Screening for Disease: What Are the Benefits?

Screening for cancer and chronic diseases may not benefit all patients

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

Screening for cancer and other serious diseases is the norm, but does it always help patients?

A new study found little evidence that screening tools have decreased death rates in some conditions like breast cancer. However, screening may have other benefits, the authors of this study noted. For instance, early treatment can prevent complications in some chronic diseases like diabetes.

Despite the potential benefits of screening, the authors of this study cautioned that doctors and patients should not expect routine screening to always provide major decreases in disease mortality.

Why Screen?

"Screening for detection of diseases such as cancer, heart disease, aneurysms, diabetes or emphysema has been long advocated in an attempt to prevent disease, or to detect it early when treatment is likely to be more effective," said David Winter, MD, MSc, MACP, Chief Clinical Officer, President and Chairman of the Board of HealthTexas Provider Network (HTPN), a division of Baylor Health Care System  This recent article points out that there can be a downside to screenings.

Many diseases start with small changes, and the idea behind screening tools — like mammograms to screen for breast cancer — is to catch the problem early so it can be treated. For instance, if breast cancer is found early, when the cancer is still small, women may need a minor surgery called a lumpectomy. When the tumor is larger, a mastectomy — removal of part or all of the breast — may be necessary.

Early diagnosis may also reduce the cost of treatment for patients.

Screening tools in use today include ultrasounds, CT scans, chest X-rays, blood tests and physical exams.

Because these tests are considered the standard of care, most insurance companies, including Medicare and Medicaid, will pay for them. However, the purpose of the tests — decreasing patient deaths for a specific disease — had not been evaluated before the current study.

What About the Research?

For the current study, a research team led by John P. A. Ioannidis, PhD, of the Stanford School of Medicine in California, set out to review evidence that screening is effective in preventing patient deaths. Their findings were published in the January issue of the International Journal of Epidemiology.

Dr. Ioannidis and team reviewed data from 48 trials and other extensive research reviews. These researchers looked at screening tests for conditions like breast cancer, cervical cancer, colorectal cancer, liver cancer, lung cancer, oral cancer, ovarian cancer, prostate cancer, type 2 diabetes and heart disease.

Dr. Ioannidis and colleagues found evidence of a reduction in patient deaths for specific diseases in only 30 percent of the cases they studied.

These researchers said screening doesn’t stand alone in reducing patient death. If treatment for a disease is not available or not effective, screening cannot save lives, they noted.

In some cases, however, the risk of screening is low but the benefits can be high.

For instance, to screen for high blood pressure, doctors simply check the patient's blood pressure. Several high readings may indicate a problem. If the problem is caught early, people may be able to reduce their blood pressure with diet changes and exercise and not need medications, which may have side effects and can be expensive.

Can Screening Cause Problems?

Screening is not without potential harm. For instance, a false positive result for a disease like cancer can cause emotional distress and physical harm from unnecessary treatment.

"There can be complications from biopsies and procedures, additional testing can induce significant anxiety and radiology studies can induce harm," Dr. Winter told dailyRx News. "Age, individual risks, costs and preferences toward treatment should all be considered. One’s own personal physician is a good source to discuss such issues."

Some screening tests expose patients to radiation or the risk of infection. Chest X-rays and mammograms, for instance, expose patients to small doses of radiation. 

Even when screening doesn’t reduce the death rate, some doctors argue that it has other benefits. For instance, screening for diabetes and high blood pressure can identify people who would benefit from diet or lifestyle changes. Such changes, implemented early, can help prevent or decrease complications like blindness or kidney disease for people with diabetes or strokes in people with high blood pressure.

It’s a Controversial Subject

Dr. Ioannidis and colleagues have provoked a considerable response with their research. Several experts commented on the current study in the January issue of the International Journal of Epidemiology

“Even in the absence of any effect on mortality it is easy for me, as a primary care clinician, to imagine that patients would highly value any screening test and intervention that decreased the risk or severity of these outcomes," wrote Dr. Paul G. Shekelle, of the Southern California Evidence-Based Practice Center in Los Angeles, in an editorial. "So I do not agree with the authors that, for these diseases, any screening test should be assessed with mortality as the main outcome."

Dr. Paul Taylor, of the Institute of Health Informatics at University College London, wrote in an editorial that, regarding disease screening, “The most serious cause of harm is overdiagnosis.”

And Danish medical researcher Dr. Paul C. Gøtzsche, of the Nordic Cochrane Center in Copenhagen, said doctors need to consider the evidence before suggesting screening for healthy patients.

“Screening is popular, but we need to be much more careful in the future when we contemplate approaching healthy people with our screening tests, and should demand much stronger evidence than when we treat patients,” Dr. Gøtzsche wrote in an editorial about the current study.

Take-Home Messages

So what does this mean for the patient? Screening recommendations in the US have not yet changed as a result of the current study. The US Preventive Services Task Force, a national, independent panel of experts, notes that patients and doctors should make decisions about screening together, based on the patient's specific needs.

Review Date: 
January 15, 2015