Risk of bias and magnitude of effect in orthodontic randomized controlled trials: a meta-epidemiological review

Bibliometric and visualized analysis of randomized controlled trials in orthodontics between 1991 and 2022

INTRODUCTION

In many evidence-based approaches to orthodontic research, randomized controlled trials (RCTs) represent authoritative evidence to identify rational therapeutics. This study aimed to perform mappings of bibliometric networks on orthodontic RCTs and summarize visual characteristics between 1991 and 2022.

METHODS

The articles were retrieved from the Web of Science Core Collection in October 2022 without an initial time limit. Only orthodontic RCTs were eligible. Some bibliometric tools (HistCite, VOSviewer, SCImago Graphica, and CiteSpace) were applied for visualized analysis. Data such as geography, productive institutions, hot articles, journals, authors, references, and keywords were extracted and summarized for analysis.

RESULTS

A total of 1122 orthodontic RCTs were searched. A total of 3841 authors from 1157 institutions in 65 countries published orthodontic RCTs. The United States (149) was the most prolific country, and the University of Sao Paulo (35) was the most productive institution. The American Journal of Orthodontics and Dentofacial Orthopedics (206) was the most popular journal for scholars. The visualization results of keyword co-occurrence identified 5 clusters: (1) tooth movement and auxiliary measures, (2) appliances and oral health, (3) orthodontic discomfort and symptomatic therapy, (4) periodontal disease in orthodontics and health maintenance, and (5) retention and relapse.

CONCLUSIONS

Over the past 31 years, publications and citations on orthodontic RCTs from the Web of Science Core Collection have increased notably across many countries, authors, and institutions. Recently, there has been a significant increase in the attention to orthodontic RCTs that focus on accelerating tooth movement.

Effects of chlorhexidine use on periodontal health during fixed appliance orthodontic treatment: a systematic review and meta-analysis

BACKGROUND

Proper oral hygiene and absence of periodontal inflammation is pre-requisite for orthodontic treatment. Chlorhexidine (CHX) is an established oral antiseptic used in the treatment of periodontal disease, but its role in orthodontic therapy is unclear.

OBJECTIVES

To assess the efficacy of adjunct use of CHX-containing products in maintaining gingival health among orthodontic patients with fixed appliances.

SEARCH METHODS

Five databases were searched without limitations up to August 2021.

SELECTION CRITERIA

Randomized clinical trials (RCTs) assessing Gingival Index (GI) (primary outcome), Plaque Index (PI), Bleeding Index (BI), or Pocket Probing Depth (PPD).

DATA COLLECTION AND ANALYSIS

Study selection, data extraction, and risk of bias assessment were done independently in duplicate. Random-effects meta-analyses of mean differences (MDs) or standardized mean differences (SMDs) with their 95% confidence intervals (CIs) were conducted, followed by sensitivity and Grades of Recommendations, Assessment, Development and Evaluation analysis.

RESULTS

Twenty RCTs (1001 patients) were included assessing CHX-containing mouthwashes (n = 11), toothpastes (n = 2), gels (n = 3), or varnishes (n = 4) compared to placebo/control (n = 19) or sodium fluoride-products (n = 4). In the short-term, CHX-containing mouthwash was associated with lower GI (n = 9; MD = -0.68; 95% CI = -0.97 to -0.38; P < 0.001; high quality), lower PI (n = 9; MD = -0.65; 95% CI = -0.86 to -0.43; P < 0.001; high quality), lower BI (n = 2; SMD = -1.61; 95% CI = -2.99 to -0.22; P = 0.02; low quality), and lower PPD (n = 2; MD = -0.60 mm; 95% CI = -1.06 to -0.14 mm; P = 0.01; low quality). No considerable benefits were found from the use of CHX-gel or CHX-varnish in terms of GI, PI, or PPD (P > 0.05/low quality in all instances). Use of a CHX-containing toothpaste was more effective in lowering PI (Heintze-index) than adjunct use of fluoride-containing mouthwash (n = 2; MD = -5.24; 95% CI = -10.46 to -0.02; P = 0.04), but not GI (P = 0.68) or BI (P = 0.27), while sensitivity analyses indicated robustness.

CONCLUSIONS

Adjunct use of CHX mouthwash during fixed-appliance treatment is associated with improved gingival inflammation, plaque control, and pocket depths, but caution is warranted and recommendations about CHX use during orthodontic treatment of children/adults should consider the heterogeneous patient response, cost-effectiveness, and potential adverse effects.

REGISTRATION

PROSPERO registration (CRD42021228759).

An artificial neural network (ANN) model for publication bias: a machine learning-based study on PubMed meta-analyses

Purpose

No study has investigated the effects of different parameters on publication bias in meta-analyses using a machine learning approach. Therefore, this study aims to evaluate the impact of various factors on publication bias in meta-analyses.

Design/methodology/approach

An electronic questionnaire was created according to some factors extracted from the Cochrane Handbook and AMSTAR-2 tool to identify factors affecting publication bias. Twelve experts were consulted to determine their opinion on the importance of each factor. Each component was evaluated based on its content validity ratio (CVR). In total, 616 meta-analyses comprising 1893 outcomes from PubMed that assessed the presence of publication bias in their reported outcomes were randomly selected to extract their data. The multilayer perceptron (MLP) technique was used in IBM SPSS Modeler 18.0 to construct a prediction model. 70, 15 and 15% of the data were used for the model's training, testing and validation partitions.

Findings

There was a publication bias in 968 (51.14%) outcomes. The established model had an accuracy rate of 86.1%, and all pre-selected nine variables were included in the model. The results showed that the number of databases searched was the most important predictive variable (0.26), followed by the number of searches in the grey literature (0.24), search in Medline (0.17) and advanced search with numerous operators (0.13).

Practical implications

The results of this study can help clinical researchers minimize publication bias in their studies, leading to improved evidence-based medicine.

Originality/value

To the best of the author’s knowledge, this is the first study to model publication bias using machine learning.

A methodological review with meta-epidemiological analysis of preclinical systematic reviews with meta-analyses

Systematic reviews and meta-analyses have been proposed as an approach to synthesize the literature and counteract the lack of power of small preclinical studies. We aimed to evaluate (1) the methodology of these reviews, (2) the methodological quality of the studies they included and (3) whether study methodological characteristics affect effect size. We searched MEDLINE to retrieve 212 systematic reviews with meta-analyses of preclinical studies published from January, 2018 to March, 2020. Less than 15% explored the grey literature. Selection, data extraction and risk of bias assessment were performed in duplicate in less than two thirds of reviews. Most of them assessed the methodological quality of included studies and reported the meta-analysis model. The risk of bias of included studies was mostly rated unclear. In meta-epidemiological analysis, none of the study methodological characteristics was associated with effect size. The methodological characteristics of systematic reviews with meta-analyses of recently published preclinical studies seem to have improved as compared with previous assessments, but the methodological quality of included studies remains poor, thus limiting the validity of their results. Our meta-epidemiological analysis did not show any evidence of a potential association between methodological characteristics of included studies and effect size.

A priori power considerations in Endodontic Research. Do we miss the timeline?

AIM

To record the prevalence of a priori power calculations in manuscripts published in three endodontic journals between 2018 and 2020 and detect further associations with a number of study characteristics including journal, publication year, study design, geographic region, number of centres and authors, whether the primary outcome pertained to a statistically significant effect and whether confidence intervals (CIs) were reported.

METHODOLOGY

The contents of the three leading endodontic journals with the highest impact factor (International Endodontic Journal, IEJ; Journal of Endodontics, JOE; and Australian Endodontic Journal, AEJ) were assessed from January 2018 to December 2020. The proportion of articles reporting a priori power calculations were recorded, and relevant associations as described above were assessed. Univariable and multivariable logistic regression were used to identify significant predictors, whilst interaction and linear trend effects were also considered.

RESULTS

A total of 716 original research articles were included. The vast majority were published in the JOE (417/716; 58.2%), followed by the IEJ (225/716; 31.4%) and the AEJ (74/716; 10.4%). Overall, a priori power considerations were reported in 243 out of 716 articles (33.9%). The IEJ presented 1.61 times higher odds for including a priori power considerations compared to JOE (adjusted odds ratio, OR = 1.61; 95%CI: 1.11, 2.34), whilst for the AEJ, the corresponding odds were 41% lower in comparison to JOE (adjusted OR = 0.59; 95%CI: 0.31, 1.14). For each additional year indicating more recent publication, the odds for adopting appropriate reporting practices for power considerations were increased by 64% (adjusted OR = 1.64; 95%CIs: 1.32, 2.04). There was strong evidence that interventional research was associated with 10.54 times higher odds for a priori considerations compared to observational study design (adjusted OR = 10.54; 95%CIs: 5.50, 20.19).

CONCLUSIONS

The high prevalence of failure to include a priori power considerations was indicative of suboptimal reporting in endodontic research, in the three endodontic journals analysed. Although the condition improved over time, efforts to incorporate a correct determination of the required sample size at the design stage for any future study should be endorsed by journal editors, authors and the scientific community.

The reporting quality of split-mouth trials in orthodontics according to CONSORT guidelines: 2015-19

OBJECTIVES

To assess the reporting quality of split-mouth trials (SMTs) in orthodontic journals, and to identify factors associated with better reporting.

MATERIALS AND METHODS

Seven leading orthodontic journals were hand searched for SMTs published during 2015-19. The CONSORT 2010 guideline and CONSORT for within-person trial (WPT) extension were used to assess the trial reporting quality (TRQ) and WPT-specific reporting quality (WRQ) of included SMTs, respectively. A binary score (0 or 1) was given to each item of the guidelines, and total scores were calculated for TRQ (score range, 0-32) and WRQ (score range, 0-15). Univariable and multivariable linear regression analyses were performed to identify factors associated with TRQ and WRQ.

RESULTS

A total of 42 SMTs were included. The mean overall scores for TRQ and WRQ were 16.8 [standard deviation (SD) 7.1] and 5.6 (SD 2.3), respectively. Only 11 SMTs (26.2%) presented the rationale for using a split-mouth design. Key methodological items including random sequence generation (22/42, 52.4%), allocation concealment (9/42, 21.4%), and blinding (20/42, 47.6%) were poorly reported. Only six SMTs (14.3%) used a paired method for sample size calculation, and half (21/42, 50.0%) considered the dependent nature of data in statistical analysis. In multivariable analyses, higher TRQ and WRQ were both significantly associated with journal, reported use of CONSORT and funding status.

CONCLUSIONS

The reporting quality of SMTs in orthodontics has much room for improvement. Joint efforts from relevant stakeholders are needed to improve the reporting quality of SMTs and reduce relevant avoidable research waste.

Are results from randomized trials in anesthesiology robust or fragile? An analysis using the fragility index

AIM

In anesthesiology, the findings from randomized controlled trials often underpin guidelines influencing clinical decision-making and therefore directly affect patient care. The aim of this study is to evaluate the fragility index and fragility quotient of randomized controlled trials published in the eight highest ranked anesthesiology journals. In addition, we assess the extent to which risk of bias scores, loss to follow-up, Web of Science Citation Index, and journal impact factor influence fragility index and fragility quotient.

METHODS

We included randomized trials published between 2014 and 2016 from the eight highest ranking anesthesiology journals based on Clarivate Analytics' Science Citation Index and Google Scholar Metrics: Anesthesiology subcategory. We included journals that published general anesthesia topics and omitted specialty anesthesia journals. The fragility index and fragility quotient for all included trials were calculated. Risk of bias for each trial was evaluated using the Cochrane 'risk of bias' Tool 2.0.

RESULTS

One hundred and thirty one randomized control trials were included in this analysis. The median fragility index was 3 (interquartile range 1.0-5.5) with a fragility quotient of 0.03 (interquartile range 0.01-0.08). In 11% (14/131) of trials, the number of patients lost to follow-up was greater than the corresponding fragility index. Weak correlations were found between fragility index and total sample size (r = 0.13) and between fragility index and event frequency (r = 0.19). A near-negligible correlation was found between 5-year impact factor and fragility index (r = -0.03) and, similarly, between fragility index and Science Citation Index (r = -0.05). Ten trials were at high risk of bias with the randomization process found to be the domain at the highest risk of bias.

CONCLUSION

In assessing the fragility of randomized controlled trials published in the top eight anesthesiology journals, our study suggests that statistically significant results in these journals are disconcertingly fragile. The median fragility index calculated from our 131 primary studies reveals that only three nonevents must be replaced with events to negate statistical significance. Although a current scale does not exist for fragility index ranges, many trials published by the top journals in anesthesiology are based on concerning methodology and highly fragile outcomes. With small median sample sizes and few patient events characterizing a large number of these trials, many of today's current guidelines and clinical practices may be founded on research containing statistical significance but lacking clinical significance.

Adequacy of risk of bias assessment in surgical vs non-surgical trials in Cochrane reviews: a methodological study

Background

Bias in randomized controlled trials (RCTs) can lead to underestimation or overestimation of the true effects of interventions. Surgical RCTs may suffer from the risk of bias (RoB) that is avoidable in trials of other interventions, and vice versa. We aimed to compare the adequacy of RoB assessments in surgical versus non-surgical RCTs included in Cochrane reviews and to assess the most common differences in those RoB assessments. Due to specificities of surgical trials, i.e. difficulties associated with blinding of surgical interventions, we hypothesized that assessments of surgical trials may be more adequate, compared to RCTs of non-surgical interventions.

Methods

This was a methodological study, analyzing methods of published Cochrane systematic reviews. Data were extracted from RoB tables in Cochrane reviews (judgments and accompanying explanatory comment) for the following four RoB domains used in the 2011 Cochrane RoB tool: randomization, allocation concealment, blinding of participants and personnel, and blinding of outcome assessors. We defined adequate assessments as those that were in line with instructions from the Cochrane Handbook for Systematic Reviews of Interventions. The prevalence of adequate assessments was compared in surgical versus non-surgical trials. The most common differences in both groups of reviews were presented.

Results

In 729 analyzed Cochrane reviews, there were 10,537 included trials. The prevalence of adequate RoB judgments made by Cochrane authors ranged from 87.9, 95%CI (87.3 to 88.6%) for randomization to 70.7, 95%CI (69.8 to 71.5%) for blinding of participants and personnel. For all analyzed RoB domains, the prevalence of adequate RoB domains was higher in surgical trials than in non-surgical trials. For two RoB domains assessing blinding, this difference between surgical and non-surgical trials was statistically significant (P < 0.001), while the difference was not significant for the RoB domain regarding randomization (P = 0.124) and allocation concealment (P = 0.039, β < 0.8).

Conclusions

RoB judgments were more in line with instructions from the Cochrane Handbook when Cochrane reviews assessed surgical trials, compared to those that analyzed non-surgical interventions. However, further steps are warranted to scrutinize RoB assessment in trials of both surgical and non-surgical interventions.

Particulate Production and Composite Dust during Routine Dental Procedures. A Systematic Review with Meta-Analyses

Composite dust generation is most likely a continuous and daily procedure in dental practice settings. The aim of this systematic review was to identify, compile and evaluate existing evidence on interventions and composite material properties related to the production of aerosolized dust during routine dental procedures. Seven electronic databases were searched, with no limits, supplemented by a manual search, on 27 April 2020 for published and unpublished research. Eligibility criteria comprised of studies of any design, describing composite dust production related to the implementation of any procedure in dental practice. Study selection, data extraction and risk of bias (RoB) assessment was undertaken independently either in duplicate, or confirmed by a second reviewer. Random effects meta-analyses of standardized mean differences (SMD) with associated 95% confidence intervals (CIs) were employed where applicable. A total of 375 articles were initially identified, resulting in 13 articles being included in the qualitative synthesis, of which 5 contributed to meta-analyses overall. Risk of bias recordings ranged between low and high, pertaining to unclear/raising some concerns, in most cases. All types of composites, irrespective of the filler particles, released significant amounts of nano-sized particles after being ground, with potentially disruptive respiratory effects. Evidence supported increased % distribution of particles < 100 nm for nanocomposite Filtek Supreme XTE compared to both conventional hybrid Z100MP (SMD: 1.96, 95% CI: 0.85, 3.07; p-value; 0.001) and nano- hybrid Tetric EvoCeram (SMD: 1.62, 95% CI: 0.56, 2.68; p-value: 0.003). For cytotoxicity considerations of generated aerosolized particles, both nanocomposites Filtek Supreme XTE and nanohybrid GradiO revealed negative effects on bronchial epithelial cell viability, as represented by % formazan reduction at 330-400 μg/ml for 24 hours, with no recorded differences between them (SMD: 0.19; 95% CI: -0.17, 0.55; p-value: 0.30). Effective and more rigorous management of dental procedures potentially liable to the generation of considerable amounts of aerosolized composite dust should be prioritized in contemporary dental practice. In essence, protective measures for the clinician and the practices' personnel should also be systematically promoted and additional interventions may be considered in view of the existing evidence.

Safety Considerations for Thermoplastic-Type Appliances Used as Orthodontic Aligners or Retainers. A Systematic Review and Meta-Analysis of Clinical and In-Vitro Research

Use of thermoplastic material in orthodontics, either as aligner or as retainer appliances, is common practice and is likely to increase in the years to come. However, no systematic assessment on safety considerations of these adjuncts has been implemented up to date. The aim of this systematic review was to collectively appraise the existing evidence from both clinical and laboratory studies, on whether these appliances are associated with any estrogenic/cytotoxic effects or bisphenol-A (BPA) and monomer leaching. Eight electronic databases were searched with no limits in December 22, 2019, for published and unpublished research. Eligibility criteria comprised of studies of any design, describing use of any type of thermoplastic aligner. Study selection, data extraction and risk of bias (RoB) assessment was done independently, either in duplicate or confirmed by a second reviewer. Random effects meta-analyses of weighted mean differences (WMD) with associated 95% Confidence Intervals (CIs) were planned. Quality of the evidence was evaluated with Grading of Recommendations Assessment, Development and Evaluation (GRADE). A total of 58 articles were initially identified, while 5 were included in qualitative synthesis and 2 of those contributed to the quantitative syntheses. Four studies were in-vitro, while one was a randomized controlled trial; all assessed some type of orthodontic aligner or retainer, either as-received or retrieved. Risk of bias recordings ranged between unclear and high for all studies. Proliferation induction capacity of thermoplastic appliances’ eluents on MCF-7 cells failed to be confirmed compared to beta-estradiol (2 studies: 5% v/v, WMD: −182.08; 95% CI: −198.83, −165.33; p-value < 0.001; and 20% v/v, WMD: −184.53; 95% CI: −206.17, −162.88; p-value < 0.001). No cytotoxic activity was detected as well. In addition, although evidence from in-vitro studies was indicative of no traceable detection of BPA or other monomers, the findings from a single clinical trial were allied to increased levels of BPA in whole stimulated saliva, after up to 30 days of thermoplastic retainer usage, compared to standard Hawley retainer. The quality of the evidence overall was low to medium. Current data from in-vitro research are indicative of an absence of an estrogenic or cytotoxic effect of thermoplastic aligners or retainers. Regarding BPA or monomer release, evidence from clinical and laboratory studies appear inconsistent.

A priori power considerations in orthodontic research: a 3 year meta-epidemiologic study

Aim

To assess the prevalence of a priori power calculations in orthodontic literature and to identify potential associations with a number of study characteristics, including journal, year of publication and statistical significance of the outcome.

Materials and methods

The electronic archives of four leading orthodontic journals with the highest impact factor (American Journal of Orthodontics and Dentofacial Orthopedics, AJODO; European Journal of Orthodontics, EJO; Angle Orthodontist, ANGLE; Orthodontics and Craniofacial Research, OCR) were assessed over a 3 year period until December 2018. The proportion of articles reporting a priori power calculations were recorded, and the association with journal, year of publication, study design, continent of authorship, number of centres and researchers, statistical significance of results and reporting of confidence intervals (CIs) was assessed. Univariable and multivariable regression were used to identify significant predictors.

Results

Overall, 654 eligible articles were retrieved, with the majority published in the AJODO (n = 246, 37.6%), followed by ANGLE (n = 222, 33.9%) and EJO (n = 139, 21.3%). A total of 233 studies (35.6%) presented power considerations a priori along with sample size calculations. Study design was a very strong predictor with interventional design presenting 3.02 times higher odds for a priori power assumptions compared to observational research [odds ratio (OR): 3.02; 95% CIs: 2.06, 4.42; P &lt; 0.001].

Conclusions

Presentation of a priori power considerations for sample size calculations was not universal in contemporary orthodontic literature, while specific study designs such as observational or animal and in vitro studies were less likely to report such considerations.

Publication pattern, study design, authors and countries involved in orthodontic RCTs - a bibliometric MEDLINE survey over the past 50 years

OBJECTIVES

The objective of this study was to investigate the number and proportions, study design, journal publications, authors and countries involved in orthodontic randomised controlled trials (RCTs) over the past 50 years.

METHOD

A MEDLINE database search (Entrez PubMed, http://www.ncbi.nlm.nih.gov ) was performed in November 2018 for RCT publications from 1 January 1968 to 31 December 2017. All orthodontic publications, clinical trials (CTs) or RCTs were selected. For each year from 1968 to 2017, the total number of orthodontic publications and total number of CTs and RCTs were computed. Following this, study design, journal publications, authors and countries involved in orthodontic RCTs were noted.

RESULTS

The RCTs accounted for 0.1% of all orthodontic publications in the 1970s and 1980s, and, following this, the proportion of RCTs was increased and amounted to 2.7% over the past decade (2008-2017). The majority of RCTs were of single centre design (93.4%) and in 88.3% a parallel-arm design was performed. The United States and United Kingdom endorsed 16.9% and 15.5% of the RCTs, followed by Turkey (11.1%), Brazil (7.0%), Sweden (6.6%), China (5.6%), Italy (5.4%), and Germany (4.1%). Of all RCTs, 74.2% were published in 20 orthodontic journals and 25.8% in 81 non-orthodontic journals. The American Journal of Orthodontics and Dentofacial Orthopedics, Angle Orthodontist, European Journal of Orthodontics and Journal of Orthodontics contributed to 60.2% of all the RCTs.

CONCLUSION

The considerable increase in orthodontic RCTs over the past 50 years implies an increased scientific impact of orthodontic literature.

Increasing the Value of Orthodontic Research Through the Use of Dental Patient-Reported Outcomes

Ten years ago, Chalmers and Glasziou pointed out in the Lancet that 85% of all biomedical research was being avoidably wasted because of imbalanced research question/outcome selection, as well as poor study design, execution, and reporting. According to findings of recent "research on research" studies, a high level of such kind of avoidable waste should also exist in orthodontic research. This warrants efforts to improve each stage of the research production and reporting process. Nowadays, patients' psychosocial function is considered a core element of oral health. Also, their treatment needs and preferences have formed a main component of evidence-based dentistry. Therefore, to achieve shared decision-making, orthodontists need to have an adequate understanding of each patient's values and perceptions. In this context, orthodontic research should be patient-centered so that the knowledge and perception gaps between clinicians and patients can be reduced, and research evidence that is suitable for patients to understand can be provided. In addition, patient-centered outcomes that can reflect patients' perceptions and psychosocial status should be widely used. However, recent scoping reviews have shown that during the past decade, patient-centered outcomes including those regarding adverse effects, health service resource utilization, and quality of life have remained under-represented in orthodontic trials. Thus, the use of dental patient-reported outcomes and dental patient-reported outcome measures should be promoted to facilitate the provision of a patient-centered evidence base, reduce the avoidable waste related to research question/outcome selection, and thereby increase the value of orthodontic research.

Evidence-based orthodontics: Too many systematic reviews, too few trials

Why are there so many systematic reviews in orthodontics, and what are the negative consequences of this for our speciality as an academic discipline?

Methodological review: quality of randomized controlled trials in health literacy

BACKGROUND

The growing move towards patient-centred care has led to substantial research into improving the health literacy skills of patients and members of the public. Hence, there is a pressing need to assess the methodology used in contemporary randomized controlled trials (RCTs) of interventions directed at health literacy, in particular the quality (risk of bias), and the types of outcomes reported.

METHODS

We conducted a systematic database search for RCTs involving interventions directed at health literacy in adults, published from 2009 to 2014. The Cochrane Risk of Bias tool was used to assess quality of RCT implementation. We also checked the sample size calculation for primary outcomes. Reported evidence of efficacy (statistical significance) was extracted for intervention outcomes in any of three domains of effect: knowledge, behaviour, health status. Demographics of intervention participants were also extracted, including socioeconomic status.

RESULTS

We found areas of methodological strength (good randomization and allocation concealment), but areas of weakness regarding blinding of participants, people delivering the intervention and outcomes assessors. Substantial attrition (losses by monitoring time point) was seen in a third of RCTs, potentially leading to insufficient power to obtain precise estimates of intervention effect on primary outcomes. Most RCTs showed that the health literacy interventions had some beneficial effect on knowledge outcomes, but this was typically for less than 3 months after intervention end. There were far fewer reports of significant improvements in substantive patient-oriented outcomes, such as beneficial effects on behavioural change or health (clinical) status. Most RCTs featured participants from vulnerable populations.

CONCLUSIONS

Our evaluation shows that health literacy trial design, conduct and reporting could be considerably improved, particularly by reducing attrition and obtaining longer follow-up. More meaningful RCTs would also result if health literacy trials were designed with public and patient involvement to focus on clinically important patient-oriented outcomes, rather than just knowledge, behaviour or skills in isolation.