Preventing vs. Detecting Disease — What is the Difference?

By Mark A. Kelley, MD |07/11/16

For decades, the public has been educated that prevention is the best way to reduce the risk of disease.

From time to time, news articles describe how some tests or procedures may not be effective in preventing medical conditions. This can be confusing because the reports may not explain the difference between preventing a disease versus detecting it.

Prevention reduces the chance of ever getting a disease. Examples include public measures like clean water; vaccines against smallpox and polio; and lifestyle habits like not smoking. All these significantly reduce the risk of disease.

Detection of disease is a different strategy. If the patient already has the disease or condition, early detection may improve outcome, For example, early detection is particularly important in treating infections. The correct antibiotic, given early, has a much better chance of eliminating the infection before it can spread. In another example, early detection of high blood pressure or high cholesterol can lead to treatment that reduces the risk of heart attacks and stroke.

Some of the recent controversies have been about the early detection of cancer. This is an evolving strategy. Most cancers start as small tumors and cause no symptoms until they grow large or spread. In theory, finding and eliminating these early tumors could result in higher cure rates.

For the most common cancers, this strategy has been effective … but with some uncertainties.

“Early Detection” Success

Cervical Cancer: The Pap smear of the cervix has detected early, curable cancer in thousands of women. Early detection has transformed cervical cancer from an incurable disease to one with a very high cure rate.

Colon cancer: This slow-growing tumor, if detected early, is also highly curable. The detection tools are testing for blood in the stool or looking for tumors inside the colon periodically with a flexible scope.

Skin Cancer: There are multiple forms of skin cancer but in nearly every circumstance, early detection improves cure. The “test” is easy: examination of the skin by a trained expert and when necessary, skin biopsies to determine diagnosis.

“Early Detection” Success – Some Controversy

Breast Cancer: Mammography and related breast imaging technologies are excellent for detecting early breast cancer and this early detection saves lives. However, experts can disagree on the age a woman should begin this testing, or how often it should be performed. These decisions may depend on the woman’s risk for breast cancer based on family history and other factors.

Lung Cancer: Until recently, there was no early detection test for this common tumor. Recent research has suggested that periodic CT scans of the lung can detect early, curable cancer in current or former smokers. However, some experts think this recommendation is preliminary until more results are known.

“Early Detection” – More Controversy

Prostate Cancer: This malignancy grows slowly and is common in elderly men. A blood test called the PSA, when abnormal, suggests prostate cancer but the diagnosis must be confirmed with biopsies. Even if the biopsies confirm the diagnosis, it is often unclear when or how to treat prostate cancer since it is usually not very aggressive. This has made policy-makers wary of recommending the PSA since, so far, the test has not improved the cure rate. However many men and their physicians still monitor PSA levels.

Prevention and detection of disease are important to discuss with your doctor. As medical science gains new insights, some new recommendations may evolve.

However, one recommendation will never change: pay attention to your health and take the steps that can keep you healthy.

For more information about cancer screening tests, visit the website Choosing Wisely.

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