by S. Todd Stolp
©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.