The N of 1 trials design in the rheumatic diseases

Recently the N of 1, or single case experimental trial design, has increased in popularity among physicians and therapists interested in assessing the usefulness of a therapeutic modality within a single subject [1, 2]. The techniques are not considered new; single case experimental designs have found acceptance and widespread use for many years in the behavioral sciences [3]. Additionally, experimental physiology and medicine have employed these methods extensively over the last few decades, although there is a relative paucity of articles in the clinical literature that report the results of N of 1 trials. There is a variety of design options possible for N of 1 studies, and the interested reader is referred to Reference 3 for a more comprehensive review of the topic. This paper will review a few of the major design options, with particular attention given to the alternating treatment design (ATD). The advantages and drawbacks of the N of 1 technique, with specific reference to the field of rheumatology, will be the main emphasis.