Analysis of spin in vascular surgery randomized controlled trials with nonsignificant outcomes

Spin is the manipulation of language that distorts the interpretation of objective findings. The purpose of this study is to describe the characteristics of spin found in statistically nonsignificant randomized controlled trials (RCT) comparing carotid endarterectomy with carotid artery stenting for carotid artery stenosis (CS), and endovascular repair with open repair (OR) for abdominal aortic aneurysms (AAA).

A search of MEDLINE, EMBASE, and the Cochrane Controlled Register of Trials was performed in June 2020 for studies published describing AAA or CS. All phase III RCTs with nonsignificant primary outcomes comparing open repair with endovascular repair or carotid endarterectomy to carotid artery stenting were included. Studies were appraised for the characteristics and severity of spin using a validated tool. Binary logistic regression was performed to assess the association of spin grade to (1) funding source (commercial vs noncommercial) and (2) the publishing journal's impact factor.

Thirty-one of 355 articles captured were included for analysis. Spin was identified in 9 abstracts (9/18) and 13 main texts (13/18) of AAA articles and 7 abstracts (7/13) and 10 main texts (10/13) of CS articles. For both AAA and CS articles, spin was most commonly found in the discussion section, with the most commonly used strategy being the interpretation of statistically nonsignificant primary results to show treatment equivalence or rule out adverse treatment effects. Increasing journal impact factor was associated with a statistically significant lower likelihood of spin in the study title or abstract conclusion (β odds ratio, 0.96; 95% confidence interval, 0.94-0.98; P < .01); no significant association could be found with funding source (β odds ratio, 1.33; 95% confidence interval, 0.30-5.92; P = .71).

A large proportion of statistically nonsignificant RCTs contain interpretations that are inconsistent with their results. These findings should prompt authors and readers to appraise study findings independently and to limit the use of spin in study interpretations.