Assessment of Spin in the Abstracts of Randomized Controlled Trials in Dental Caries with Statistically Nonsignificant Results for Primary Outcomes: A Methodological Study.

The study aimed to assess the prevalence of spin in the titles and abstracts of RCTs in dental caries with statistically nonsignificant primary outcomes and to assess the risk indicators which may be associated with spin. Any original publication reporting a two-arm RCT in dental caries with clearly identified statistically nonsignificant primary outcomes published from January 1, 2015 until October 28, 2022 were included. PubMed was searched electronically to identify the eligible publications. The prevalence of spin in titles and abstracts were assessed and categorized into spin patterns based on a pre-determined classification scheme. The association between spin and the potential risk indicators at study, author, journal, institutional, and national level was assessed. A total of 234 eligible RCT publications were included. The prevalence of spin in the titles and abstracts was 3% (95%CI: 2% to 6%) and 79% (95%CI: 74% to 84%), respectively. The most common spin patterns in the results and conclusion sections, respectively, were results focusing on statistically significant within-group comparisons (23%), and conclusions focusing only on statistically significant results without acknowledgment of statistically nonsignificant results for the primary outcomes (26%). The spin was significantly associated with number of study centers (single-center vs. multicenter) (OR=2.131; 95%CI: 1.092 to 4.158; P=0.03), trial designs (non-parallel designs vs. parallel designs) (OR=0.395; 95%CI: 0.193 to 0.810; P=0.01), and overall H index of institutions for last authors (OR=0.998; 95%CI: 0.996 to 0.999; P<0.01), while it was not significantly associated with the other indicators. In the RCT publications with statistically nonsignificant results for primary outcomes in dental caries, the prevalence of spin may be low in the titles but high in the abstracts. Single-center studies with parallel designs and a lower overall H index of institutions for last authors may be more likely to have spin in the abstracts.