The fallacies of screening tests extend beyond false positives

Several years ago, during an annual mammogram, my wife, who is in her 40s, was told a mass had been found in one of her breasts. Anxious and uncertain, she had a biopsy, and we braced for the worst.

My father-in-law, when in his 50s, went through a similarly harrowing experience when a prostate specific antigen (PSA) test given during a routine physical exam came out positive, and he underwent a prostate biopsy.

Fortunately, both my wife and father-in-law were found to be victims not of cancer but of false positives. It’s a common outcome — about three of every 10 mammograms and about seven of every 10 positive PSA testsresult in false alarms. Like my wife and father-in-law, many people may feel that the short-term pain of these tests is worth the reassurance that they are cancer-free. But lately the idea that screening tests are a surefire weapon against cancer has been undermined.

New guidelines, new fears

We have been programmed to believe that early detection through screening saves lives. Seventy-five percent of men over the age of 50 have had a prostate specific antigen (PSA) test; 67 percent of women over the age of 40 have had a mammogram in the past two years; and 55 percent of women get a Pap smear every year.

New guidelines and studies, however, have raised new questions and re-ignited debate over whether these tests may in fact do more harm than good. Earlier this month, the U.S. Preventive Services Task Force (USPSTF), a government-appointed scientific advisory board, recommended against routine PSA tests to screen for prostate cancer. The same panel also suggested that a Pap test every three years is as good as an annual test. Two newly published studies suggest reducing the number of mammograms in women under 50; one went so far as to conclude that “most women with screen-detected breast cancer have not had their life saved by screening. They are instead either diagnosed early (with no effect on their mortality) or overdiagnosed.”

How can this be? We have relied on these tests for decades to screen for cancer in otherwise healthy individuals. The truth is that PSA, mammogram and the Pap smear are poor screeners — and always have been. The levels of prostate specific antigen — the marker for cancer — can be elevated for a variety of reasons, like a benign prostate enlargement or a prostate infection. A mammogram can be read as suspicious due to a cyst, a benign fluid collection; a Pap smear is often reported as abnormal due to abnormal cells caused by a local infection.

The fallacies of these screening tests extend beyond the false positives or excessive mistaken alerts. These tests frequently miss the diagnosis of cancer or result in false negatives. The PSA will be normal in two of every 10 patients with prostate cancer and the mammogram will be normal in two of every 10 patients with breast cancer. The Pap smear will miss cervical cancer in three of 10 patients.

The tests are also potentially harmful. They lead to subsequent testing such as a biopsy, which can cause complications such as infection or lead to treatment of a cancer that would not have otherwise caused any harm.

‘We need better tests’

It’s hard to argue with my wife’s plea: “We need better tests.” But until new screening methods are developed, we need to adjust our expectations of the ones we have. As Virginia Moyer, a professor at the Baylor College of Medicine and head of the USPSTS, puts it, we need to get away from the false notion that “if some prevention is good, then more is better.”

So what would “a better test,” as my wife puts it, look like? It should be accurate, inexpensive, easy to administer and noninvasive, like the HIV blood test, which is 99 percent accurate and costs only about $15. Researchers are pursuing a variety of improvements for cancer screening tests, including one for prostate cancer that tracks blood calcium levels following a PSA test and another that tests urine for a genetic marker. But such tests are years away from being available to the general public.

In the meantime, should we throw away the PSA test, mammography and the Pap smear? Absolutely not. But we should certainly rethink their administration — limiting these tests to those who may be at higher risk of cancers because of their age, family history or presenting symptoms.

The PSA test has more value in the urologist’s office than in the primary care doctor’s office. It is helpful in patients who have an abnormal rectal exam or a family history of prostate cancer. A routine mammogram saves lives both in women over 50 and younger women with a family history of breast cancer. And a Pap smear done regularly reduces the risk of cervical cancer incidence and mortality by at least 80 percent.

A case-by-case decision

We should also remember that guidelines are just that — recommendations. Doctors need to tailor them to each patient’s situation. When a patient is anxious and requests an inexpensive, noninvasive test, I am willing to agree to it, as long as the patient is informed about the limitations. The question is whether insurers and Medicare are willing to pay for such tests.

Ultimately, the new guidelines and studies add a wrinkle to the already complex medical decision-making process: Are we willing to undergo an imperfect screening test? Or should we forgo it?

My wife has elected to continue with mammograms in her 40s despite the new research. “But if I miss a year or two, I am less worried,” she said.

As for me, when I turn 50 in a few years, I plan to skip the PSA test.

Manoj Jain is an infectious disease physician and contributor to the Washington Post, where this article originally appeared.  He can be reached at his self-titled site, Dr. Manoj Jain.

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    the entire cancer algorithm has to change. screening may find early cancers, but not decrease cancer deaths. these lesions may actually regress or disappear. we do have an immunosurveillance system, as one explanation, or there may be a darwinian component that the malignant mutation can not survive because it lacks invasiveness, ability to generate neovascularization. focus has been on better imaging to detect abnormalities or more sensitive assay to quantitate lesser amounts. trouble is every new imaging creates a sea of abnormalities, reminds me of gulliver’s travels where all the giants have bad skin, magnify normality and get abnormality. we can demand better screening tests, but the public must not demand screening with the same mentality in mind and newer tests must be predicated on a better understanding of carcinogenesis. i was a “psa” screening victum, and i miss my prostate

    • Anonymous

      My co-worker’s cancer was diagnosed as “agressive”.

      You do not have to answer publically, but I do have some questions on PSA monitoring 1. Did you have a Family Physician digitally checking your prostate plus checking PSA annually to see if there was a trend upward overtime? 2. Was imaging done to see if there were any nodularity to the prostate over time to see if it had “agressive” changes? 3. Was a biopsy done of prostate before removal and did the biopsy reveal any agressive cancer? At what point were you referred to urologist or decision was made to be agressive instead of monitoring for “agressive changes”?

      The reason I ask is there is a push for PCPs to just be referral agents to specialists and also to stop doing annual exams at which time digital prostate exams are performed or check PSAs altogether.


        i was followed for 5 years by my internist with psa and digital exams. because of increasing psa, had ultrasound guided biopsy of gland twice showing chronic prostatitis (about 8 samples taken each time) then had third biopsy because of increase again in psa, this time cancer seen in 6/8 biopsy specimens. not sure whether “aggressive” can be applied to histology. i was followed by urologist concomitant with internist throughout period. after seeing cancer and age 57, chose to have open radical prostatectomy, nerve-sparing. final pathology had medium high gleeson score, not no vascular invasion


    • Anonymous

      200 mg additional selenium a day will decrease your breast cancer risk by 82%.  There are so many ways to decrease you cancer risk and at the same time be healthier.  Lets work at true prevention.  Not earlier detection. 

  • Ileana Balcu

    – My wife has elected to continue with mammograms in her 40s despite the new research. “But if I miss a year or two, I am less worried,” she said.Exactly! This is the good effect of these discussions and of the openness to accept that we really don’t know much. I am less worried too, both about missing an year or two of testing and about a false positive which is so much more common than cancer.

  • Anonymous

    “what people want” in the administration of tests is what they want in health care generally – a coherent program of care based on science; that is, treatment whose  efficacy might be continually be examined against an amassed body of evidence from all other like practices.

    Instead what we’re given by US clinicians currently is fragmented care based on what they “know” about their anecdote-generating practices, rather than on what their presently siloed data may reveal if effectively accumulated. 

    • Anonymous

      What a lot of healthcare academia and goverment wants is to get to as close of a one size fits all approach as possible as long as all outliers fall into low enough percetages.  They downplay the “art” of medicine which takes into account the whole person, the individual. Some would say that individuals must be sacrificed for the good of the many and use “evidence-based” theory as tyranny and the excuse to use lesser trained healthcare providers following a set of rules and God help the outlier that fails certain therapy and something else must be done. My co-worker is an outlier with demanding a mammogram before age 40 without a palpable lump or family history of Breast Ca and breast cancer in-situ was found before it had spread to rest of breast tissue or sentinal node. It was her primary care physician who knew her, and responded to her “gut feeling” that saved her breast and probably her life.

      • Violetta V

        If what she had was DCIS then neither you nor anybody else knows if it would’ve ever spread if remained undetected. It’s easy to say “mammogram saved my life” but statistically, in most of these cases, it didn’t make a difference. The cancer could’ve never spread or it could’ve grown so slowly that it would’ve still be treatable if detected later or it could indeed have saved her life. 

        • Anonymous

          “…neither you nor anybody else knows if it would’ve ever spread..”

          Exactly, that is why the mammogram, at least we have a way of screening that is not an invasive procedure to find out. Much better a false positive with needle core biopsy that is negative (had one) than lose a breast or die.

          Also your use of the word “statistically”… is what I am talking about. Let me put it this way, why take blood pressure readings on children? Statistacally the blood pressure is most of the time in normal range, but an elevated pressure may be indication of something more serious or may be a “false positive”. You do get those ‘ouliers” that have “white coat syndrome” which is a false positive and may cause the patient to undergo a few extra tests that may or may not be negative. When comparing to mammograms on most women to taking blood pressure on every pediatric visit does that “screening” save lives? At times yes, Does the fact that it is most of the time normal just make you want to quit doing it? Maybe, maybe not, what to do?

  • Anonymous

    According to my husband’s Naturopath with a Certified Cancer Specialty, many prostate cancers start growing after you start poking needles in it. 

  • Anonymous

    Check out the research on Zyflamend..  Precancerous Prostate Cells tend to either revert to normal or become very slow growing cancers when the patients take Zyflamend.  But, I guess since no one can make any money treating prostate cancer that never manifests itself, this healthy supplement will never be considered.  Cancer is big money and the pharmaceutical companies are not truly interested in preventing it.  Early detection is not prevention.  They used to say Prostate Cancer is a cancer that you will die with not from.  Of course our general health has deteriorated in the past 40 years, so that may be less so today. 

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