Medical Screening Tests - 5 Ways They Can Harm Your Health

Medical screening tests are those performed to identify whether a particular disease or medical condition is present in someone who has no signs or symptoms of the disease in question. Because health screening is offered to healthy people, the criteria for judging the effectiveness of medical screening tests are more stringent than for tests used to diagnose disease in those who have sought medical help for the symptoms of a perceptible illness. The benefits of screening must clearly outweigh potential harm.

Benefits of medical screening tests differ according to the characteristics of the test, and the prevalence (proportion of those with the condition) in the population or sub-population (e.g, sex, age-group, ethnicity) tested. Low prevalence or certain test characteristics lead to more false-positive test results.

Harm From a False-Positive Test Result

A positive test result in someone who does not have the disease will lead to more tests and, if any of these are also positive, possibly to unnecessary treatment. All medical tests and treatments have potential harmful effects, up to and including death. Unnecessary worry or fear from falsely believing one has the disease (cancer, say) may also cause psychological harm. Regular health screening (e.g. annually) with a particular test increases the chance of having a false positive test.

Harm From a False-Negative Result

A negative screening test-result in someone who actually has the disease may lead them to ignore later symptoms and to delay seeking treatment when it is most effective.

Extension of Time With Disease

Medical screening tests should reduce disability or mortality, not just find more cases. If there is no effective treatment for the disease in question, the patient will spend more time being ill than if they had not been tested until symptoms appeared.

Test Itself May Be Harmful to Health

Medical screening tests involving radiation exposure could conceivably increase the risk of cancer over time, especially when used regularly or to screen younger people. Cat-scans deliver the radiation equivalent of about 500 chest X-rays, but are increasingly being offered annually in corporate health screening.

Ineffective Health Screening Reduces Healthcare Resources

The considerable costs and professional time associated with ineffective health screening and its follow-up tests and treatment, reduces the resources available to provide effective healthcare. This may lead to longer waits for specialist care or for treatment, or to some effective interventions not being available to all who need them.

A number of medical screening tests have been shown to be effective in certain populations. For more information on health screening visit the US Preventive Services Task Force http://www.ahrq.gov/CLINIC/uspstfix.htm or http://www.sciencebasedmedicine.org and search for screening.