Interventions to promote informed consent for patients undergoing surgical and other invasive healthcare procedures

Before patients have an operation or other invasive procedure (e.g. endoscopy) it is crucial for the healthcare professional to explain what the treatment involves, what alternatives exist and the risks and benefits of the different treatment options.  This process is known as ‘informed consent’ and aims to provide sufficient information to allow patients to understand their treatment options and to choose between them. 

Research suggests that when informed consent is obtained, the information provided by healthcare professionals is often unclear or insufficient, leading to misunderstanding, a worse treatment response and even litigation.  A number of interventions have been developed to improve the quality of information provided to patients, including written pamphlets, videos and websites.  It is unclear whether these interventions work in clinical practice. 

In this review we summarise studies of interventions designed to improve information delivery or to improve consideration of information for informed consent. 

We searched the scientific literature to identify randomised controlled trials (RCTs) of interventions designed to improve informed consent in clinical practice.  We wanted to determine primarily whether these interventions improved all components of ‘informed consent’ (understanding, deliberation and communication of decision).  Other individual outcomes of direct relevance to patients (e.g. recall/knowledge, understanding, satisfaction and anxiety), those related to healthcare professionals (e.g. ease of use of intervention, satisfaction) and system outcomes (e.g. cost, rates of procedural uptake) were also assessed. 

We included 65 studies involving a total of 9021 patients.  The studies varied according to the type of intervention, the procedure for which consent was sought, the clinical setting and the outcomes measured.  Most interventions were written or audio-visual.  Only one study assessed all the elements of informed consent, but the design was not robust; all other studies assessed only components of informed consent.  When the results of multiple studies were combined, we found that interventions improved knowledge of the planned procedure, immediately (up to 24 hours), in the short term (1 to 14 days) and the long term (more than 14 days).  Satisfaction with decision making was increased; decisional conflict was reduced; and consultation length may be increased. There were no differences between the intervention and control for the outcomes of generalised anxiety, and either anxiety or satisfaction associated with the consent process.

Limitations of the review include difficulties combining the results of studies due to variation in the procedures undergone by patients, the interventions used and outcomes measured.  This means that we are uncertain as to which specific interventions are most effective but pragmatic steps to improve information delivery and consideration of the information are likely to benefit patients.  

Authors' conclusions: 

Informed consent is an important ethical and practical part of patient care.  We have identified efforts by researchers to investigate interventions which seek to improve information delivery and consideration of information to enhance informed consent.  The interventions used consistently improve patient knowledge, an important prerequisite for informed consent.  This is encouraging and these measures could be widely employed although we are not able to say with confidence which types of interventions are preferable. Our results should be interpreted with caution due to the high levels of heterogeneity associated with many of the main analyses although we believe there is broad evidence of beneficial outcomes for patients with the pragmatic application of interventions. Only one study attempted to measure informed consent as a unified concept.

Read the full abstract...

Achieving informed consent is a core clinical procedure and is required before any surgical or invasive procedure is undertaken.  However, it is a complex process which requires patients be provided with information which they can understand and retain, opportunity to consider their options, and to be able to express their opinions and ask questions.  There is evidence that at present some patients undergo procedures without informed consent being achieved.


To assess the effects on patients, clinicians and the healthcare system of interventions to promote informed consent for patients undergoing surgical and other invasive healthcare treatments and procedures.

Search strategy: 

We searched the following databases using keywords and medical subject headings: Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 5, 2012), MEDLINE (OvidSP) (1950 to July 2011), EMBASE (OvidSP) (1980 to July 2011) and PsycINFO (OvidSP) (1806 to July 2011). We applied no language or date restrictions within the search. We also searched reference lists of included studies.

Selection criteria: 

Randomised controlled trials and cluster randomised trials of interventions to promote informed consent for patients undergoing surgical and other invasive healthcare procedures. We considered an intervention to be intended to promote informed consent when information delivery about the procedure was enhanced (either by providing more information or through, for example, using new written materials), or if more opportunity to consider or deliberate on the information was provided.

Data collection and analysis: 

Two authors assessed the search output independently to identify potentially-relevant studies, selected studies for inclusion, and extracted data. We conducted a narrative synthesis of the included trials, and meta-analyses of outcomes where there were sufficient data.

Main results: 

We included 65 randomised controlled trials from 12 countries involving patients undergoing a variety of procedures in hospitals. Nine thousand and twenty one patients were randomised and entered into these studies. Interventions used various designs and formats but the main data for results were from studies using written materials, audio-visual materials and decision aids. Some interventions were delivered before admission to hospital for the procedure while others were delivered on admission.

Only one study attempted to measure the primary outcome, which was informed consent as a unified concept, but this study was at high risk of bias.  More commonly, studies measured secondary outcomes which were individual components of informed consent such as knowledge, anxiety, and satisfaction with the consent process.  Important but less commonly-measured outcomes were deliberation, decisional conflict, uptake of procedures and length of consultation.

Meta-analyses showed statistically-significant improvements in knowledge when measured immediately after interventions (SMD 0.53 (95% CI 0.37 to 0.69) I2 73%), shortly afterwards (between 24 hours and 14 days) (SMD 0.68 (95% CI 0.42 to 0.93) I2 85%) and at a later date (15 days or more) (SMD 0.78 (95% CI 0.50 to 1.06) I2 82%). Satisfaction with decision making was also increased (SMD 2.25 (95% CI 1.36 to 3.15) I2 99%) and decisional conflict was reduced (SMD -1.80 (95% CI -3.46 to -0.14) I2 99%). No statistically-significant differences were found for generalised anxiety (SMD -0.11 (95% CI -0.35 to 0.13) I2 82%), anxiety with the consent process (SMD 0.01 (95% CI -0.21 to 0.23) I2 70%) and satisfaction with the consent process (SMD 0.12 (95% CI -0.09 to 0.32) I2 76%). Consultation length was increased in those studies with continuous data (mean increase 1.66 minutes (95% CI 0.82 to 2.50) I2 0%) and in the one study with non-parametric data (control 8.0 minutes versus intervention 11.9 minutes, interquartile range (IQR) of 4 to 11.9 and 7.2 to 15.0 respectively). There were limited data for other outcomes.

In general, sensitivity analyses removing studies at high risk of bias made little difference to the overall results.