This Article  • Full text  • PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Citation map  • Citing articles on HighWire  • Contact me when this article is cited  Related Content  • Related articles  • Similar articles in JAMA  Topic Collections  • Journalology/ Peer Review/ Authorship  • Statistics and Research Methods  • Randomized Controlled Trial  • Alert me on articles by topic  Social Bookmarking   What's this?

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

To the Editor: The article by Dr Ioannidis¹ reported that it is not uncommon for highly cited studies of clinical interventions and their outcomes to be contradicted by subsequent research. The author noted several possible factors for this finding, including study-to-study variability and publication bias.

An additional contributor to the observed discrepancy among study results concerns the meaning of the typical marker of research significance, the P value. The P value is the probability of a finding, assuming that there is in truth no effect; it is not simply the probability that there is no effect. As noted by Browner and Newman,² research studies are analogous to diagnostic tests and P values are like false-positive rates when what we really seek is akin to a positive predictive value.

A diagnostic test with high sensitivity and specificity may still be ineffective if disease prevalence is low. Similarly, a small P value . . . [Full Text of this Article]

Colin P. West, MD, PhD
west.colin@mayo.edu
Division of General Internal Medicine
Mayo Clinic College of Medicine
Rochester, Minn

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter     What's this?

RELATED ARTICLES

Contradictions in Highly Cited Clinical Research
Paul S. Heckerling
JAMA. 2005;294(21):2695.
EXTRACT | FULL TEXT  

Contradictions in Highly Cited Clinical Research
Peter Westfall and S. Stanley Young
JAMA. 2005;294(21):2695-2696.
EXTRACT | FULL TEXT  

Contradictions in Highly Cited Clinical Research—Reply
John P. A. Ioannidis
JAMA. 2005;294(21):2696.
EXTRACT | FULL TEXT  

Contradicted and Initially Stronger Effects in Highly Cited Clinical Research
John P. A. Ioannidis
JAMA. 2005;294(2):218-228.
ABSTRACT | FULL TEXT  

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Letter by Hamilton and Filardo Regarding Article, "Reduced Ventricular Volumes and Improved Systolic Function With Cardiac Resynchronization Therapy: A Randomized Trial Comparing Simultaneous Biventricular Pacing, Sequential Biventricular Pacing, and Left Ventricular Pacing"
Hamilton and Filardo
Circulation 2008;117:e14-e14.
FULL TEXT