CT scan, CAT scan, pulmonary function, cardiac stress test, treadmill test, PSA, screening, bone density, DEXA scan, Harper Hospital, Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial,

Screening Tests: Part 2

Screening Tests: Part 2

© 2009 Wellness Clubs of America.com

This issue of Health By Design will continue the review of health screening tests. As the available tests are discussed, it is important to keep in mind that a screening test is a test performed upon an individual who appears perfectly healthy, someone who has no signs or symptoms of the disease that the test is intended to uncover.

Most of the tests covered in this series of articles have application as diagnostic tests as well. A diagnostic test is a test done to determine the reason signs or symptoms of disease are present. My comments regarding the use of any particular test to screen apparently healthy individuals do not apply to its use to determine why signs or symptoms of sickness are present.

A test may be of little value as a screening test, but have tremendous value when used as a diagnostic test. Using mammograms to screen asymptomatic women in their twenties and thirties is not recommended because doing so has been shown to increase rather than decrease the number of breast cancer deaths in this age group. Nevertheless, a mammogram is an extremely valuable tool when used to evaluate breast symptoms that are reported by a woman of any age.

An assumption that early detection and treatment of a disease state will always lead to a better outcome than when intervention is delayed is the basis for all health screening. This is almost universally believed to be true. In some instances this assumption has, indeed, proven to be correct. Cancer of the cervix is almost always curable if it is discovered early in its course. Thus, screening for the disease with a pap smear is desirable. Detecting a slight loss of bone strength with a bone density test and addressing the finding appropriately is infinitely superior to waiting until an osteoporotic fracture has occurred.

In other disease states, however, the advantage of detecting a disease before signs or symptoms appear is not so clear cut. The Canadian National Breast Cancer Study strongly suggests that discovery of early, asymptomatic breast cancer may, in fact, result in a worse outcome than had the process been discovered at a later date. The assumption that early detection and treatment of prostate cancer is superior to late intervention has yet to be proven.

Another assumption that underlies the practice of health screening is that highly effective medical treatments are available to reverse a condition that is found to be present. This is not necessarily the case. There are instances in which medical intervention will actually create a more dangerous situation than that found at the time of the screening. It is therefore highly advisable to determine in advance what the response to a positive finding will be.

All too often I see people who have been railroaded into accepting a dangerous treatment because of the findings of a screening test. The damage caused by some treatments is irreversible; had the person known the options in advance he or she would have been prepared to refuse the standard recommendation and pursue a safer course of action. Bone densitometry is an excellent example of this potential trap.

Bone Densitometry

Loss of bone strength is a serious challenge in the United States. More women die each year of hip fractures than die from breast cancer. Osteoporosis, a condition in which bones have become so weak that they are likely to break from minimal stress, is preventable in most instances.

Some of the factors that predispose to the development of osteoporosis are consuming a diet high in animal protein, drinking carbonated beverages, having an inadequate intake of minerals and vitamin D, and hormonal deficiencies. If a bone densitometry screening reveals a loss of bone strength steps should be taken to reverse this condition. These should include dietary measures to diminish the degree of acidity in the body tissues, supplementation of calcium, magnesium, phosphorus, vitamin D, and boron, and providing hormonal support in the form of bioidentical progesterone or DHEA as indicated.

Unfortunately, most individuals who are found to have loss of bone density are told that they much take a bisphosphonate drug. Persons who take these medications shut off their bodies’ ability to renew bone. Bone density increases for the same reason that a branch that has been cut off a tree and allowed to dry out is more dense than a living branch that has remained on the tree. Bones that are not being remodeled in effect “dry out” and become progressively more brittle over time. Eventually the thigh bone will become so brittle that it will snap from bearing body weight. At times the jaw bone will crumble – a condition called “dead jaw” for which there is no effective treatment.

The most accurate screening test for measuring bone density is called a DEXA scan. Not only is the test more accurate than other technologies, those being tested are exposed to lower levels of radiation than some other tests. A DEXA scan typically looks at the density of the spine and hips.

Used in conjunction with sound nutritional measures bone densitometry can be a beneficial screening test. If it is used as an indication to prescribe bisphosphonates it can be dangerous. This is why it is so important to know in advance what the response to an abnormal screening test will be.

PSA Testing

Prostate cancer is the most common form of cancer, other than skin cancer, among men in the United States and is second only to lung cancer as a cause of cancer-related death among men. Current statistics show that 189,000 new cases of prostate cancer will be diagnosed and that approximately 30,200 men will die of the disease each year. It would seem that using a screening test to detect prostate cancer early in its course would be a valuable practice. This is, however, a matter of debate.

In the early 1990s pathologists at Detroit’s Harper Hospital examined the prostate glands of 249 men who had died from various causes. The men were between 20 and 69 years of age at the time of death. The examination results, which were reported in 1994, confirmed that prostate cancer is extremely common. This result was not surprising. It was, however, astonishing to learn just how common prostate cancer is in men of all ages.

Twenty-nine percent of men dying in their thirties had evidence of prostate cancer. This increased to 55 % of men dying in their fifties and to 64 % of those dying in their sixties. The study did not include men aged seventy or beyond at the time of death, but others have shown that the percentage who have prostate cancer continues to increase. It appears that the percentage of men having evidence of prostate cancer is roughly the same as the decade of life being examined.

Despite the fact that approximately one out of three men in their mid-thirties has prostate cancer, we do not see thirty percent of the male population dying of prostate cancer in mid-life. The vast majority of men who have prostate cancer will die of other causes. If they do not undergo PSA screening they will die never having known that prostate cancer was present.

The question that needs to be asked about PSA screening is not whether it is helpful in detecting the presence of prostate cancer. The real question is whether detecting and treating prostate cancer before symptoms develop is more effective in managing the disease than waiting until symptoms appear. This is not an easy question to answer.

It can be argued that prostate cancer is not one, but two disease states. When prostate cancer develops in most men it is a slow-growing, indolent process that is unlikely to ever cause symptoms or lead to death. On the other hand, some prostate cancers are extremely aggressive tumors that will result in premature death if left untreated. Thus a dilemma exists. If early treatment of aggressive prostate tumors is more effective than treatment that is begun once a physical sign, such as the presence of a nodule on the gland appears, PSA screening may be life-saving. If early detection and treatment does not produce significantly better results many men are being unnecessarily subjected to measures that often reduce their quality of life.

Studies conducted to date have failed to show a strong advantage to early treatment of prostate cancer. Two large trials have been conducted, one in the United States and the other in Europe.

The United States study was known as the Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial. Approximately 77,000 men participated; they were divided into two groups of similar size. The first group was offered PSA screening for six years and digital rectal examinations for four years. The second group was not offered either screen, but they were allowed to receive screening from their personal physicians.

The number of men undergoing screening in the first group was 35 percent greater than the number in the second group. As a result, 2,820 men in the “screened” group were found to have prostate cancer as opposed to 2,322 in the “unscreened” group. Despite the higher number of cancers found, there was no difference in death rate after an average of 10 years of follow-up. The study authors concluded that there was no difference in death rate between men who were regularly screened for prostate cancer and those who were not.

The European study was large, involving 162,000 men between the ages of 55 and 69. This study was more successful in separating “screened” from “unscreened” men. The men were randomly divided into two groups with one group receiving PSA screening at four year intervals and the other receiving no PSA screening. The men were followed for 9 years, during which time the number of men found to have prostate cancer was nearly double in the screened group (8.2 % vs. 4.8 %).

A small, but statistically significant, improvement in death rate was seen in the screened group. The difference, however, was quite small – 0.71 deaths per 1000 men. This means that to potentially avoid one prostate cancer death it is necessary for 1,410 men to undergo PSA screening. In addition, 48 of them must accept all of the risks and adverse effects of prostate cancer treatment even though the treatment will not change the outcome of the disease. In other words, the end result for 98% of men found to have prostate cancer by PSA screening will be no different than had they not undergone screening and received early prostate cancer treatment.

What then, is a man to do when PSA screening is offered? If a man is likely to die within ten years due to his age or a known medical condition there is no good reason for having a PSA screen. If a man is likely to survive longer than ten years, PSA screening may be worthwhile if he is willing to change his habits based upon the results.

In the May 2003 issue of Health by Design I presented evidence that PSA levels greater than 1 indicate that the prostate gland is inflamed. Since inflammation is the first phase of cancer development I argued that PSA screening should not be directed toward men over 50, but toward those in their twenties, thirties, and forties. Finding a PSA level greater than 1.0 in a young man would alert him that he was at increased risk of developing prostate cancer. He could then institute changes in diet and begin appropriate nutritional supplementation to lower that risk. I still believe that this is a sensible approach.

Until a reliable means of determining which prostate cancers are likely to become aggressive becomes available, men in their fifties and beyond should carefully weigh the risks of unnecessary prostate cancer treatments against the actual risk of dying from prostate cancer before deciding to accept a PSA screening test.

Electrocardiogram (ECG or EKG)

An electrocardiogram is a recording of the electrical activity of the heart. Its value as a screening test is very limited. Heart rate and rhythm can be determined simply by checking a pulse. It may be helpful to have a “baseline” ECG in one’s forties or fifties to which a later electrocardiogram can be compared if a concern arises, but even this is questionable. There is certainly no reason to include a screening electrocardiogram as part of a routine examination.

Cardiac Stress Test (Treadmill Test)

The recommendation that asymptomatic individuals undergo cardiac stress testing is one of the worst ever made. An ideal screening test would detect the presence of disease 100 % of the time and always be normal in the absence of the disease. No screening test meets this criteria; there are always “false positives” – tests that suggest that a disease is present when it is not – and “false negatives” – results that suggest a disease does not exist when it is actually present.

Treadmill stress tests fail miserably in this regard. It has been reported that a stress test will detect only two out of three instances of advanced narrowing of coronary artery (vessels that supply blood to the heart) narrowing. Likewise, when the test suggests that severe coronary artery narrowing is present it is correct only 70 % of the time. Stating it differently, 1 out of 3 people with severe narrowing of a coronary artery will be told that their coronary arteries are fine while 1 out of every 3 people tested will be told that they have severe arterial narrowing when this is not the case.

It is important to understand that these dismal predictive statistics apply only to advanced coronary artery disease. The ability of a cardiac stress test to predict a future heart attack is actually much less than 67 % of the time. This is because the vast majority of heart attacks occur when a plaque that has only narrowed an artery to 40 or 50 percent of its capacity ruptures, causing a blood clot to form and block blood flow through the artery.

It is difficult to imagine a circumstance under which a stress ECG should be used as a screening test. The odds are far too great that someone at risk of a heart attack will be lulled into a false sense of security and that someone who is not at risk will be required to undergo a coronary catheterization procedure with the risks entailed in doing so. (Because coronary catheterizations are among the most commonly performed surgical procedures in the United States many assume that they do not entail any significant risk. Unfortunately, healthy people occasionally die from complications of the procedure.)

Pulmonary Function Testing

A pulmonary function screening test measures lung volume and the rate at which air can be exhaled from the lungs. This can be quite helpful in identifying individuals who are developing conditions such as emphysema. Smokers and people who work in environments where they are exposed to dust, smoke, or chemicals are the most likely to benefit from screening pulmonary function testing.

CT Scanning

Computerized axial tomography (CAT or CT scanning) is a procedure whereby multiple x-ray images are integrated by a computer to generate a detailed picture of an area of the body. CT scans are quite accurate in identifying tumors, blood clots, and internal injuries. They also reveal calcium deposits within the body.

CT scans are typically done of specific body areas, such as the head, the chest, or the abdomen. Some centers offer a “full body scan” that looks at the heart, lungs, abdomen, pelvis, and bones. While the idea of scanning the body looking for calcium deposits, tumors, gallstones, kidney stones and blood vessel aneurysms may sound attractive, use of any CT scan as a screening test is a questionable practice.

CT scans are x-rays; they entail exposure to radiation. Radiation exposure is cumulative; each incident adds to one’s risk of developing cancer at some point in the future. Two CT scans of an area over the course of one’s lifetime are enough to increase the risk of developing a cancer in that area. When symptoms suggest a disease is present, the benefit of the scan generally outweighs the risk of developing cancer from the procedure. This cannot be said of scans performed to screen for potential problems.

Whole body CT screening scans were popular several years ago, but they have fallen into disfavor for two reasons: The study requires a significant radiation exposure and there is no evidence that whole body scanning detects any diseases early enough to make a difference in their outcome. Nevertheless, it is still being offered by several centers.

Screening scans of the heart are currently promoted heavily, but their value is questionable. While a heart CT is able to detect calcified plaque it is unable to see soft plaque. It is therefore possible to have a normal heart CT scan and still be at significant risk for a heart attack.

CT scanning of the large intestine, called “virtual colonoscopy” is also gaining in popularity. While virtual colonoscopy can detect colon polyps, they cannot be removed at the time of the examination as is often done during an actual colonoscopy. Therefore, a second procedure is generally required if an abnormality is seen. The radiation exposure involved makes repetitive virtual colonoscopies unattractive for screening purposes.

For many years an annual chest x-ray was recommended to screen for lung cancer. Over time it became clear that this had no effect on the outcome of lung cancer and the practice was discontinued. CT scanning of the lungs is now being promoted as screening test for lung cancer, but there is currently no evidence that this will improve lung cancer survival. As with other x-ray procedures, repeat screenings will actually increase the risk of developing cancer.

Health care screening is a lucrative business. As you hear of screening opportunities remember than any medical procedure carries risk as well as potential benefit. Be selective and only pursue tests that have a high probability of providing information helpful to your specific circumstances.

© 2009 Wellness Clubs of America.com

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