If we have the power to see our medical future, should we dare look?

What once seemed like science fiction is fast becoming reality. Tests can tell if we have a high risk of prostate cancer, Alzheimer's, Parkinson's disease and various genetic disorders. CT scans can examine every inch of our bodies.

Are all these tests wise for a healthy adult? While mammograms and blood pressure readings have become part of annual checkups for most Americans, the explosion in preventative health exams has triggered a debate over which tests are necessary and which ones simply drive up the cost of health care -- or actually harm a patient.

Some doctors warn that certain screenings may do more harm than good because they expose the body to unnecessary radiation or raise questions that lead to further, invasive probing. Research suggests that some CT scans increase the risk of radiation-induced cancer.

``There are [genetic] tests that could be run on all of us,'' says Dr. Jeffery M. Vance, chairman of the University of Miami's Dr. John T. Macdonald Foundation Department of Medical Genetics. But ``you need to understand why you're doing it. Make sure it's answering the question you want answered.''

CT scans are ``being used for all sorts of diagnostic purposes not envisioned in the past, such as detecting heart disease, [conducting] virtual colonoscopies,'' says Dr. Jeffrey Neitlich, chairman of the Department of Radiology at Mount Sinai Medical Center.

``Patients shouldn't be scared away from CT scans if they need them, but shouldn't have them routinely.''

A study in the August New England Journal of Medicine suggests that as many as 4 million Americans a year are exposed to high doses of radiation from diagnostic scans, with a nuclear heart stress test called the myocardial perfusion scan being the single biggest contributor.

TOTAL-BODY SCANS

Particularly worrisome to Neitlich are full-body scans on healthy people. There has been ``no scientific publication demonstrating that a whole-body CT scan has any impact on life expectancy or quality of life. Therefore, at least at the current time, it's just excess radiation without any proven benefit,'' he says.

While cancer screenings are often life-saving, not all the information is helpful. Among the possible drawbacks, according to the U.S. Preventive Services Task Force:

• Results that falsely indicate cancer, leading to additional tests and worry.

• Failure to find an existing cancer so that the patient ignores symptoms while the disease continues unchecked.

• Detecting slow-growing or non-fatal cancers, leading to treatment that could have been avoided.

PROSTATE CANCER

The American Cancer Society no longer recommends routine PSA blood tests, saying doctors and patients should discuss the implications first.

``Some prostate cancers grow so slowly that they would likely never cause problems. Because of an elevated PSA level, some men may be diagnosed with a prostate cancer that . . . would never have caused any symptoms or lead to their death,'' the ACS writes in its online screening guide.

HEART TESTS

There's disagreement about which tests should be given. Dr. Michael Ozner, director of Wellness and Prevention for Baptist Health South Florida, recommends three blood tests that include the ApoB (``predictive of who's going to have a heart attack'') and the LP(a), which can help detect heart and vascular disease.

But South Beach Diet doctor Arthur Agatston, an associate professor at UM's medical school, recommends the ApoB only ``if the total tri-glycerides are high and the HDL [good cholesterol] is low.'' He also uses advanced blood tests, CT scans and even genetic tests.

Dr. Melissa Tracy, head of UM's cardiac rehab, would try other treatments before ordering the ApoB or the Lp(a).

``For the average person, we don't have evidence-based medicine that treating an elevated ApoB or Lp(a) leads to a positive outcome,'' she says.

Ozner's third recommendation is the high-sensitivity CRP blood test, to tell ``whether arteries are inflamed,'' Studies have shown that people with elevated CRP levels and normal cholesterol were at increased risk of a heart attack, he says.

``In the past we've treated cardiovascular disease like a plumbing problem,'' Ozner says. ``Now we know it's not a cholesterol storage disease, but a chronic inflammation disease. We have three tests that are very important to uncover hidden risks, yet people are bombarded with ads to get 64-slice CT scans.''

Ozner, whose book The Great American Heart Hoax: Lifesaving Advice Your Doctor Should Tell You About Heart Disease Prevention (But Probably Never Will) was published last year, calls the 64-slice heart CT scan for healthy people ``one of the biggest hoaxes perpetuated on the public.

``All that does is gives the patient an inordinate amount of radiation and sends people down the slippery slope to more and more medical intervention,'' he says. ``If you're a man or woman in the ER with the proverbial elephant on your chest, I'm all for CT scans'' and other interventions.

A recent study found the median level of radiation in a heart CT scan is equal to 600 chest X-rays, although the levels varied widely.

``There are a lot of different ways to do cardiac CT scans. You can take two different centers and get twice the radiation at one as at the other,'' says Mount Sinai's Neitlich.

ALZHEIMER'S

As for Alzheimer's disease, many diagnostic tools are in the works. The ApoE gene test is already available.

Vance warns against genetic testing by mail, partly because some of the factors detected by these tests raise alarms when the risk really isn't that high.

``The results are misleading,'' Vance says. ``It's important to have it done with a genetic counselor or a doctor to discuss what it means . . . Other than the very rare mutation, there is no test that's going to tell you 100 percent that you'll get Alzheimer's.''

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