©September 2008

The United States Preventive Services Task Force is assigned the task of identifying those preventive services which are recommended for the general public.  Several criteria are used to assess various preventive procedures to see if they make sense.  Such criteria include the prevalence of the illness to be prevented, the effectiveness of the detection method, the disability caused by a preventable condition, the effectiveness of disease treatment once it (or the risk of it) is detected, possible negative consequences of a preventive intervention, and finally the cost of a preventive procedure, test or treatment.

First, the public health literature is analyzed to find those health conditions which cause the greatest harm to the population.  Relevant factors include whether a condition is common, whether it leads to considerable disability, and whether it frequently leads to negative consequences or a fatal outcome if not detected.

Secondly, preventive measures to prevent associated illness are assessed to see if they are effective, accessible and safe in preventing the illness.  Immunizations, for instance, are carefully screened before they are licensed to the pharmaceutical companies to determine if they are effective in preventing the various vaccine preventable illnesses, affordable and relatively free of side effects.

Similarly, if effective treatment for the condition is not readily available, then early detection is less likely to demonstrate a benefit.   Small cell carcinoma of the lung continues to have a relatively poor prognosis, even when detected early by a chest X-ray.  This partly explains the reason why routine chest X-rays are not an effective screening test for the general population, although they may be worth considering for certain smokers.

The potential NEGATIVE effects of preventive procedures are also examined by the USPSTF to determine which tests should be recommended.  A chest X-ray does involve exposure to radiation in the form of X-rays, and this is another reason why an X-ray or CT scan is not an ideal screening test.  Also, vaccinations are carefully reviewed for safety before they are widely recommended.  Sometimes new concerns are raised about a particular vaccination after they are widely distributed to millions of people.  The newly identified risk must then be compared again to the effectiveness of the vaccine, but such an assessment should take into consideration the benefits that have already been achieved by a particular vaccine.  It was for this reason that vaccination recommendations changed after polio in the U.S. became so rare that the live oral vaccine was considered less safe than the inactivated injectable vaccine.  Therefore, a switch to the injectable vaccine was recommended.

Some tests have a high false positive rate, meaning that they incorrectly raise the possibility of the presence of an illness when in fact no illness is actually present.  If further investigation for the presence of disease is possibly dangerous, like an abdominal surgery in a patient with an elevated CA-125 blood test for ovarian cancer screening, then this risk must also be considered before suggesting the test in the first place.

Healthy debate about whether or not to participate in screening tests at Health Fairs and through programs that are offered by health systems is part of conscientious personal care.  Unfortunately, there are self-serving programs out there selling screening services for profit rather than for a benevolent interest in improving your health.  To sort through the bewildering array of solicitations that most people receive trying to sell you a preventive service, like bodily CT scans and ultrasounds for otherwise healthy individuals, your personal health care provider is your most valuable resource.  In addition, the USPSTF recommendations are easily accessed with an internet search.

©July 2008

Disease prevention is a familiar battle cry of public health.  It is better to diminish the risk of disease before an assault begins than to wait for the first skirmishes to occur.  But there are several criteria that must be met for a particular test to effectively identify risk of illness, and thereby allow an opportunity to prevent disease.  Colon and rectal (“colorectal”) cancer prevention provides an excellent opportunity to explore the characteristics of screening tests that can make a difference.

The tests recommended for colorectal cancer prevention fall into two categories.  The “fecal tests” involve testing the bowel movements each year by collecting small smears of stool on a card or in a container.  There are several “fecal occult blood tests” (FOBT) available for this which test for the presence of otherwise invisible amounts of blood in the stool.  Each should be done carefully and in accordance with recommendations provided with the test.  There are also new fecal tests available that detect certain cancer markers in the stool, but these are more expensive.

The second category of testing includes examinations of the structure of the lower bowel (the colon) and rectum, most often with a scope called a colonoscope or sigmoidoscope.  Fourteen million annual colonoscopies are performed in this country.

Each person’s health care provider will recommend the test that is most appropriate for the individual based upon factors like family history, age and overall health.  In general and in accordance with American Cancer Society recommendations, colorectal cancer screening should begin at age 50 years.

For a preventive test to be effective, the disease you wish to prevent must be worthy of attention.  It makes little sense to mount a campaign to identify people at risk of developing hiccups.  Colorectal cancer is the second leading cause of cancer death and the third most common cancer in the United States, more than justifying the effort to screen for the disease.

Even though no test is perfect, a test that is used to screen the population for risk of disease must be acceptably accurate, without over-measurement or under-measurement.  In the case of colorectal cancer, the target being measured may be blood in the bowel movement, DNA in the bowel movement or physical abnormalities in the lining of the colon or rectum, called “polyps” (small lumps attached to the lining) or “ulcers” (shallow sores).

Even if the test is accurate, it must be capable of detecting disease risk at a time when steps can be taken to cure the patient.  In some cases, a colorectal cancer test may detect polyps or growths before they are cancerous, and in other cases they may detect growths that have already turned cancerous.  To be effective, a colorectal cancer test must detect cancers or pre-cancers at a time when surgical treatment of the condition, either via a scope or by traditional surgery, is curative.

The test must be affordable.  In an era when “affordable health care” sounds ever more like an oxymoron, there is little need to explain why affordability is a vital part of any health care recommendation.  Screening tests for colorectal cancer may be completely free, such as Fecal Occult Blood Testing at the annual Tuolumne County Health Fair, or screening may run up to as much as $6000 for a colonoscopy and biopsy.  An affordable method of screening should be available for every person, and ultimately saves in health care costs to the community.

Finally, people must be willing to undertake the test.  It is difficult to motivate the public to perform tests on three separate bowel movements when they prefer to deny any personal relationship to sewage whatsoever.  However, people become increasingly compliant with annual stool tests, colonoscopy or other screening modalities as they learn the value of colorectal cancer screening and hear of friends or relatives who have benefited from early detection.

Screening rates for risk of colorectal cancer by low income households in our area steadily decreased between 2001 and 2005, while colorectal cancer screening for the general population increased by almost 10%.  These kinds of trends contribute to the disparity in health between different economic segments of our community.  At least in regards to colorectal cancer prevention, screening tests are available that are effective and affordable.  Please spread the word that this simple test is worth your time: fecal occult blood tests will be available at the Tuolumne County Health Fair in October.

©February 2011

In the 50s, 60s and 70s, the greatest obstacle to the distribution of vaccine to the general population was access to clinical care.  For a large proportion of the U.S. population, understanding the benefits of polio and measles immunization, transportation to a clinic site to receive the vaccine and coverage of the cost of vaccination was beyond reach of the poor.  During that era, much of the adult population had already developed natural immunity to these conditions due to prior infections or earlier vaccination campaigns, so the illnesses tended to specifically target the young.  Therefore, a strategy was implemented to conduct vaccination clinics at schools, since these were sites that were universally attended by children.  The outcome was a public health triumph.  Polio was eliminated from North America and measles, which in 1920 caused 469,924 infections and 7,575 deaths, was declared eradicated from the United States in 2000.  Today, cases and clusters of measles that occur in the U.S. are imported from outside the country.

In 1910, Dr. William Osler expressed his concern for a segment of the population who opposed the use of vaccinations.  At that time, there was a considerable movement against the use of the cow pox vaccine that was being distributed to quell widespread outbreaks of smallpox.  Today, opposition to vaccination continues to be an issue.  While questioning and researching recommendations for maintaining one’s health and the health of one’s family is admirable, an unfortunately large number of unreliable sources of information are now readily available to confuse the picture.  Political turmoil in Pakistan has caused populations to be suspicious that the polio vaccination campaign is a political plot, hobbling efforts to eradicate polio in that country, one of only three in the world in which polio remains endemic.  We should inquire about the risks and benefits of vaccine, but we should be careful not to make decisions about whether to participate based upon personal convictions that may not be based upon good science.

The science tells us that in nearly every case, it is much safer for a person to receive the whooping cough vaccine during infancy and booster vaccines during childhood, also known as “Tdap,” than it is for us to live in a community that remains unvaccinated.  This is well documented by multiple studies conducted by the National Institute of Health, observational studies in the United Kingdom, and confirmed by a study done in British Columbia.  For those extremely rare cases in which a person has experienced a prior untoward reaction to a similar vaccination, your healthcare provider can confirm a medical exemption to assure that such a person does not receive the vaccine.  In such rare cases involving students, the medical provider must sign a Permanent Medical Exemption form to allow the child to attend school.

The need for a Permanent Medical Exemption from any particular vaccine is such a rare condition that communities will easily be able to vaccinate enough of the population to limit the ability of virtually all vaccine preventable diseases from gaining the advantage during an outbreak, as long as those capable of receiving the vaccine do so.  This number – the percent of the population that must be fully vaccinated against a particular infectious disease in order to prevent it from spreading through a community – is different for different diseases.  When this percent of the population is vaccinated, the population is said to have achieved “herd immunity.”  The following is a brief explanation of why achieving herd immunity works.

Imagine that you are a firefighter and it is your job to prevent a community from being burned up in the event that a lightning storm causes a wildfire.  When you look at the record, you notice that one neighboring community has never burned in the forested region around you, and another community has burned to the ground nearly every ten years.  As you look more closely, you learn that the community that has never burned has carefully trimmed underbrush, burned grassland every year to prevent it from growing tall, and has kept a small strip of land clear of trees surrounding the town, thereby preventing wildfires from entering the town and getting out of control by moving from tree to tree and bush to bush.  The community that has frequently burned has not done so.

This is the same strategy used by vaccinating communities to prevent outbreaks of disease.  As long as enough people are vaccinated to prevent the “wildfire” of disease from moving from person to person, the illness will not have enough people who are not immune to the disease to sustain the spread of the epidemic.  How thoroughly a community must trim the thick forest and underbrush to prevent wildfire depends upon the kinds of trees and the local weather, just like different infectious diseases require different levels of immunity in a community in order for the community to achieve herd immunity.