Although randomised controlled trials (RCTs) are the cornerstone of evidence-based medicine, studies that evaluate multiple crossovers between intervention and comparator in a single patient, or ‘n-of-1 trials’, can help to inform personalised treatment decisions. N-of-1 trials rigorously measure intervention effects for individuals and can generate valuable data in situations where RCTs are not feasible or appropriate, such as in rare diseases or when treatment effects are heterogeneous. Well conducted n-of-1 trials can also provide a source of population data for meta-analyses, important for conditions where there is little RCT evidence.
In 2013, the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) statement was released, providing evidence-based recommendations for the minimum content required in a published clinical trial protocol. An extension to these guidelines has recently been published in The BMJ by Dr Antony J Porcino and colleagues. The SPIRIT extension for n-of-1 trials (SPENT) provides guidance on the development and publishing of n-of-1 trial protocols to improve completeness and transparency.
The SPENT guidelines present the minimum content needed for complete and transparent reporting of n-of-1 trial protocols.
SPENT contains 14 extension items specific to n-of-1 trials, a checklist for n-of-1 trial protocol abstracts, and additional guidance for eight SPIRIT items providing information tailored to the n-of-1 trial context. To ensure concordance between the reporting of trial protocols and results, SPENT was developed in line with the CONSORT extension for n-of-1 trials (CENT) reporting guidelines.
The authors highlight that many aspects of n-of-1 trials are the same as parallel-group RCTs and, as such, many aspects of SPIRIT apply to SPENT. Stakeholders and reviewers are strongly encouraged to adopt SPENT to increase the standardisation, completeness and comparability of n-of-1 trial protocols. The authors conclude that increased uptake of SPENT will improve the quality of these protocols, their subsequent review and use, and ultimately, the resulting trial.