Do medical screenings improve health outcomes?

Question

I've heard that medical screenings are useful, and also that medical screenings don't improve health outcomes.

Do medical screenings improve health outcomes? Are they worth their risks?

Answer 1

This answer is based on (http://www.sciencebasedmedicine.org/a-skeptical-look-at-screening-tests/)

Here are some of the criteria for a good screening test:

• Disease has serious consequences
• Screening population has high prevalence of the condition
• Not too many false positive or false negative results
• Test detects disease before critical point
• Test is safe – causes little morbidity
• Test is affordable and available
• Treatment exists and is not too risky or toxic
• Treatment is more effective when started earlier

Using mammography as an example, "If 1,000 women [from the general population] are screened yearly for 10 years starting at age 50":

• 2-10 will be over-diagnosed and treated unnecessarily
• 5-15 will be diagnosed earlier without any change in the final outcome
• 500 will have at least one false alarm
• 250 will undergo biopsy
• 1 life will be saved
• 999 would have lived just as long if they had never had a mammogram

In the case of PSA testing for prostate cancer,

To prevent one death from prostate cancer, 1,068 men would have to be screened and 48 treated. But here’s the kicker: there was no reduction in all-cause mortality. The overall death rate was the same in the screened group as in the unscreened group.

The recommendations are:

• Don’t screen men under 40 or over 70
• Don’t screen men with a life expectancy of less than 10-15 years
• Don’t screen men age 40-50 who are at average risk
• Consider screening men age 55-69 who are at average risk
• Consider screening high risk men of any age
• Before any screening, doctor should discuss risks and benefits with patient

"The USPSTF is an independent group of experts who keep up with the current medical literature and issue recommendations based on the best available evidence."

They recommend:

• Pap smear (age 21-65, every 3-5 years)
• Colorectal cancer (choice of tests, age 50-75)
• Diabetes (only if blood pressure is elevated)
• Cholesterol (men over 35; women and younger men only if they are at increased risk)
• and others.

They recommend "against doing these tests as routine screening tests because they do more harm than good":

• Annual chest x-ray
• TB tine test
• Scoliosis check
• EKG
• Teaching patients to do breast and testicular self-exams

The above are just samples. Their full set of recommendations are available here. Most screenings have customized recommendations for particular risk groups.

The article concludes:

Screening tests can be very valuable but they can sometimes do more harm than good. They should be chosen judiciously, and the USPSTF offers sound recommendations based on the latest available evidence.