HCR -- Diagnostic vs Screening, Know the Difference

By John Ballard

As new guidelines and recommendations continue to be issued by a variety of experts everyone has more personal responsibility to stay up to date and well-informed. The current Komen vs Planned Parenthood brouhaha underscores the point. While most observers follow the narrative of the conflict and get pulled into the politics or public relations angles, it is easy to overlook a pox on both their houses.

Maggie Mahar tweets 

Planned Parenthood, like Komen, misleads young
women about breast cancer screening: hides
risks,hypes benefits  http://bit.ly/wblorq

The short (PDF, 9 pages) Cancer Letter to which she links has important information about the importance of screening, but balances the risks with the benefits. 

�All screening programmes do harm; some do good as well.� �Sir Muir Gray, chief knowledge officer of the UK National Health Service.

~~~~~~~~~~~~~~~

There are many disquieting aspects of the recent brouhaha regarding Komen for the Cure deciding to stop funding Planned Parenthood. First and foremost is the infusion of politics into issues of health policy. But there are others.

A story on the Planned Parenthood website is related by a 27-year old woman who �had no family history� of cancer and who discovered a lump in her breast. She �remembered Planned Parenthood.�

Clearly, having access to mammographic and eventually surgical and pathological assessment of her lump was a good thing. But in view of her symptoms the mammogram she got at Planned Parenthood was diagnostic and not screening. Every woman should have access to diagnostic mammograms, but whether Planned Parenthood is the appropriate place to offer them is less clear.

Regarding screening mammography, women in their twenties and thirties have never been shown to benefit. Indeed, the incidence of breast cancer is so low in this group�with or without screening�that millions and perhaps tens of millions of women would have to be randomized and followed up for extended periods to have any hope of showing a reduction in mortality�if there is one.

A 2009 USPSTF publication indicated that the �number needed to invite for screening to extend one woman�s life [is] 1,904 for women aged 40 to 49 years and 1,339 for women aged 50 to 59 years.�

Of course there is no abrupt change at age 50 and so these numbers are not constant over their respective intervals. The figure above interpolates within these intervals and extrapolates outside the intervals based on breast cancer incidence in the U.S.

?The takeaway to remember is the difference between diagnostic versus screening tests. This is not only true of x-rays but a raft of popular (uh, did I mention expensive?) tests in the modern medical toolbox. 

Aside from the expense, the less measurable effects of false positives, unneeded invasive procedures and the increased risk of plain old mistakes is part of the fallout. Previous posts here about PSA tests, MRI and CT Scans, colonoscopies and the whole crazy idea that more is better have become a recurrent theme for me. But every time I write another post I remember people I have known whose addiction to pill-pushing doctors and TV induced designer drugs have resulted in more harm and anxiety than benefits. Just a few days ago I posted something to Facebook about the overuse of statins and received a comment from a friend who had passed it to her Dad, saying she had told him for years that she thought he was over-medicating himself. He had all the side effects of long-term use, and of course his cholesterol numbers were good, but there is some question as to whether or not he would have received a bad diagnosis without it. 

They say being fat is bad but I can assure the reader as someone who has seen a lot of old people that there are still a lot of fat old people. Smoking is known to be bad for you and I quit smoking decades ago because I didn't like the odds. But odds is exactly what is at stake, not certainty. My family came from Kentucky where tobacco was an important cash crop and they both smoked unfiltered Lucky Strikes for forty years. Neither developed COPD or asthma, my father died in his seventies of a stroke and my mother lived past ninety. Yes, it was a lung tumor. It took seven decades to appear. Both of them played the odds and dodged the bullet. 

One more story. As a medical corpsman in Korea in the Sixties I saw civilians seeking access to GI medicine, especially pain killers and antibiotics. We were amused when they took them in advance, by the handful, to prevent pain and infection, but in many ways Americans have fallen into the same ignorant habits.

I'm not advocating ignoring screening tests. I am saying use good judgement. A screening test is diagnostic if there are signs or symptoms. And the "signs" may be nothing more than a family history. But absent any good reasons, routine screening can cost more than it's worth.