A priori power considerations in orthodontic research: a 3 year meta-epidemiologic study.

AIM: To assess the prevalence of a priori power calculations in orthodontic literature and to identify potential associations with a number of study characteristics, including journal, year of publication and statistical significance of the outcome. MATERIALS AND METHODS: The electronic archives of four leading orthodontic journals with the highest impact factor (American Journal of Orthodontics and Dentofacial Orthopedics, AJODO; European Journal of Orthodontics, EJO; Angle Orthodontist, ANGLE; Orthodontics and Craniofacial Research, OCR) were assessed over a 3 year period until December 2018. The proportion of articles reporting a priori power calculations were recorded, and the association with journal, year of publication, study design, continent of authorship, number of centres and researchers, statistical significance of results and reporting of confidence intervals (CIs) was assessed. Univariable and multivariable regression were used to identify significant predictors. RESULTS: Overall, 654 eligible articles were retrieved, with the majority published in the AJODO (n = 246, 37.6%), followed by ANGLE (n = 222, 33.9%) and EJO (n = 139, 21.3%). A total of 233 studies (35.6%) presented power considerations a priori along with sample size calculations. Study design was a very strong predictor with interventional design presenting 3.02 times higher odds for a priori power assumptions compared to observational research [odds ratio (OR): 3.02; 95% CIs: 2.06, 4.42; P < 0.001]. CONCLUSIONS: Presentation of a priori power considerations for sample size calculations was not universal in contemporary orthodontic literature, while specific study designs such as observational or animal and in vitro studies were less likely to report such considerations.

Statistical testing against baseline in orthodontic research: a meta-epidemiologic study.

BACKGROUND/OBJECTIVES: To assess the prevalence of within-group comparisons from baseline to follow-up in published orthodontic articles and to identify potential associations between this statistical problem and a number of study characteristics. MATERIALS/METHOD: The most recent 24 issues of four leading orthodontic journals with highest impact factor (American Journal of Orthodontics and Dentofacial Orthopedics; AJODO, European Journal of Orthodontics; EJO, Angle Orthodontist; ANGLE, Orthodontics and Craniofacial Research; OCR) were electronically searched until December 31st 2017. The proportion of articles using comparisons against baseline and interpretation of findings according to within-group comparisons were recorded. The association of this practice with journal, year of publication, study design, continent of authorship, number of centres and researchers, statistical significance of results, and statistical analysis was tested. Univariable and multivariable modified Poisson regression were used to identify significant predictors. RESULTS: Overall, 339 articles were eligible for inclusion with the majority published in ANGLE (n = 157, 46%), followed by AJODO (n = 75, 22%), and EJO (n = 75, 22%). A total of 60 studies (18%) presented interpretation of their findings based on within-group comparisons against baseline in isolation. Statistical significance of the primary outcome was a very strong predictor of the prevalence of this flawed approach (RR: 2.33, 95% CIs: 1.22, 4.43; P = 0.01). LIMITATIONS: The effect of time since publication was not addressed. CONCLUSIONS/IMPLICATIONS: Statistical testing and interpretation within groups is prevalent in orthodontic research. Endorsement of accurate conduct and reporting of statistical analyses and interpretation of research findings is important in order to promote optimal inferences to support clinical decision-making.