Are we drawing the right conclusions from randomised placebo-controlled trials? A post-hoc analysis of data from a randomised controlled trial

Evaluation of the Effects of 660-nm and 810-nm Low-Level Diode Lasers on the Treatment of Dentin Hypersensitivity

Introduction: Dentin hypersensitivity is a common oral problem that occurs as a short and sharp pain. There are many techniques to treat this condition, the latest of which is laser treatment. The aim of this study was to evaluate the effect of two types of low-power diode lasers (660 nm and 810 nm) on dentin hypersensitivity in order to achieve an acceptable clinical application by adjusting the effective parameters. Methods: In this randomized, double-blind clinical trial, sensitive teeth of 7 patients were divided into three groups with a randomized matching method: group I, treated with 660-nm diode laser irradiation, group II, treated with diode laser 810-nm, and group III, the control group. Irradiation parameters for 660-nm and 810-nm diode lasers were the power of 30 mW and 100 mW respectively, in contact and continuous modes, perpendicular to the tooth surface with a sweeping motion. Treatments were carried out in four sessions at weekly intervals. The data obtained were analyzed with SPSS 22, using one-way repeated measures ANOVA and the LSD (least significant difference) test. The significance level was considered as P≤0.05. Results: There were no significant differences in visual analogue scale (VAS) score changes between the two laser groups after the intervention in the first, second and third weeks compared to the baseline (P>0.05). These changes in the fourth week were significantly higher in the 810-nm laser group compared to the 660-nm laser group (P=0.04), and in the 660-nm laser group, they were more than the control group (P=0.02). The mean VAS scores at 1-week, 1-month and 2-month postoperative intervals were significantly lower in the 810-nm laser group than in the 660-nm laser group, and in the 660-nm laser group, they were less than the control group (P<0.001). Conclusion: The use of 660-nm and 810-nm diode lasers with the power of 30 and 100 mW respectively for 120 seconds was effective in reducing pain in patients with dentin hypersensitivity. However, the effect of the 810-nm laser on reducing the dentin hypersensitivity was more long-lasting than that of the 660-nm laser.

[What place for placebo in clinical trials conducted on psychiatric patients?]

Placebo effect remains a crucial issue in current clinical trials. Most clinical trials rely on the hypothesis of equivalent placebo response rates in both placebo and specific drug arms ("additive model"). But contrary to this dominant and rarely questioned hypothesis, several aspects may influence placebo response. A few recent meta-analyses and reviews have shown evidence for several clinical and methodological factors, which are able to modulate placebo response. In psychiatry research, placebo response has been mainly explored through antidepressant trials. In early clinical trials, drug-placebo differences were initially significant and robust. However, more recent clinical trials have not yielded similar results, and rather show narrowed antidepressant-placebo differences. Several factors may be involved in this absence of comparability: intrinsic properties of new antidepressants, changes in clinical criteria and classifications, symptomatic remission rather than global remission criteria, industrial and institutional constraints. Moreover, results from antidepressant trials (laboratory conditions) remain hardly fully transposable to clinical routine (ecological conditions).

Does the model of additive effect in placebo research still hold true? A narrative review

Personalised and contextualised care has been turned into a major demand by people involved in healthcare suggesting to move toward person-centred medicine. The assessment of person-centred medicine can be most effectively achieved if treatments are investigated using ‘with versus without’ person-centredness or integrative study designs. However, this assumes that the components of an integrative or person-centred intervention have an additive relationship to produce the total effect. Beecher’s model of additivity assumes an additive relation between placebo and drug effects and is thus presenting an arithmetic summation. So far, no review has been carried out assessing the validity of the additive model, which is to be questioned and more closely investigated in this review.

Initial searches for primary studies were undertaken in July 2016 using Pubmed and Google Scholar. In order to find matching publications of similar magnitude for the comparison part of this review, corresponding matches for all included reviews were sought.

A total of 22 reviews and 3 clinical and experimental studies fulfilled the inclusion criteria. The results pointed to the following factors actively questioning the additive model: interactions of various effects, trial design, conditioning, context effects and factors, neurobiological factors, mechanism of action, statistical factors, intervention-specific factors (alcohol, caffeine), side-effects and type of intervention.

All but one of the closely assessed publications was questioning the additive model. A closer examination of study design is necessary. An attempt in a more systematic approach geared towards solutions could be a suggestion for future research in this field.

Are placebo and drug-specific effects additive? Questioning basic assumptions of double-blinded randomized clinical trials and presenting novel study designs

Double-blinded randomized clinical trials (RCTs) assume that pharmacological interventions have drug-specific and unspecific components. Traditional RCTs postulate an additivity of these two components. In this review, we provide evidence from both clinical trials and experimental studies that questions this 'additive model'. Given that the evaluation of drug treatments in RCTs is based on the assumption of additivity, its violation has far-reaching consequences. Therefore, we discuss an interactive model that, in contrast to the additive model, considers interactions between placebo and drug-specific effects. Moreover, we discuss implications for future clinical trials and present novel study designs enabling researchers to consider the complex interplay of drug-specific and unspecific effects.

Placebo effects in medicine: A bibliometric analysis

Objective

It was the aim of this bibliometric analysis to identify all publications dealing with so-called 'context effects/placebo effects' to bring some organisation into the publication landscape of the past 35 years.

Design

An electronic database search was carried out in Pubmed from its inception to November 2011.

Participants

Already published articles and their participants were included.

Setting

This review was carried out at an academic institution.

Main outcome measures

Condition, country, year, journal, number of authors, type of publication and main focus of the publication.

Results

There are slight differences in the focus and the origin of research. Although the subject is multidimensional and covering all areas in healthcare, only a few research disciplines cover the field of placebo effects. The research field is shrinking as evident by the smaller number of researchers publishing in this field. It is suggested that the discussion regarding placebo and context effects is getting more homogenous and is turning into a specific field by itself. There is an increasing concentration of placebo effects being reproduced in experimental settings.

Conclusion

It is debatable whether the complexity of the broad range of what produces placebo effects can be successfully detected in a randomized controlled trial setting.

Context Effects in Western Herbal Medicine: Fundamental to Effectiveness?

Western herbal medicine (WHM) is a complex healthcare system that uses traditional plant-based medicines in patient care. Typical preparations are individualized polyherbal formulae that, unlike herbal pills, retain the odor and taste of whole herbs. Qualitative studies in WHM show patient-practitioner relationships to be collaborative. Health narratives are co-constructed, leading to assessments, and treatments with personal significance for participants. It is hypothesized that the distinct characteristics of traditional herbal preparations and patient-herbalist interactions, in conjunction with the WHM physical healthcare environment, evoke context (placebo) effects that are fundamental to the overall effectiveness of herbal treatment. These context effects may need to be minimized to demonstrate pharmacological efficacy of herbal formulae in randomized, placebo-controlled trials, optimized to demonstrate effectiveness of WHM in pragmatic trials, and consciously harnessed to enhance outcomes in clinical practice.

Placebo improvement in pharmacologic treatment of menopausal hot flashes: time course, duration, and predictors

OBJECTIVES

To characterize the time course, duration of improvement, and clinical predictors of placebo response in treatment of menopausal hot flashes.

METHODS

Data were pooled from two trials conducted in the Menopausal Strategies: Finding Lasting Answers to Symptoms and Health network, providing a combined placebo group (n = 247) and a combined active treatment group (n = 297). Participants recorded hot flash frequency in diaries twice daily during treatment (Weeks 0-8) and subsequent follow-up (Weeks 9-11). The primary outcome variable was clinically significant improvement, defined as a 50% or greater decrease in hot flash frequency from baseline and calculated for each week in the study. Subgroups were defined a priori using standard clinical definitions for significant improvement and partial improvement. Clinical and demographic characteristics of the participants were evaluated as predictors of improvement.

RESULTS

Clinically significant improvement with placebo accrued each treatment week, with 33% significantly improved at Week 8. Of placebo responders who were improved at both Weeks 4 and 8, 77% remained clinically improved at Week 11 after treatment ended. Independent predictors of significant placebo improvement in the final multivariable model were African American race (odds ratio [OR] = 5.61, 95% confidence interval [CI] = 2.41-13.07, p < .001), current smokers (OR = 2.30, 95% CI = 1.05-5.06, p = .038), and hot flash severity in screening (OR = 1.45, 95% CI = 1.00-2.10, p = .047).

CONCLUSIONS

Clinically significant improvement with placebo accrued throughout treatment with a time course similar to improvement with active drug. A meaningful number of participants in the placebo group sustained a clinically significant response after stopping placebo pills. The results suggest that nonspecific effects are important components of treatment and warrant further studies to optimize their contributions in clinical care.

Randomised controlled trials may underestimate drug effects: balanced placebo trial design

Background

It is an inherent assumption in randomised controlled trials that the drug effect can be estimated by subtracting the response during placebo from the response during active drug treatment.

Objective

To test the assumption of additivity. The primary hypothesis was that the total treatment effect is smaller than the sum of the drug effect and the placebo effect. The secondary hypothesis was that non-additivity was most pronounced in participants with large placebo effects.

Methods

We used a within-subject randomised blinded balanced placebo design and included 48 healthy volunteers (50% males), mean (SD) age 23.4 (6.2) years. Experimental pain was induced by injections of hypertonic saline into the masseter muscle. Participants received four injections with hypertonic saline along with lidocaine or matching placebo in randomised order: A: received hypertonic saline/told hypertonic saline; B: received hypertonic saline+lidocaine/told hypertonic saline; C: received hypertonic saline+placebo/told hypertonic saline+pain killer; D: received hypertonic saline+lidocaine/told hypertonic saline+pain killer. The primary outcome measure was the area under the curve (AUC, mm²) of pain intensity during injections.

Results

There was a significant difference between the sum of the drug effect and the placebo effect (mean AUC 6279 mm² (95% CI, 4936–7622)) and the total treatment effect (mean AUC 5455 mm² (95% CI, 4585–6324)) (P = 0.049). This difference was larger for participants with large versus small placebo effects (P = 0.015), and the difference correlated significantly with the size of the placebo effect (r = 0.65, P = 0.006).

Conclusion

Although this study examined placebo effects and not the whole placebo response as in randomised controlled trials, it does suggest that the additivity assumption may be incorrect, and that the estimated drug effects in randomised controlled trials may be underestimated, particularly in studies reporting large placebo responses. The implications for randomised controlled trials and systematic reviews need to be discussed.

Effect of frequent laser irradiation on orthodontic pain. A single-blind randomized clinical trial

OBJECTIVE

To analyze the effect of low-level laser therapy (LLLT) on perception of pain after separator placement and compare it with perceptions of control and placebo groups using a frequent irradiation protocol.

MATERIALS AND METHODS

Eighty-eight patients were randomly allocated to a laser group, a light-emitting diode (LED) placebo group, or a control group. Elastomeric separators were placed on the first molars. In the laser and LED groups, first molars were irradiated for 30 seconds every 12 hours for 1 week using a portable device. Pain was marked on a visual analog scale at predetermined intervals. Repeated measure analysis of variance was performed for statistical analysis.

RESULTS

The pain scores of the laser group were significantly lower than those of the control group up to 1 day. The pain scores in the LED group were not significantly different from those of the laser group during the first 6 hours. After that point, the pain scores of the LED group were not significantly different from those of the control.

CONCLUSIONS

Frequent LLLT decreased the perception of pain to a nonsignificant level throughout the week after separator placement, compared with pain perception in the placebo and control groups. Therefore, LLLT might be an effective method of reducing orthodontic pain.

[Placebo response: in studies on pain and under other clinical conditions]

This contribution compares unexplained essential questions regarding the placebo response with current empirical evidence: (1) Are the placebo response rates equivalent in the groups treated with medication or placebo? Very little evidence has been gathered to support this generally accepted additivity while some findings negate its validity. (2) Is the placebo response a function of the probability of receiving medication or placebo? There are indications that the number of study groups included in a trial determines the level of placebo and medication response. (3) How great is the placebo response in trials that directly compare a (new) medication with one that for example is already on the market? There are indications that such comparative studies produce higher placebo response rates. (4) How high is the placebo response rate in everyday clinical practice--or does the response to a medication in trials substantiate the effect of the medication in everyday clinical practice?

Placebo responses and placebo effects in functional bowel disorders

The nature and determinants of the placebo response are widely unknown, as are the underlying psychological and biological mechanisms. Placebo response rates in functional bowel disorders (functional dyspepsia, irritable bowel syndrome) trials are similar to those in nonintestinal pain conditions and are comparable with other organic gastrointestinal diseases (duodenal ulcer, inflammatory bowel diseases). In this narrative review, different methodologies (meta-analyses, reanalyses, and experimental setups) are discussed that have been applied to the study of the placebo response in functional dyspepsia and the irritable bowel syndrome.

The placebo response in clinical trials: more questions than answers

Meta-analyses and re-analyses of trial data have not been able to answer some of the essential questions that would allow prediction of placebo responses in clinical trials. We will confront these questions with current empirical evidence. The most important question asks whether the placebo response rates in the drug arm and in the placebo arm are equal. This 'additive model' is a general assumption in almost all placebo-controlled drug trials but has rarely been tested. Secondly, we would like to address whether the placebo response is a function of the likelihood of receiving drug/placebo. Evidence suggests that the number of study arms in a trial may determine the size of the placebo and the drug response. Thirdly, we ask what the size of the placebo response is in 'comparator' studies with a direct comparison of a (novel) drug against another drug. Meta-analytic and experimental evidence suggests that comparator studies may produce higher placebo response rates when compared with placebo-controlled trials. Finally, we address the placebo response rate outside the laboratory and outside of trials in clinical routine. This question poses a serious challenge whether the drug response in trials can be taken as evidence of drug effects in clinical routine.

The placebo effect in rheumatology: new data

The placebo effect is often poorly understood or confused with evaluation bias or spontaneous improvement, particularly when study inclusion criteria select patients at the peak of their symptoms. Cerebral imaging studies have confirmed that the placebo effect exists, although it is now known to involve a combination of conditioned reflexes and reward anticipation. The magnitude of the placebo effect can be evaluated by randomly dividing patients into three groups, one of which receives no treatment at all; by crossover studies; or by the newly developed open-hidden study design. This last design has established that rebound effects can occur after placebo discontinuation, and other experiments have shown that anxiety is associated with a weaker placebo response. This anti-placebo effect of anxiety, similar to the nocebo effect, may involve the release of cholecystokinin. The strength of the placebo effect varies across procedures and joints. A marked placebo effect can be seen in rheumatology patients, as shown recently by two high-quality double-blind studies that found no difference between vertebroplasty and a sham procedure. Effective blinding is crucial both to obtain a strong placebo effect and to separate an intrinsic effect from a placebo effect. Beliefs of the patients and physicians regarding the active drug and the existence and strength of the placebo effect could also be usefully evaluated throughout clinical studies.