Screening Systems


Science, or at least the scientific method, can disappoint can’t it? We are informed -assured- that something is correct, the right thing to believe, and then with the passage of time and the arrival of new data must suddenly disavow that ‘Truth’ and start all over again. The comforting feeling that we have at last apprehended the underlying essence of something is torn away, leaving us with yet another useless fragment: a wide tie in a narrow-tie world… And the change, not fully understood, is apt to leave us bewildered and suspicious that nobody really understood it in the first place -not even those in charge. We are short-term creatures and our lives are brief; certainty is a luxury we long to indulge. A longer view of things is usually difficult and often opaque so a whole generation will espouse one thing, but the next another.

Medicine is not exempt. We spent a lot of time educating people -and governments- that a yearly health check-up was a good investment of time and resources: it would diagnose conditions at an earlier stage when treatment would likely be more successful and less expensive. It would save lives, save dollars; it was, and is, intuitively appealing. After all, a car needs periodic oil changes and during the process the mechanic might notice a tire that is abnormally worn, or a pipe that is almost rusted through; why would we be any different?

It’s a good question, and one with which I have struggled as well. And yet studies have suggested that although the occasional asymptomatic condition may be detected for which treatment, or at least counselling with follow-up would be indicated -things like hypertension, diabetes, cervical cell abnormalities detected by Pap smears or breast lumps with mammography come to mind- the inevitability of falsely positive tests often lead to far more extensive -and expensive- investigations that go nowhere. The yearly checkup, in other words, is being repudiated, despite its visceral appeal.

I remember when I was an intern and a new process was introduced that allowed multiple tests to be performed on a single sample of blood. One ordered, say, a hemoglobin to investigate a patient suspected of having anemia but as well as getting the hemoglobin, several other parameters were also reported. Statistically, there was a good chance that one of them would be abnormal -not necessarily the one being investigated, but merely a random error produced perhaps by medicine the patient was taking or food she had eaten, maybe even the time of month or hormone status. But it couldn’t be ignored, so further investigations would be undertaken -usually unnecessarily. The hospital continued to use the systemic multiple analysis on the blood tests, but soon realized that it made more sense to report only the entity requested. False positives can be a problem.

People become accustomed to certain screening systems, too; the programs become self-evidently appropriate, and any change to them is resisted as being either mean-spirited, or short-sighted. Prostate Specific Antigen testing, Mammography, and even Pap smear screening have all come under scrutiny of late. False positives, and even false negatives have been implicated as problems associated with undo reliance on them.

Take Pap smears, for example. Recommendations have varied over the years and jurisdictions, but the idea was that since cervical cancer was once so prevalent and deadly, it made sense to try to detect abnormal cells as soon as possible in a woman’s life. Suspicions that it was somehow associated with sex lead to the suggestion that Pap smears be started soon after she was sexually active -often within three years. Then how often? Well the recommendation in my center -assuming the first Pap was normal- was to repeat them once a year for three years and then every two years thereafter if they stayed normal. It seemed an entirely appropriate and reasonable approach at the time, so the public was educated accordingly. It became a widely accepted and normative routine and embedded itself within the public psyche: a woman needed regular Pap smears, and to wait too long between tests courted disaster. Hard to argue against that.

Until, of course, it was realized that certain subtypes of the Human Papilloma Virus (HPV) were responsible for cervical cancers and that young people often seemed to be able to mount an immune response to them without the need for treatment. So it became apparent that Pap smear testing too early in a woman’s life might lead to unnecessary interventions and the possibility of complications, not to mention the ever-attendant anxiety. Therefore the recommendations were amended (in some centers anyway): Pap smear screening might best be commenced at 21 years of age, and not shortly after sexual activity began. Many women did not feel comfortable with this approach, either for their daughters, or themselves, for that matter. More frequent was better, even if it led to further investigations such as microscopic examination and biopsies of the cervix (Colposcopy) that might prove negative. We need handles to grasp, doors that open; we need something we can trust. And they had been assured they could trust a regular regime of Pap smears. After all, it had certainly reduced the incidence of cervical cancer in the population. Once again hard to argue.

And now, yet again, it changes. If HPV is required to cause cervical cells to become abnormal, and the usual time for this to occur can be measured in years after the infection, wouldn’t it make sense to lengthen the interval for screening to take this into account -every five years, say? Maybe co-test with a Pap smear at the same time to make sure that abnormal cells hadn’t been brewing there for a while and then apply an algorithm to account for discrepant results? Or perhaps give the nervous public a choice: Pap smears every three years, or HPV and Pap every five? But because transient HPV infections are statistically more likely to occur in younger women (immune differences or amount of sexual activity, possibly?) don’t offer HPV testing to women under 30 because that might lead to unnecessary investigations… Confusing? Scientifically justified, but emotionally difficult to swallow?

I raise these issues because, well, my patients do. It’s not a little thing to change a habit, especially one inculcated by the profession and then rescinded or at least amended after widespread acceptance –generational acceptance. It requires not a little humility to reveal that we have not yet arrived. But, Wisely and slow, they stumble who run fast: Shakespeare again seemed to understand. But, do we?

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