Not enough SPIRIT shown in the registration and reporting of orthodontic trial protocols

To reduce bias associated with selective reporting, the registration and publication of clinical trial protocols before or at the time of patient enrolment has been advocated. The aim of this investigation was to assess the frequency of registration and reporting adherence of orthodontic trial protocols pre- and post-introduction of the Standard Protocol Items Recommendations for Interventional Trials (SPIRIT) Statement.

Trial protocols registered in four online registries were sourced at two time periods: (1 January 2010-1 January 2013) and (1 January 2017-1 January 2021). Protocols were screened and data extracted, in duplicate and independently. The reporting adherence of each protocol was assessed in relation to the thirty-three item SPIRIT statement. Fisher's exact test was used to determine associations between time periods and trial protocol characteristics. Median regression was implemented to assess potential associations between the percent score per protocol and protocol characteristics.

A total of 100 protocols were analysed. Thirty-three and sixty-seven protocols were registered in the first and second time periods, respectively. An association between period and the timing of registration (prospectively or retrospectively) (P < 0.001) and funding source (University or Company) (P < 0.001) was evident. Overall, 25 of the 33 (75.5%) SPIRIT statement items were not reported in either timeframe. The median percent reporting quality score was 26.9 (IQR 6.9). The type of registry was associated with percent scores and published studies received better percent scores compared to unpublished studies and academic or private protocol submissions.

There is a general lack of awareness of the importance and relevance of the SPIRIT statement. Registration of orthodontic trial protocols has apparently improved; however, 75.5% SPIRIT statement items were not reported in either study time period. The registration and reporting of orthodontic trial protocols should be advocated to circumvent issues relating to selective reporting and outcome reporting bias.