests in commercial packages were not ordered by your doctor, the cost of the tests are not covered by provincial health plans. Some private insurance plans may pay for commercial screenings.

Commercial packages often appear to be a good value. You get a lot of screenings for a low price. But you may be paying for tests that you don't need.

Commercial screenings often include tests that most people don't need or that very few people need. For example, experts do not always recommend screening for:

• Carotid artery stenosis (CAS). This ultrasound checks for narrowing of the carotid artery. It is often presented as "screening for stroke." It is not recommended for people who have no symptoms of CAS.^{footnote 1}
• Peripheral arterial disease (PAD). Screening is not recommended for anyone without symptoms of PAD.
• Osteoporosis, if an ultrasound of the heel is used. The most-used screening for osteoporosis is dual-energy X-ray absorptiometry (DXA). All treatment guidelines are based on DXA. Heel tests provide a different form of results that don't give the same information as DXA results. This means there are no treatment guidelines for the results. If a heel test finds low bone density, you may need to have DXA to confirm the results.