Preventative Screening Tests


I am frequently asked by patients in my office to order test to “screen” for a certain disorder, condition or cancer.  Unfortunately, often what are good intentions isn’t going to get you the information you are looking for but will be a significant expense.  This is when I try to educate people on what a “screening test” really is and what is an appropriate screening test, what ones do work and how we use them.

A large part of what I do every day is “preventative medicine”.  In other words, if we can do things to actively invoke healthy living to reduce the risk of disease or bad health conditions, then I want to have my patients doing this to help them live as healthy and long as lives as possible.  I would love for every day of every patient’s life to be lived to the fullest without thought of disease or illness!  A big part of this is looking for potential illness or risk before it becomes a problem and addressing it early on.  By doing this we hope to prevent death, disability, disease, discomfort and dissatisfaction in/with their life (the 5 Ds).  From a community perspective, practicing preventative medicine reduces the cost to society from loss of productivity, work days or school days, and the cost of healthcare consumption from disease management.

Therefore, I try to at least once a year (if not more frequently) review with each patient their risk factors and screening tests that are appropriate for their age range, risk profile and current health status.  This then prompts appropriate recommendations on what behavioral or lifestyle changes should they be doing or making or changing and what screening tests they should be having done.  It also includes recommendations on immunizations and chemoprevention (specific drugs used to lower their health risks such as a daily aspirin).

First, it would be good to understand what really is a “screening test”.  A“screening test” must be able to detect the disease (illness) we are looking for while ruling the disease process out if it does not exist AND must be able to do this early enough in the course of the disease process to be able to make a significant difference in the outcome of the disease process.  A screening test ideally should also be minimally invasive (it doesn’t benefit to cause harm or torture the entire population in the process!) and it should not cost prohibitive to be able to apply to the population at large.  It ideally should also be screening for conditions that occur at a fairly high rate in the general population to make it reasonable to screen for.

The medical terms used are “sensitivity” and “specificity”.  Sensitivity means there is a high probability of detecting the disease if it is present by the testing process (a true positive rate).  Specificity means there is a high probability of ruling out the disease if it is not present by the testing process (a true negative rate).  The higher the sensitivity, the less likely a false positive test.  The higher the specificity, the lower a false negative test.

If I use a pregnancy test, I want it to have a high sensitivity and specificity.  In other words, I want the test to be a true positive test if the patient is truly pregnant but I want it to tell me the test if negative if the patient is truly not pregnant.  If the sensitivity were only 50%, I have the same odds as flipping a coin or guessing if a patient is pregnant or not when they think they are.  I can also have tests that have high sensitivity (tells me if the condition is present when it is) but a low sensitivity (won’t tell me for sure the test is negative if the disease is not present) or tests with low sensitivity but high specificity (it won’t tell me if the condition is present but it will for sure tell me if it isn’t).  Obviously, the best tests have both high sensitivity and specificity.

The best screening tests are cheap, easy to do and detect disease risk or presence very early on in the disease process or at the first presentation of risk AND it is a condition that I can treat to modify the disease outcome.  One example would be a pap smear test to look for cervical cancer (cancer of the women’s reproductive organ, part of the uterus).  It is fairly non-invasive, reasonably cheap to do, can detect changes very early on and is easy to treat early on that has a great impact on going on to develop full-blown cervical cancer.

There are different levels of prevention as well.  Primary prevention is trying to prevent the 5Ds.  One example would be immunizations. In spite of all of the controversy in our current society, immunizations have significantly reduced illness in our country and the world.  I personally believe it is this exact principle that allows us to have the opinion and luxury of choosing to immunize or not.  If we were living in the era of recurrent infectious disease epidemics, society would have a differing opinion.  Immunizations keep one from getting a disease in the first place by making one immune or building up their immunity against the infectious disease so if they are ever exposed, they don’t become actively infected and get very sick from the infectious disease.

Another form of primary prevention is the rising trend of prophylactic (doing a medical intervention to reduce risk before it happens) mastectomy (removal of the breasts) and oophorectomy (removal of the ovaries) in those women with a very strong family history of genetic breast cancer such as carriers of the BRCA gene.  More simple actions of primary prevention would include recommendations for smoking cessation, seat-belt use and laws against cell phone use and driving.

Secondary prevention is detecting signs of disease process very early on and then going on to diagnose the disease process and treating early on to change the outcome of the disease (see example of the pap smear and cervical cancer above).

Tertiary prevention is used to monitor a disease process that has already been diagnosed to prevent further progression or worsening.  This is part of the treatment process and looks at disease modification over the course of months and years.  One example would be treating high blood pressure to prevent heart attack, stroke, kidney failure, peripheral arterial disease, or congestive heart failure.  Detecting an elevated blood pressure on someone in their 30s isn’t going to make a huge difference in their health status usually at that moment in time but due to the deleterious effects of the disease process over time the damage to the body can be prevented by intervening early on and getting the blood pressure down to goal range and keeping it there.  It is always disheartening when I have someone with a heart attack, stroke or who develops heart failure because I KNOW if we had done a better job starting 20 to 30 years prior in reducing that patient’s risks, we may have prevented that event from ever happening.

There can be a risk to do screening as well.  Such risks include diagnosing inappropriately due to false positives, risk of negative impact of screening (try getting insurance on the open market after being labeled as having a form of cancer), and diagnosing conditions that may not need early and aggressive intervention. Also, when performing screenings, often times other “things” are found that then will lead to further work up and cost that may not have any significant implication in health status but this adds to the overall cost/burden to society under the health care umbrella.  For this reason, recommendations are constantly being reviewed and even changed.  This doesn’t mean that I always agree with the recommendations or rationalization for the change but I will provide you with the recommendations and let you decide.  Ultimately your health and healthcare are up to you.  To download the PDFs associated with the current recommendations for your sex and age, click the link below.  Until next time, Pura Vida!

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