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Health Screening

How do I know that I am healthy?

Many patients ask their doctor to screen them for a variety of diseases such as Cancer, Diabetes and Heart Disease. Their goal is to identify problems early so that they can be treated or cured more easily. Early detection does improve outcome in some conditions, including breast cancer and cervical cancer, but not in others such as lung cancer. Many magazine articles advocate aggressive screening for a variety of conditions despite the lack of supporting evidence for their effectiveness or accuracy. So how do you know what to do? There are 3 basic sources of information: scientific research, expert opinions, and marketeers.
 

Marketeers

Marketeers are the easiest to address since their profit motive is usually obvious. Examples are the "Total Body CT Scan" to screen for "everything", Vascular screening (for Carotid and Femoral artery blockages and Aneurysms), Multiphasic Blood testing (30 blood tests for $30), and CT Scanning for total Coronary Calcium Load (a poor substitute for stress testing and heart catheterization). These are high volume operations that perform a cursory examination or use unproven technology. The tests are performed by a technician and "signed off" by a Physician. They rarely identify significant previously unknown problems, but more often give false positive results that lead to more expensive and invasive testing to prove the patient is really OK. They can also give a patient a false sense of security that they are healthy, and then he or she ignores important symptoms or does not pursue conventional proven screening tests.
 

Expert Opinions

In the absence of good scientific research, sometimes we must rely on expert opinions. But experts are also flawed human beings who have biases. Many experts are passionate about the diseases that they treat and their passion drives their opinions about a particular test or treatment. The American Cancer Society is an excellent organization dedicated to supporting research into cancer treatment and offering resources and support to cancer patients and their families. But their zeal for battling cancer biases some of their cancer screening recommendations (some are not backed up by good scientific research). In other cases there is a profit motive. Recently, there has been a lot of press about the C-reactive Protein (CRP) test as a screen for Coronary Heart Disease. There are many controversies about this test. What is not commonly known is that the use of CRP is being pushed through the media by a physician who holds the patent to the test.
 

Scientific Research

Scientific research is clearly the best source for information. The best studies are Large, Randomized, and Blinded. Large numbers of patients are needed in a study to prove or disprove the effectiveness of a screening test. The patients are usually Randomized, or randomly assigned to a group that is screened or a group that is not screened (or to 2 different screening groups) to eliminate any biases. The groups are then followed over time and their outcomes are compared. In some cases, the researcher does not know which patients are in each group (he is "Blinded") to prevent him from swaying the results. Finally the research must be published in a peer-reviewed journal (the research must be reviewed and approved by experts in the field before it is published). Unfortunately there is a lot of "scientific" research that is not published in a peer-reviewed journal. This research is often poorly done and is full of biases in order to support a product or test.
 

So how can a patient access and understand good research?

Fortunately, for the last decade both patients and physicians have been assisted by the U.S. Preventive Services Task Force (USPSTF). The USPSTF is an independent panel of experts in primary care and prevention that systematically reviews the evidence for clinical preventive services. They analyze scientific research using strict criteria to determine effectiveness for any health screening test. Their reviews and recommendations indexed by health topic can be viewed online: USPSTF Recommendations. Each screening test is evaluated on a Rating Scale.
 

Why are some tests accurate, but still not recommended?

The USPSTF criteria for recommending a test requires not only that a test be accurate, but that it detect disease early enough to make it more curable. So, for example, a CT scan of the chest may be accurate for diagnosing Lung Cancer, but by the time that it shows up on the CT scan, it may already be too late to cure the patient. The USPSTF criteria are as follows:
  • Is there direct evidence that screening reduces death and disease?
  • Is the disease common enough to screen for it? Can a high-risk group be reliably identified?
  • Can the screening test accurately detect the disease?
  • With screening, how much earlier is the disease identified and treated?
  • Does early detection and treatment improve results?
  • Is effective treatment available?
  • Can screening or treatment be harmful?
  • Is the test acceptable to patients?

Please don't hesitate to discuss any of these recommendations with your Provider