Positive-outcome bias: comparison of emergency medicine and general medicine literatures.

Objective: The existence of positive-outcome bias in the medical literature is well established. Positive-outcome bias in two emergency medicine journals was compared with that found in two general medicine journals.

Methods: Published original contributions from Annals of Emergency Medicine, American Journal of Emergency Medicine, JAMA, and New England Journal of Medicine were reviewed. Articles were categorized as demonstrating a positive or negative outcome or showing no difference using new criteria. Descriptive articles were excluded.

Results: Of 700 articles reviewed, 177 emergency medicine and 211 general medicine articles met the study criteria. The emergency medicine journals had 142 articles (80%) with positive outcomes, 27 (15%) with negative outcomes, and 8 (5%) with no difference. The general medicine journals had 169 articles (80%) with positive outcomes, 33 (16%) with negative outcomes, and 9 (4%) with no difference. There was no significant difference between journal groups (chi-square; p = 0.99). The power of the study was 0.80 to detect a difference of 15% between groups with alpha set at 0.05.

Conclusion: There was no significant difference in the proportions of positive-outcome studies published in this sample of the emergency medicine literature compared with the general medicine literature. The potential impact of positive-outcome bias and methods of dealing with the problem are reviewed.