Advertisement

eJournal Archive Package (1962- 2003): Details on request.

A Ruler for Interpreting Diagnostic Test Results

Journal: Methods of Information in Medicine
Subtitle: A journal stressing, for more than 50 years, the methodology and scientific fundamentals of organizing, representing and analyzing data, information and knowledge in biomedicine and health care
ISSN: 0026-1270
Issue: 2005 (Vol. 44): Issue 1 2005
Pages: 124-126

A Ruler for Interpreting Diagnostic Test Results

M. Hellmich, W. Lehmacher

Institute of Medical Statistics, Informatics and Epidemiology, University of Cologne, Germany

Keywords

Bayes’ rule, nomogram, likelihood ratio

Summary

Objectives: Bayes’ rule formalizes how the pre-test probability of having a condition of interest is changed by a diagnostic test result to yield the post-test probability of having the condition. To simplify this calculation a geometric solution in form of a ruler is presented. Methods: Using odds and the likelihood ratio of a test result in favor of having the condition of interest, Bayes’ rule can succinctly be expressed as ”the posttest odds equals the pre-test odds times the likelihood ratio”. Taking logarithms of both sides yields an additive equation. Results: The additive log odds equation can easily be solved geometrically. We propose a ruler made of two scales to be adjusted laterally. A different, widely used solution in form of a nomogram was published by Fagan [2]. Conclusions: Whilst use of the nomogram seems more obvious, the ruler may be easier to operate in clinical practice since no straight edge is needed for precise reading. Moreover, the ruler yields more intuitive results because it shows the change in probability due to a given test result on the same scale.

You may also be interested in...

1.
J. Marienhagen, Ch. Eilles

Nuklearmedizin 2003 42 4: 129-134



 

Follow us...

 

 

Methods News

Focus Theme on "Big Data and Analytics in Healthcare" - Deadline Extension

The submission deadline for the Focus Theme on "Big Data and Analytics in Healthcare"...

Methods issue 4/2014

Medical informatics, biometry and epidemiology are closely related disciplines that contribute...

Call for Papers

A tremendous amount of heterogeneous and complex healthcare data is created from sources such as...

Methods issue 3/2014

Ambient assisted living and smart homes are important interdisciplinary fields of research in the...

Related Topics