OBJECTIVES : The primary objective of this research is to outline the current landscape of literature pertaining to patient expectation of treatments and its relation to the placebo effect. Additionally, recommendations will be provided for considering patient expectation of treatment as a factor of the placebo response in designing and implementing patient-reported outcome measures (PROs) to support labeling claims.

METHODS : An initial hand search of relevant literature was reviewed prior to conducting a targeted literature review in MEDLINE® using the search terms “placebo” and “expectancy.” Results were restricted to the past 10 years and English language, and the process of “snowballing” was used to identify new articles. Each article selected for full review was qualitatively analyzed for common themes and key concepts regarding the relationship between expectancy, the placebo effect, and outcome measures. This information was extracted and reported by frequency of occurrence of each concept across articles.

RESULTS : A total of 57 abstracts were reviewed of which 36 articles were reviewed in full. The results indicated that expectancy is comprised of factors including verbal or written manipulation of expectations (72.2%); prior experience or classical conditioning (44.4%); the patient’s belief about the treatment, substance, or condition (41.7%); and positive or negative interactions with clinicians (19.4%). Eighteen PRO instruments related to patient expectation of treatment were identified, most of which were disease-specific. Additionally, given the placebo response on patient-based ratings can be substantial in pain studies, ten of the studies reviewed (27.8%) involved patients rating pain on scales, including expected pain (8.3%).

CONCLUSIONS : Assessing patient expectations is a promising approach to disentangling the magnitude of the placebo effect from the actual treatment benefit of an intervention, thus improving the sensitivity of outcome measures. It is recommended that sponsors consider measuring patient expectancy of treatment through the use of a PRO measure.