Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors

Hróbjartsson, Asbjørn; Thomsen, Ann Sofia Skou; Emanuelsson, Frida; Tendal, Britta; Hilden, Jørgen; Boutron, Isabelle; Ravaud, Philippe; Brorson, Stig

doi:10.1503/cmaj.120744

Cited by 398 publications

(185 citation statements)

References 48 publications

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“…Caution may be warranted though because training/experience may increase the assessors' stake in the outcome of their assessments. Although inter-observer 12 agreement may be enhanced by experience and training, this improvement may be at the expense of accuracy (Bernardin and Pence, 1980) and is no guarantee of absence of expectation bias (Hróbjartsson et al, 2013;Tuyttens et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…Yet, blinding outcome assessors is widely accepted as an important aspect of a good study design to avoid expectation bias, in particular when outcome measures are not clearly defined, hard to perceive and require human judgement, and when the assessor has an interest in the outcome of the study (Rosenthal, 1966;Savović et al, 2012;Schulz and Grimes, 2002). Meta-analyses provide evidence that non-blinded studies result in mostly exaggerated (but sometimes also obscured) treatment effects compared to blinded studies, presumably due to expectancy effects (Bello et al, 2012;Hróbjartsson et al, 2012Hróbjartsson et al, , 2013Schulz et al, 1995). Blinding of relevant people involved in the study (including e.g.…”

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confidence: 99%

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Opinion of applied ethologists on expectation bias, blinding observers and other debiasing techniques

Tuyttens

Stadig²,

Heerkens³

et al. 2016

Applied Animal Behaviour Science

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Opinion of applied ethologists on expectation bias, blinding observers and other debiasing techniques

Tuyttens

Stadig²,

Heerkens³

et al. 2016

Applied Animal Behaviour Science

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“…It has been speculated that there were different expectations among patients and investigators in the sham-controlled trials versus the open trial. [27]. In cancer patients only observational studies have reported data with VP.…”

Section: Discussionmentioning

confidence: 99%

Minimally invasive procedures for the management of vertebral bone pain due to cancer: The EAPC recommendations

et al. 2015

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Background: Image-guided percutaneous ablation methods have proved effective for treatment of benign bone tumors and for palliation of metastases involving the bone. However, the role of these techniques is controversial and has to be better defined in the setting of palliative care. Methods: A systematic review of the existing data regarding minimally invasive techniques for the pain management of vertebral bone metastases was performed by experts of the European Palliative Care Research Network. Results: Only five papers were taken into consideration after performing rigorous screening according to inclusion and exclusion criteria (low number of patients, retrospective series, proceedings). Discussion: According to the present data a recommendation should be made to perform kiphoplasty in patients with vertebral tumors or metastases. However, the strength of this recommendation was based on one randomized controlled study. Several weaknesses and low quality of study design were observed with other techniques. Conclusion: Further randomized controlled trials are required to improve the strength of evidence available to suggest these procedures on large scale. Until then, the balance of evidence favors the use of these procedures in a small select cohort of patients with severe and disabling back pain refractory to medical therapy.

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“…Other recent studies that have incorporated blinding to control confirmation bias have demonstrated surprising results in the placebo treatment groups [45,46]. A recent metaanalysis of 16 trials with subjective outcomes determined that non-blinded subjective outcomes were associated with exaggerated treatment effectiveness compared to blinded outcomes [47][48][49]. Additionally, the duration of confirmation bias is unclear in the literature.…”

Section: Confirmation Biasmentioning

confidence: 99%

Bias in cervical total disc replacement trials

Radcliff

Siburn

Murphy

et al. 2017

Curr Rev Musculoskelet Med

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Purpose of review Cervical disc replacement (CDR) has emerged as a motion-preserving alternative to anterior cervical discectomy and fusion in selected cases. Despite favorable literature, CDR is not universally accepted because of concerns regarding bias in the existing literature. The purpose of this review is to identify the possible biases in the disc replacement literature. Recent findings Recent studies that compare CDR and ACDF have demonstrated equivalent or superior outcomes, lower rates of secondary surgery, and equivalent safety at mediumand long-term follow-up. In our review, we identified four types of bias that may affect the CDR literature: publication bias, external validity, confounding bias, and financial conflicts of interest. Summary Bias, whether intentional or unintentional, can impact the interpretation and outcome of CDR studies. Recognition of this issue is critical when utilizing the existing literature to determine the efficacy of CDR and designing future studies.

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Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors

Cited by 398 publications

References 48 publications

Opinion of applied ethologists on expectation bias, blinding observers and other debiasing techniques

Opinion of applied ethologists on expectation bias, blinding observers and other debiasing techniques

Minimally invasive procedures for the management of vertebral bone pain due to cancer: The EAPC recommendations

Bias in cervical total disc replacement trials

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