HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lazarus, R. M Search for Related Content PubMed PubMed Citation Articles by Lazarus, R. M Agricola Articles by Lazarus, R. M

Definition of sensitivity and specificity

Faculty of Medicine University of Sydney, A27 Camperdown, NSW 2006 Australia E-mail: rossl{at}med.usyd.edu.au

Dear Sir:

I noticed a technically incorrect definition in an otherwise interesting and potentially important article published recently in the Journal (1). The authors state in the introduction that "Sensitivity (proportion of subjects classified as `positive' by both the screening and reference tests) and specificity (proportion of subjects classified as `negative' by both tests) are calculated..." The wording "proportion of subjects" implies that the total number of subjects was the denominator.

Reference to any standard epidemiologic text will reveal that sensitivity is correctly and unambiguously defined as the proportion of reference test positive (diseased) subjects who test positive with the screening test. Note that the denominator is the number of reference test positive subjects, not the total number of subjects. Similarly, specificity is defined as the proportion of reference test negative (healthy) subjects who test negative with the screening test. Judging from the results, it seems likely that the authors used the correct denominator, but readers should be aware that the text is not technically correct.

REFERENCES

1. Taylor RW, Keil D, Gold EJ, Williams SM, Goulding A. Body mass index, waist girth, and waist-to-hip ratio as indexes of total and regional adiposity in women: evaluation using receiver operating characteristic curves. Am J Clin Nutr 1998;67:44–9[Abstract]

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lazarus, R. M Search for Related Content PubMed PubMed Citation Articles by Lazarus, R. M Agricola Articles by Lazarus, R. M