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).

Related Articles


"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 January 30, 2015 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 January 30, 2015).

Share This


More From ScienceDaily



More Science & Society News

Friday, January 30, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Oxfam Calls for Massive Aid for Ebola-Hit West Africa

Oxfam Calls for Massive Aid for Ebola-Hit West Africa

AFP (Jan. 29, 2015) — Oxfam International has called for a multi-million dollar post-Ebola "Marshall Plan", with financial support given by wealthy countries, to help Guinea, Sierra Leone and Liberia to recover. Duration: 01:10 Video provided by AFP
Powered by NewsLook.com
Tesla 'Insane Mode' Gives Unsuspecting Passengers the Ride of Their Life

Tesla 'Insane Mode' Gives Unsuspecting Passengers the Ride of Their Life

RightThisMinute (Jan. 29, 2015) — If your car has an "Insane Mode" then you know it&apos;s fast. Well, these unsuspecting passengers were in for one insane ride when they hit the button. Tesla cars are awesome. Video provided by RightThisMinute
Powered by NewsLook.com
Now Bill Gates Is 'Concerned' About Artificial Intelligence

Now Bill Gates Is 'Concerned' About Artificial Intelligence

Newsy (Jan. 29, 2015) — Bill Gates joins the list of tech moguls scared of super-intelligent machines. He says more people should be concerned, but why? Video provided by Newsy
Powered by NewsLook.com
Are We Winning The Fight Against Ebola?

Are We Winning The Fight Against Ebola?

Newsy (Jan. 29, 2015) — The World Health Organization announced the fight against Ebola has entered its second phase as the number of cases per week has steadily dropped. Video provided by Newsy
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:

Strange & Offbeat Stories

 

Science & Society

Business & Industry

Education & Learning

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