Featured Research

from universities, journals, and other organizations

Clinical trials with nonblinded outcome assessors have high observer bias

Date:
January 28, 2013
Source:
Canadian Medical Association Journal
Summary:
A new study of randomized clinical trials found significant observer bias toward a more beneficial treatment effect in nonblinded trials when the researcher knew the treatment being given to the participant.

A new study of randomized clinical trials found significant observer bias toward a more beneficial treatment effect in nonblinded trials when the researcher knew the treatment being given to the participant. The study is published in CMAJ (Canadian Medical Association Journal).

"Nonblinded assessors of subjective measurement scales outcomes in randomized clinical trials tended to generate substantially biased effect sizes," writes Dr. Asbjørn Hróbjartsson, The Nordic Cochrane Centre, Rigshospitalet Department, Copenhagen, Denmark, with coauthors.

Danish and French researchers conducted a systematic review of 24 randomized clinical trials with both blinded and nonblinded assessment of the treatment effects. This design enabled a direct and reliable comparison between blind and nonblind results. Sixteen trials (with 2854 patients) had subjective outcomes and were included in the final meta-analysis. Neurology, cosmetic surgery, cardiology, psychiatry, otolaryngology, dermatology, gynecology and infectious diseases were all represented.

"In some trials, conscientious nonblinded assessors may overcompensate for an expected bias in favour of the experimental intervention and paradoxically induce a bias favouring the control, whereas other trials will have fairly neutral assessors with no important bias. Thus, the degree of observer bias in trials with clearly predisposed outcome assessors is likely to be considerably higher than the mean we see here," write the authors. They suggest using blinded assessors in trials to remove this bias.

"Failure to blind outcome assessors in such trials results in a high risk of substantial bias," conclude the authors.


Story Source:

The above story is based on materials provided by Canadian Medical Association Journal. Note: Materials may be edited for content and length.


Journal Reference:

  1. Asbjørn Hróbjartsson, Ann Sofia Skou Thomsen, Frida Emanuelsson, Britta Tendal, Jørgen Hilden, Isabelle Boutron, Philippe Ravaud, Stig Brorson. Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors. CMAJ, 2013 DOI: 10.1503/cmaj.120744

Cite This Page:

Canadian Medical Association Journal. "Clinical trials with nonblinded outcome assessors have high observer bias." ScienceDaily. ScienceDaily, 28 January 2013. <www.sciencedaily.com/releases/2013/01/130128133856.htm>.
Canadian Medical Association Journal. (2013, January 28). Clinical trials with nonblinded outcome assessors have high observer bias. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2013/01/130128133856.htm
Canadian Medical Association Journal. "Clinical trials with nonblinded outcome assessors have high observer bias." ScienceDaily. www.sciencedaily.com/releases/2013/01/130128133856.htm (accessed July 31, 2014).

Share This




More Science & Society News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) — British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) — Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) — A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Texas Scientists Study Ebola Virus

Texas Scientists Study Ebola Virus

AP (July 30, 2014) — Scientists in Texas are studying the Ebola virus, which has killed more than 670 people across West Africa this year. Right now, the disease has no vaccine and no specific treatment, with a fatality rate of at least 60 percent. (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:  

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile iPhone Android Web
      Follow Facebook Twitter Google+
      Subscribe RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins