Disease Screening: how much, for what, of which people?

In my last newsletter piece on home water testing for contaminants, I promised to do another on other home health risks. I shall do that in April, but this time I want to respond to a recruitment brochure encouraging me to be screened for $75+ for 5 diseases, by a traveling ultrasound service in a nearby town office. It made me realize the immediacy of issues raised by such programs, their hidden risks, potential benefits, and personal and financial costs. I presume most of you, at least those over 40, receive these solicitations as regularly as I do

Screening for asymptomatic, serious disease, and curing it before it makes one sick, makes good theoretical sense. But while many screening tests are proposed, very few are supported by populations studies showing significant benefit enough to warrant their risks and costs. There are some that clearly do; we are all familiar with Pap smear screening for cervical cancer. As a result of its widespread implementation, cervical cancer rates are 1/5 of those 40-50 years ago.

More recently, screening for colon cancer by colonoscopy has gained acceptance because studies show some benefit, though only in the range of 1/1000 people in whom it’s done regularly. And, unlike Pap smears, there are bowel perforation and bleeding risks in all those 1000 (“number needed to test”). So the decision to screen that many, while helping only one, is more problematic, without even considering the financial costs. Another recent hot screening proposal, annual CT x-ray scanning of the chest for lung cancer in smokers, is being pushed despite much more unfavorable “numbers needed to test”, unknown long term radiation risks, unnecessary chest surgeries for the many who prove to have “false positives” (a change only proven benign after surgery), and no overall benefit in survival for the screened people. Right now, several competing hospital systems in Maine have bought multi-million dollar CT machines to do this, and now have to recruit lots of patients to pay for them. But similar amounts spent on supporting people stopping smoking would be much more efficacious.

Which brings me back to those screening clinics. Some are clearly good and work. The hypertension/cholesterol screening done in Franklin Co., led by Dr. Burgess Record over the past 30+ years, has reached most of that county’s population and effected an almost 50% decline in cardiovascular disease and deaths there, compared to adjacent Somerset and Oxford counties. Such screening for risk factors and altering them with medications and dietary changes (like helping people stop smoking, too) has a much bigger impact than than trying to detect a disease after it appears and eradicating it.

It is the latter, less efficient strategy, which the ultrasound clinics follow when they offer to screen for carotid, leg, and aortic artery disease, osteoporosis, and others. Here there are huge issues with how many must be screened to find one who benefits, huge hidden costs and bother in investigating whether patients with positive tests have significant disease, false reassurance if tests are negative but falsely so, and little or no evidence that eventually offered treatments do any good (see:http://www.sciencebasedmedicine.org/index.php/ultrasound-screening-misleading-the-public/).

All these issues become minor if a person has symptoms, in which case they should be seeing their primary care clinician to pursue them. These clinics are dangerous substitutes for people worried about symptoms.

So the old adage of “if it ain’t broke, don’t fix it” proves true for many, many population screening proposals, with some notable exceptions like cervical cancer, hypertension, mammography over age 50 (though the British don’t think its worth it), maybe osteoporosis if you only use prescription medications with their risks for true osteoporosis not osteopenia, maybe prostate PSAs between age 50-70 if you are willing to accept draconian treatments if it’s found, and on and on.

Be wary also of organizational and professional conflicts of interest, and  cautious about which disease screening is worth it for you. Talk about it with your primary care clinician. Read what the US Preventive Services Task Force has to say and how it classifies (A through D, like school grades) each proposed screening procedure at www.ahcpr.gov/clinic/uspstfix.htm.

I’m sorry it’s so complicated, but it is important for you to know that. Many people, including physicians, misunderstand screening as black and white: all testing is good, positive tests warrant treatment, and all treatment cures all. None of those things, of course, is true.

Dan Onion: 293-2076, dkonion@gmail.com
 

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