Misinterpreting Odds Ratio in the Articles Published in Korean Journal of Family Medicine

Abstract

BackgroundIn reporting results of case-control studies, odds ratios are useful methods of reporting findings. However, odds ratios are often misinterpreted in the literature and by general readers.MethodsWe searched all original articles which were published in the Korean Journal of Family Medicine from 1980 to May 2011 and identified those that report "odds ratios." Misinterpretation of odds ratios as relative risks has been identified. Estimated risk ratios were calculated when possible and compared with odds ratios.ResultsOne hundred and twenty-eight articles using odds ratios were identified. Among those, 122 articles were analyzed for the frequency of misinterpretation of odds ratios as relative risks. Twenty-two reports out of these 122 articles misinterpreted odds ratios as relative risks. The percentage of misinterpreting reports decreased over years. Seventy-seven reports were analyzed to compare the estimated risk ratios with odds ratios. In most of these articles, odds ratios were greater than estimated risk ratios, 60% of which had larger than 20% standardized differences.ConclusionIn reports published in the Korean Journal of Family Medicine, odds ratios are frequently used. They were misinterpreted in part of the reports, although decreasing trends over years were observed.

Nota epidemiológica: razón de ODDS (OR)

“…Además, analizaron 67 informes para comparar las razones de riesgo estimadas con las razones de Odds y en la mayoría de estos trabajos el OR sobrestimaba el RR. 23 Otra precaución que se debería tener frente al uso del OR, está relacionada con situaciones en las que se presentan una alta incidencia del resultado de interés, dado que se produce una sobreestimación progresiva del RR, en especial con eventos cuya frecuencia supera el 10%. 24 Es así como cuando la enfermedad es frecuente, el RR y el OR pueden D I S C U S I Ó N llegar a ser bastante diferentes 25 , lo cual fue descrito en la publicación de Chan S. y col. quien en una carta al editor ilustran la situación a partir de un estudio retrospectivo en el que se comparó dos grupos de pacientes con hernia inguinal tratados con una de dos técnicas quirúrgicas en el Hospital Militar Central de Lima, utilizando como medida de asociación el OR.…”

Comments on Statistical Errors for May Issue 2012

“…Kim et al 1) pointed out the misinterpretation of OR in the articles published in the Korean Journal of Family Medicine as RR and proposed the formula of Zhang and Yu, 2) …”

“…In this section, we would like to explain the properties of the relative risk (RR) and odds ratio (OR) which appeared in the article titled, "Misinterpreting odds ratio in the articles published in the Korean Journal of Family Medicine," published in March 2012 by Kim et al, 1) and the relationship between both measures in prospective and retrospective studies.…”