The presence and characteristics of 'spin' among randomized controlled trial abstracts in orthodontics

Objectives: To identify the presence and characteristics of spin (using reporting strategies to distort study results and mislead readers) within randomized controlled trial (RCT) abstracts published in orthodontic journals, and to explore the association between spin and potentially related factors. Methods: A manual search was conducted to identify abstracts of RCTs with statistically non-significant primary outcomes published in five leading orthodontic journals between 2015 and 2020. Spin in the Results and Conclusions sections of each included abstract was evaluated and categorized according to pre-determined spin strategies. Logistic regression analyses were employed to explore the association between spin and relevant factors. Results: A total of 111 RCT abstracts were included, of which 69 (62.2 per cent) were identified with spin. In the Results section, 47 (42.3 per cent) abstracts had spin, and 'focusing on significant within-group comparison for primary outcomes' was the most frequent spin strategy. In the Conclusions section, 57 (51.4 per cent) abstracts presented spin, with the most common strategy being 'claiming equivalence or non-inferiority for statistically nonsignificant results'. According to multivariable logistic regression analysis, a significantly lower presence of spin was found in studies with international collaboration (odds ratio [OR]: 0.331, 95 per cent confidence interval [CI]: 0.120-0.912, P = 0.033) and trial registration (OR: 0.336, 95 per cent CI: 0.117-0.962, P = 0.042). Conclusion: The prevalence of spin is high among RCT abstracts in orthodontics. Clinicians need to be aware of the definition and presence of spin. Concerted efforts are needed from researchers and other stakeholders to address this issue.