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Research

Ratio measures in leading medical journals: structured review of accessibility of underlying absolute risks

BMJ 2006; 333 doi: https://doi.org/10.1136/bmj.38985.564317.7C (Published 14 December 2006) Cite this as: BMJ 2006;333:1248
  1. Lisa M Schwartz, associate professor of medicine1,
  2. Steven Woloshin, associate professor of medicine1,
  3. Evan L Dvorin, instructor of medicine2,
  4. H Gilbert Welch, professor of medicine1
  1. 1Veteran Affairs Outcomes Group, White River Junction, VT 05009, USA
  2. 2Dartmouth Medical School, Hanover, NH
  1. Correspondence to: S Woloshin steven.woloshin{at}dartmouth.edu
  • Accepted 29 August 2006

Abstract

Objective To examine the accessibility of absolute risk in articles reporting ratio measures in leading medical journals.

Design Structured review of abstracts presenting ratio measures.

Setting Articles published between 1 June 2003 and 1 May 2004 in Annals of Internal Medicine, BMJ, Journal of the American Medical Association, Journal of the National Cancer Institute, Lancet, and New England Journal of Medicine.

Participants 222 articles based on study designs in which absolute risks were directly calculable (61 randomised trials, 161 cohort studies).

Main outcome measure Accessibility of the absolute risks underlying the first ratio measure in the abstract.

Results 68% of articles (150/222) failed to report the underlying absolute risks for the first ratio measure in the abstract (range 55−81% across the journals). Among these articles, about half did report the underlying absolute risks elsewhere in the article (text, table, or figure) but half did not report them anywhere. Absolute risks were more likely to be reported in the abstract for randomised trials compared with cohort studies (62% v 21%; relative risk 3.0, 95% confidence interval 2.1 to 4.2) and for studies reporting crude compared with adjusted ratio measures (62% v 21%; relative risk 3.0, 2.1 to 4.3).

Conclusion Absolute risks are often not easily accessible in articles reporting ratio measures and sometimes are missing altogether—this lack of accessibility can easily exaggerate readers' perceptions of benefit or harm.

Footnotes


  • Embedded Image
    The data extraction form and calculations carried out by coders are on bmj.com

  • Contributors: LMS and SW analysed the data and wrote the first draft. They contributed equally to this project and the order of their names is arbitrary. HGW participated in the design of the analyses and made important contributions to the presentation of the work. ELD participated in design, data collection, and analyses. SW is the guarantor.

  • Funding: SW and LMS were supported by Veterans Affairs career development awards in health services research and development and Robert Wood Johnson generalist faculty scholar awards. This study was supported by a grant from the National Cancer Institute (R01CA104721) and from a research enhancement award from the Department of Veterans Affairs. The views expressed here do not necessarily represent the views of the Department of Veterans Affairs or the United States government.

  • Competing interests: None declared.

  • Ethical approval: Not required.

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