REPLY
Mammography and Palpable Breast Abnormalities
Karla Kerlikowske, MD
4 May 2004 | Volume 140 Issue 9 | Page 764
IN RESPONSE:
We appreciate Dr. Evans's correspondence and the opportunity to clarify the use of the term likelihood ratios in our paper. Likelihood ratios are being used more frequently by clinicians in clinical practice but are still not as familiar as the sensitivity and specificity of a diagnostic test. Sensitivity is calculated among diseased persons and specificity is calculated among nondiseased persons, whereas likelihood ratios are calculated using a given test result among diseased and nondiseased persons, as noted in the footnotes of our Tables 2, 3, and 5. As stated by Dr. Evans, the likelihood ratios reported in our article are calculated correctly for screening and diagnostic mammography and fine-needle aspiration biopsy, and a clear description of how to apply likelihood ratios for these tests in clinical practice is provided. We reference the source data (1) used to calculate likelihood ratios reported in our paper as well as the formulas, which are as follows.
Positive likelihood ratio = sensitivity/1 – specificity
Negative likelihood ratio = 1 – sensitivity/specificity
These formulas show that likelihood ratios are calculated as the probability that persons with the disease have a particular test result divided by the probability that persons without the disease have the same test result. Additional information on how to calculate likelihood ratios for a given test result can be found in a classic epidemiology text (2).
|
Author and Article Information
|
|---|
From San Francisco Veterans Affairs Medical Center, San Francisco, CA 94121.
1. Kerlikowske K, Grady D, Barclay J, Sickles EA, Ernster V. Likelihood ratios for modern screening mammography. Risk of breast cancer based on age and mammographic interpretation. JAMA. 1996;276:39-43. [PMID: 8667537].[Abstract]
2. Sackett DL, Haynes RB, Tugwell P. Clinical Epidemiology: A Basic Science for Clinical Medicine. 2nd ed. Boston, MA: Little, Brown; 1991:119.
About Letters
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
Top
Author & Article Info
References
Article
