Article type
Year
Abstract
Background: Non-significant findings from sham/placebo-controlled trials are usually interpreted as the intervention being merely a placebo in spite of a range of influencing factors, including expectation. Although patients' belief or expectation regarding the benefit of treatment is regarded as a potentially important factor for yielding positive outcomes, data from clinical trials have shown inconsistent findings.
Objectives: To investigate the impact of patients' expectation regarding treatment on outcomes in randomised sham/ placebo-controlled trials reporting pain-related outcomes.
Methods: Electronic searching was conducted in Ovid MEDLINE in April 2011 to include: (1) randomized sham/placebo-controlled trials or secondary analysis of relevant RCT data; and (2) studies measuring general or treatment-specific expectations and the association with analgesic outcomes. We excluded laboratory-based experiments involving healthy volunteers or studies that did not report analgesic outcomes. As substantial heterogeneity between studies was expected, a qualitative review was conducted. Methodological quality assessment was performed using the modified Oxford quality scale.
Results: Of 174 studies, 5 reports including 6 RCTs and 4 secondary analyses of 7 relevant RCTs involving 2645 patients met our inclusion criteria. Interventions included acupuncture (n = 6), manipulation (n = 1), and drugs (n = 2) in mainly chronic pain conditions. All included studies were assessed as of highquality (≥4 points). At different time points, 7 studies measured patients' expectations or belief in the intervention, while the other 2 studies additionally sought physicians' expectations. Trials where no difference was found between tested intervention and placebo control, reported heterogeneous findings, i.e. high expectation does not always lead to better analgesic effect. Blinding success, how expectation is measured, and expectation measurement time-points varied across the studies, which may have contributed to conflicting results.
Conclusions: The current evidence doesnot fully support the notion that expectation produces less pain, calling for further investigation of this issue. A careful approach to interpreting non-significant findings of sham-controlled trials is needed in systematic reviews.
Objectives: To investigate the impact of patients' expectation regarding treatment on outcomes in randomised sham/ placebo-controlled trials reporting pain-related outcomes.
Methods: Electronic searching was conducted in Ovid MEDLINE in April 2011 to include: (1) randomized sham/placebo-controlled trials or secondary analysis of relevant RCT data; and (2) studies measuring general or treatment-specific expectations and the association with analgesic outcomes. We excluded laboratory-based experiments involving healthy volunteers or studies that did not report analgesic outcomes. As substantial heterogeneity between studies was expected, a qualitative review was conducted. Methodological quality assessment was performed using the modified Oxford quality scale.
Results: Of 174 studies, 5 reports including 6 RCTs and 4 secondary analyses of 7 relevant RCTs involving 2645 patients met our inclusion criteria. Interventions included acupuncture (n = 6), manipulation (n = 1), and drugs (n = 2) in mainly chronic pain conditions. All included studies were assessed as of highquality (≥4 points). At different time points, 7 studies measured patients' expectations or belief in the intervention, while the other 2 studies additionally sought physicians' expectations. Trials where no difference was found between tested intervention and placebo control, reported heterogeneous findings, i.e. high expectation does not always lead to better analgesic effect. Blinding success, how expectation is measured, and expectation measurement time-points varied across the studies, which may have contributed to conflicting results.
Conclusions: The current evidence doesnot fully support the notion that expectation produces less pain, calling for further investigation of this issue. A careful approach to interpreting non-significant findings of sham-controlled trials is needed in systematic reviews.