Skip to main content

Main menu

  • Home
  • Content
    • Current issue
    • Past issues
    • Early releases
    • Collections
    • Sections
    • Blog
    • Infographics & illustrations
    • Podcasts
    • COVID-19 Articles
  • Authors & Reviewers
    • Overview for authors
    • Submission guidelines
    • Submit a manuscript
    • Forms
    • Editorial process
    • Editorial policies
    • Peer review process
    • Publication fees
    • Reprint requests
    • Open access
    • Patient engagement
  • Members & Subscribers
    • Benefits for CMA Members
    • CPD Credits for Members
    • Subscribe to CMAJ Print
    • Subscription Prices
  • Alerts
    • Email alerts
    • RSS
  • JAMC
    • À propos
    • Numéro en cours
    • Archives
    • Sections
    • Abonnement
    • Alertes
    • Trousse média 2023
  • CMAJ JOURNALS
    • CMAJ Open
    • CJS
    • JAMC
    • JPN

User menu

Search

  • Advanced search
CMAJ
  • CMAJ JOURNALS
    • CMAJ Open
    • CJS
    • JAMC
    • JPN
CMAJ

Advanced Search

  • Home
  • Content
    • Current issue
    • Past issues
    • Early releases
    • Collections
    • Sections
    • Blog
    • Infographics & illustrations
    • Podcasts
    • COVID-19 Articles
  • Authors & Reviewers
    • Overview for authors
    • Submission guidelines
    • Submit a manuscript
    • Forms
    • Editorial process
    • Editorial policies
    • Peer review process
    • Publication fees
    • Reprint requests
    • Open access
    • Patient engagement
  • Members & Subscribers
    • Benefits for CMA Members
    • CPD Credits for Members
    • Subscribe to CMAJ Print
    • Subscription Prices
  • Alerts
    • Email alerts
    • RSS
  • JAMC
    • À propos
    • Numéro en cours
    • Archives
    • Sections
    • Abonnement
    • Alertes
    • Trousse média 2023
  • Visit CMAJ on Facebook
  • Follow CMAJ on Twitter
  • Follow CMAJ on Pinterest
  • Follow CMAJ on Youtube
  • Follow CMAJ on Instagram
News

Many doctors have distorted perceptions of the value of medical tests

Miriam Shuchman
CMAJ February 04, 2019 191 (5) E142-E143; DOI: https://doi.org/10.1503/cmaj.109-5695
Miriam Shuchman
Toronto, Ont.
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Figures & Tables
  • Responses
  • Metrics
  • PDF
Loading
Figure

The value of the prostate-specific antigen test is a divisive topic in medicine.

Image courtesy of jarun011/iStock

In 2014, the Canadian Task Force on Preventive Health Care recommended against using the prostate-specific antigen (PSA) test to screen for prostate cancer in healthy men, concluding that it results in substantial harms via biopsies and surgeries that can lead to infections, impotence or urinary incontinence, and does not save men’s lives. “Amazingly, despite thousands and thousands of patients included in randomized controlled trials, there is no mortality benefit associated with PSA testing, not a sliver,” said task force member Dr. Eddy Lang, head of emergency medicine at the University of Calgary. The task force urged doctors who offer the PSA test to discuss its “unclear benefits and substantial harms” with patients, rather than simply presenting it as a tool for cancer screening.

A few years later, a survey of family doctors in the Barrie region of Ontario discovered that the task force recommendations barely affected clinical practice. Most of the doctors responding to the survey gave the PSA test to patients and believed it was beneficial. The PSA test remains a divisive issue, and studies show many physicians’ perceptions of the benefits and harms of any given test are distorted. They typically overestimate the chance that a patient will benefit from testing and underestimate the chance that a test will lead to harms.

“The belief in early detection is like a creed; there are people who just can’t let go of that idea,” said Renée Pellerin, a Canadian journalist who interviewed physicians, scientists and advocates for a 2018 book, Conspiracy of Hope, on the debates over breast cancer screening. According to Lang, many doctors have been “fooled by the false premise that catching cancer early makes a difference in the outcome.”

The reasons doctors use harmful or low-value tests go beyond an attachment to cancer screening. “A test result is binary; it’s positive or negative, whereas, when you’re clinically assessing someone, it’s not binary,” said Dr. Robert Ohle, an emergency medicine physician and researcher at Health Sciences North in Sudbury, Ontario. He thinks doctors like the certainty a test appears to provide, but they often run into problems because they lack understanding of probabilities and percentages.

One example he gives is a patient arriving in an emergency room with dizziness, a common problem. To determine whether the patient is having a stroke or brain bleed, doctors often order a computed tomography (CT) scan. If the scan has no abnormal findings, they see it as changing the patient “from a low-risk to a no-risk.” Yet in the case of a person presenting with dizziness, the value of a CT scan for determining whether a stroke is in progress is no better than flipping a coin. The CT scan can actually make the situation worse by falsely reassuring doctors, who may then miss a stroke.

Computed tomography also exposes patients to cancer-causing ionizing radiation, but doctors may discount that risk. Said Ohle, “It’s very difficult to conceptualize what a slight increased risk of a cancer in twenty years’ time means, versus the risk of missing a diagnosis today.”

The problem of unnecessary CT scans is especially concerning in children’s hospitals, because radiation’s cancer-causing effects may be more likely in children. But doctors fear missing important injuries, so they order CT scans even when the chance of a positive finding is low.

“From a public health point of view, if we were doing millions of CT scans, there would be a potential we were creating new cancers in children,” said Dr. Neil Merritt, director of pediatric trauma at the Children’s Hospital of Western Ontario. Use of CT scans in children has declined over the past few years but they’re still overused in the trauma setting, he said, because imaging studies without ionizing radiation, such as magnetic resonance imaging or emergency ultrasound, are harder to access.

Algorithms to assist in determining which patients actually need imaging don’t always help, since physicians may not follow them, as happened with the Canadian CT Head Rule. Designed to enable emergency physicians to be more selective when referring adults with minor head injuries for CT, it actually increased the number of scans obtained, according to a 2010 study, possibly because of emergency room crowding.

Merritt thinks the solution could be “clinical decision support” via the electronic health record. “So if you had a trauma patient roll into the bay, you’d be able to enter the information and right away determine whether or not this patient has a high risk of having some finding on their CT scan, and therefore make an informed decision.” But he acknowledges that decision support at that level is in its infancy in Canada.

Another strategy is to engage and empower patients, whom doctors consider a big driver of the problem through requests for unnecessary tests and treatments. The Choosing Wisely campaign has increased doctors’ awareness of the issue and is also trying to educate patients via pamphlets and signage in hospitals. Ohle thinks this could help because patients view risk differently than doctors. “Once you explain the probability of their getting harmed from the test versus the probability that they actually have the condition of interest, most patients are reasonable and they don’t want to expose themselves to harm unnecessarily,” he said.

Shared decision-making can be difficult to implement in a busy trauma centre, but it has a clear role in primary care. Canadian and American task forces recommend that any man considering screening for prostate cancer should have a chance to first discuss the pros and cons with a doctor. Said Lang, “If men knew what the risks were associated with [PSA] testing and how slim to nonexistent the benefits are, no man in his right mind would get tested.”

Footnotes

  • Posted on cmajnews.com on Jan. 15, 2019.

PreviousNext
Back to top

In this issue

Canadian Medical Association Journal: 191 (5)
CMAJ
Vol. 191, Issue 5
4 Feb 2019
  • Table of Contents
  • Index by author

Article tools

Respond to this article
Print
Download PDF
Article Alerts
To sign up for email alerts or to access your current email alerts, enter your email address below:
Email Article

Thank you for your interest in spreading the word on CMAJ.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
Many doctors have distorted perceptions of the value of medical tests
(Your Name) has sent you a message from CMAJ
(Your Name) thought you would like to see the CMAJ web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
Many doctors have distorted perceptions of the value of medical tests
Miriam Shuchman
CMAJ Feb 2019, 191 (5) E142-E143; DOI: 10.1503/cmaj.109-5695

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
‍ Request Permissions
Share
Many doctors have distorted perceptions of the value of medical tests
Miriam Shuchman
CMAJ Feb 2019, 191 (5) E142-E143; DOI: 10.1503/cmaj.109-5695
Digg logo Reddit logo Twitter logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like

Jump to section

  • Article
    • Footnotes
  • Figures & Tables
  • Responses
  • Metrics
  • PDF

Related Articles

  • No related articles found.
  • PubMed
  • Google Scholar

Cited By...

  • No citing articles found.
  • Google Scholar

More in this TOC Section

  • What to know about Omicron XBB.1.5
  • Could a flu shot push help curb pediatric hospitalizations?
  • Stalemate: What’s holding up a new health accord?
Show more News

Similar Articles

Collections

  • Topics
    • Patient safety & quality improvement
    • Screening & diagnostic tests

 

View Latest Classified Ads

Content

  • Current issue
  • Past issues
  • Collections
  • Sections
  • Blog
  • Podcasts
  • Alerts
  • RSS
  • Early releases

Information for

  • Advertisers
  • Authors
  • Reviewers
  • CMA Members
  • CPD credits
  • Media
  • Reprint requests
  • Subscribers

About

  • General Information
  • Journal staff
  • Editorial Board
  • Advisory Panels
  • Governance Council
  • Journal Oversight
  • Careers
  • Contact
  • Copyright and Permissions
  • Accessibiity
  • CMA Civility Standards
CMAJ Group

Copyright 2023, CMA Impact Inc. or its licensors. All rights reserved. ISSN 1488-2329 (e) 0820-3946 (p)

All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association or its subsidiaries.

To receive any of these resources in an accessible format, please contact us at CMAJ Group, 500-1410 Blair Towers Place, Ottawa ON, K1J 9B9; p: 1-888-855-2555; e: cmajgroup@cmaj.ca

Powered by HighWire