Single-subject research design: recommendations for levels of evidence and quality rating.

The aim of this article is to present a set of evidence levels, accompanied by 14 quality or rigor questions, to foster a critical review of published single-subject research articles. In developing these guidelines, we reviewed levels of evidence and quality/rigor criteria that are in wide use for group research designs, e.g. randomized controlled trials, such as those developed by the Treatment Outcomes Committee of the American Academy for Cerebral Palsy and Developmental Medicine. We also reviewed methodological articles on how to conduct and critically evaluate single-subject research designs (SSRDs). We then subjected the quality questions to interrater agreement testing and refined them until acceptable agreement was reached. We recommend that these guidelines be implemented by clinical researchers who plan to conduct single-subject research or who incorporate SSRD studies into systematic reviews, and by clinicians who aim to practise evidence-based medicine and who wish to critically review pediatric single-subject research.