Bias and small-study effects influence treatment effect estimates: a meta-epidemiological study in oral medicine

Rapid review: A review of methods and recommendations based on current evidence

Rapid review (RR) could accelerate the traditional systematic review (SR) process by simplifying or omitting steps using various shortcuts. With the increasing popularity of RR, numerous shortcuts had emerged, but there was no consensus on how to choose the most appropriate ones. This study conducted a literature search in PubMed from inception to December 21, 2023, using terms such as "rapid review" "rapid assessment" "rapid systematic review" and "rapid evaluation". We also scanned the reference lists and performed citation tracking of included impact studies to obtain more included studies. We conducted a narrative synthesis of all RR approaches, shortcuts and studies assessing their effectiveness at each stage of RRs. Based on the current evidence, we provided recommendations on utilizing certain shortcuts in RRs. Ultimately, we identified 185 studies focusing on summarizing RR approaches and shortcuts, or evaluating their impact. There was relatively sufficient evidence to support the use of the following shortcuts in RRs: limiting studies to those published in English-language; conducting abbreviated database searches (e.g., only searching PubMed/MEDLINE, Embase, and CENTRAL); omitting retrieval of grey literature; restricting the search timeframe to the recent 20 years for medical intervention and the recent 15 years for reviewing diagnostic test accuracy; conducting a single screening by an experienced screener. To some extent, the above shortcuts were also applicable to SRs. This study provided a reference for future RR researchers in selecting shortcuts, and it also presented a potential research topic for methodologists.

Trial characteristics and treatment effect estimates in randomized controlled trials of Chinese herbal medicine: A meta-epidemiological study

BACKGROUND

Previously published meta-epidemiological studies focused on Western medicine have identified some trial characteristics that impact the treatment effect of randomized controlled trials (RCTs). Nevertheless, it remains unclear if similar associations exist in RCTs on Chinese herbal medicine (CHM). Further, Chinese medicine-related characteristics have not been explored yet.

OBJECTIVE

To investigate trial characteristics related to treatment effect estimates on CHM RCTs.

SEARCH STRATEGY

This meta-epidemiological study searched 5 databases for systematic reviews on CHM treatment published between January 2011 and July 2021.

INCLUSION CRITERIA

An eligible systematic review should only include RCTs of CHM and conduct at least one meta-analysis.

DATA EXTRACTION AND ANALYSIS

Two reviewers independently conducted data extraction on general characteristics of systematic reviews, meta-analyses and included RCTs. They also assessed the risk of bias of RCTs using the Cochrane risk of bias tool. A two-step approach was used for data analyses. The ratio of odds ratios (ROR) and difference in standardized mean differences (dSMD) with 95% confidence interval (CI) were applied to present the difference in effect estimates for binary and continuous outcomes, respectively.

RESULTS

Ninety-one systematic reviews, comprising 1338 RCTs were identified. For binary outcomes, RCTs incorporated with syndrome differentiation (ROR: 1.23; 95 % CI: [1.07, 1.39]), adopting Chinese medicine formula (ROR: 1.19; 95% CI: [1.03, 1.34]), with low risk of bias on incomplete outcome data (ROR: 1.29; 95% CI: [1.06, 1.52]) and selective outcome reporting (ROR: 1.12; 95% CI: [1.01, 1.24]), as well as a trial size ≥ 100 (ROR: 1.23; 95% CI: [1.04, 1.42]) preferred to show larger effect estimates. As for continuous outcomes, RCTs with Chinese medicine diagnostic criteria (dSMD: 0.23; 95% CI: [0.06, 0.41]), judged as high/unclear risk of bias on allocation concealment (dSMD: -0.70; 95% CI: [-0.99, -0.42]), with low risk of bias on incomplete outcome data (dSMD: 0.30; 95% CI: [0.18, 0.43]), conducted at a single center (dSMD: -0.33; 95% CI: [-0.61, -0.05]), not using intention-to-treat analysis (dSMD: -0.75; 95% CI: [-1.43, -0.07]), and without funding support (dSMD: -0.22; 95% CI: [-0.41, -0.02]) tended to show larger effect estimates.

CONCLUSION

This study provides empirical evidence for the development of a specific critical appraisal tool for risk of bias assessments on CHM RCTs. Please cite this article as: Wang BH, Lin YL, Gao YY, Song JL, Qin L, Li LQ, Liu WQ, Zhong CCW, Jiang MY, Mao C, Yang XB, Chung VCH, Wu IXY. Trial characteristics and treatment effect estimates in randomized controlled trials of Chinese herbal medicine: A meta-epidemiological study. J Integr Med. 2024; 22(3): 223-234.

Recruitment rates and strategies in exercise trials in cancer survivorship: a systematic review

PURPOSE

Despite clear evidence-based supporting a benefit to exercise on physical and psychological metrics in patients with cancer, recruitment to exercise trials amongst cancer survivors is suboptimal. We explore current recruitment rates, strategies, and common barriers to participation in exercise oncology trials in cancer survivorship.

METHODS

A systematic review was conducted using a pre-defined search strategy in EMBASE, CINAHL, Medline, Cochrane Library, and Web of Science. The search was performed up to 28/02/2022. Screening of titles and abstracts, full-text review, and data extraction was completed in duplicate.

RESULTS

Of the 3204 identified studies, 87 papers corresponding to 86 trials were included. Recruitment rates were highly variable with a median rate of 38% (range 0.52-100%). Trials recruiting prostate cancer patients only had the highest median recruitment rate (45.9%) vs trials recruiting colorectal cancer patients only which had the lowest (31.25%). Active recruitment strategies such as direct recruitment via a healthcare professional were associated with higher recruitment rates (rho = 0.201, p = 0.064). Common reasons for non-participation included lack of interest (46.51%, n (number of studies) = 40); distance and transport (45.3%, n = 39); and failure to contact (44.2%, n = 38).

CONCLUSIONS

Recruitment of cancer survivors to exercise interventions is suboptimal with barriers being predominantly patient-oriented. This paper provides the benchmark for current recruitment rates to exercise oncology trials, providing data for trialists planning future trial design and implementation, optimise future recruitment strategies, and evaluate their own recruitment success against current practice.

IMPLICATIONS FOR CANCER SURVIVORS

Enhanced recruitment to cancer survivorship exercise trials is necessary in facilitating the publication of definitive exercise guidelines, generalisable to varying cancer cohorts.

PROSPERO REGISTRATION NUMBER

CRD42020185968.

Global prevalence of social isolation among community-dwelling older adults: A systematic review and meta-analysis

BACKGROUND

While the world's population ages, social isolation has continued to increase globally. However, no review exists on the prevalence of social isolation among community-dwelling older adults, and the global prevalence remains uncertain. This study aims to estimate the global prevalence of social isolation among community-dwelling older adults and to identify potential covariates including study characteristics (methodological diversity) or populations (clinical diversity) that contribute to the heterogeneity.

METHODS

This review searched through seven search engines and databases. The meta-analysis was conducted using the metafor package in the R software. The random-effects model was used to calculate the prevalence rates. Cochran's Q statistics and I² statistics were used to assess the statistical heterogeneity of prevalence estimates. Studies were appraised using the Newcastle-Ottawa Scale and the Grading of Recommendations, Assessment, Development, and Evaluations criteria for the quality of individual articles and the certainty of the evidence, respectively.

RESULTS

A total of 41 studies were selected from databases and reference lists. The pooled prevalence rate was 25% (95% CI: 21.0-30.0). The sample size was found to be a significant covariate of the prevalence estimate in the subgroup analysis.

CONCLUSIONS

We found 13 high-quality studies, but the overall quality of evidence very low. This study provides the prevalence of social isolation in community-dwelling older adults, identifying vulnerable groups for targeted intervention. Well-designed observational research with standard measures is recommended for future studies.

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).

Extension of the Composite Quality Score (CQS) as an appraisal tool for prospective, controlled clinical therapy trials-A systematic review of meta-epidemiological evidence

AIM

To conduct a survey of current meta-epidemiological studies to identify additional trial design characteristics that may be associated with significant over- or underestimation of the treatment effect and to use such identified characteristics as a basis for the formulation of new CQS appraisal criteria.

MATERIALS AND METHODS

We retrieved eligible studies from two systematic reviews on this topic (latest search May 2015) and searched the databases PubMed and Embase for further studies from June 2015 -March 2022. All data were extracted by one author and verified by another. Sufficiently homogeneous estimates from single studies were pooled using random-effects meta-analysis. Trial design characteristics associated with statistically significant estimates from single datasets (which could not be pooled) and meta-analyses were used as a basis to formulate new or amend existing CQS criteria.

RESULTS

A total of 38 meta-epidemiological studies were identified. From these, seven trial design characteristics associated with statistically significant over- or underestimation of the true therapeutic effect were found.

CONCLUSION

One new criterion concerning double-blinding was added to the CQS, and the original criteria for concealing the random allocation sequence and for minimum sample size were amended.

Does vaginal progesterone prevent recurrent preterm birth in women with a singleton gestation and a history of spontaneous preterm birth? Evidence from a systematic review and meta-analysis

OBJECTIVE

To assess the efficacy and safety of vaginal progesterone to prevent recurrent preterm birth and adverse perinatal outcomes in singleton gestations with a history of spontaneous preterm birth.

DATA SOURCES

MEDLINE, Embase, LILACS, and CINAHL (from their inception to February 28, 2022), Cochrane databases, Google Scholar, bibliographies, and conference proceedings.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials that compared vaginal progesterone to placebo or no treatment in asymptomatic women with a singleton gestation and a history of spontaneous preterm birth.

METHODS

The primary outcomes were preterm birth <37 and <34 weeks of gestation. The secondary outcomes included adverse maternal and perinatal outcomes. Pooled relative risks with 95% confidence intervals were calculated. We assessed the risk of bias in the included studies, heterogeneity (I2 test), small-study effects, publication bias, and quality of evidence; performed subgroup and sensitivity analyses; and calculated 95% prediction intervals and adjusted relative risks.

RESULTS

Ten studies (2958 women) met the inclusion criteria: 7 with a sample size <150 (small studies) and 3 with a sample size >600 (large studies). Among the 7 small studies, 4 were at high risk of bias, 2 were at some concerns of bias, and only 1 was at low risk of bias. All the large studies were at low risk of bias. Vaginal progesterone significantly decreased the risk of preterm birth <37 weeks (relative risk, 0.64; 95% confidence interval, 0.50-0.81; I2=75%; 95% prediction interval, 0.31-1.32; very low-quality evidence) and <34 weeks (relative risk, 0.62; 95% confidence interval, 0.42-0.92; I2=66%; 95% prediction interval, 0.23-1.68; very low-quality evidence), and the risk of admission to the neonatal intensive care unit (relative risk, 0.53; 95% confidence interval, 0.33-0.85; I2=67%; 95% prediction interval, 0.16-1.79; low-quality evidence). There were no significant differences between the vaginal progesterone and the placebo or no treatment groups in other adverse perinatal and maternal outcomes. Subgroup analyses revealed that vaginal progesterone decreased the risk of preterm birth <37 weeks (relative risk, 0.43; 95% confidence interval, 0.33-0.55; I2=0%) and <34 weeks (relative risk, 0.27; 95% confidence interval, 0.15-0.49; I2=0%) in the small but not in the large studies (relative risk, 0.98; 95% confidence interval, 0.88-1.09; I2=0% for preterm birth <37 weeks; and relative risk, 0.94; 95% confidence interval, 0.78-1.13; I2=0% for preterm birth <34 weeks). Sensitivity analyses restricted to studies at low risk of bias indicated that vaginal progesterone did not reduce the risk of preterm birth <37 weeks (relative risk, 0.96; 95% confidence interval, 0.84-1.09) and <34 weeks (relative risk, 0.90; 95% confidence interval, 0.71-1.15). There was clear evidence of substantial small-study effects in the meta-analyses of preterm birth <37 and <34 weeks of gestation because of funnel plot asymmetry and the marked differences in the pooled relative risks obtained from fixed-effect and random-effects models. The adjustment for small-study effects resulted in a markedly reduced and nonsignificant effect of vaginal progesterone on preterm birth <37 weeks (relative risk, 0.86; 95% confidence interval, 0.68-1.10) and <34 weeks (relative risk, 0.92; 95% confidence interval, 0.60-1.42).

CONCLUSION

There is no convincing evidence supporting the use of vaginal progesterone to prevent recurrent preterm birth or to improve perinatal outcomes in singleton gestations with a history of spontaneous preterm birth.

Trial-level characteristics associate with treatment effect estimates: a systematic review of meta-epidemiological studies

BACKGROUND

To summarize the up-to-date empirical evidence on trial-level characteristics of randomized controlled trials associated with treatment effect estimates.

METHODS

A systematic review searched three databases up to August 2020. Meta-epidemiological (ME) studies of randomized controlled trials on intervention effect were eligible. We assessed the methodological quality of ME studies using a self-developed criterion. Associations between treatment effect estimates and trial-level characteristics were presented using forest plots.

RESULTS

Eighty ME studies were included, with 25/80 (31%) being published after 2015. Less than one-third ME studies critically appraised the included studies (26/80, 33%), published a protocol (23/80, 29%), and provided a list of excluded studies with justifications (12/80, 15%). Trials with high or unclear (versus low) risk of bias on sequence generation (3/14 for binary outcome and 1/6 for continuous outcome), allocation concealment (11/18 and 1/6), double blinding (5/15 and 2/4) and smaller sample size (4/5 and 2/2) significantly associated with larger treatment effect estimates. Associations between high or unclear risk of bias on allocation concealment (5/6 for binary outcome and 1/3 for continuous outcome), double blinding (4/5 and 1/3) and larger treatment effect estimates were more frequently observed for subjective outcomes. The associations between treatment effect estimates and non-blinding of outcome assessors were removed in trials using multiple observers to reach consensus for both binary and continuous outcomes. Some trial characteristics in the Cochrane risk-of-bias (RoB2) tool have not been covered by the included ME studies, including using validated method for outcome measures and selection of the reported results from multiple outcome measures or multiple analysis based on results (e.g., significance of the results).

CONCLUSIONS

Consistently significant associations between larger treatment effect estimates and high or unclear risk of bias on sequence generation, allocation concealment, double blinding and smaller sample size were found. The impact of allocation concealment and double blinding were more consistent for subjective outcomes. The methodological and reporting quality of included ME studies were dissatisfactory. Future ME studies should follow the corresponding reporting guideline. Specific guidelines for conducting and critically appraising ME studies are needed.

Absence of small study effects in neurosurgical meta-analyses: A meta-epidemiological study

BACKGROUND

Small studies are prone to lower methodological quality and publication bias, and are more likely to report greater beneficial effects. A meta-epidemiological study was undertaken to investigate and quantify the impact of small study effects on meta-analyses in the neurosurgical literature.

METHODS

A PubMed search was used to procure meta-analyses from Journal of Neurosurgery, Neurosurgery, Spine, Acta Neurochirurgica and Journal of Neurotrauma. Outcome data were extracted from meta-analyses the effect of study size was estimated by calculating the ratio of odds ratios (RORs) between small and large studies.

RESULTS

16 meta-analyses of 229 primary studies and 90,629 patients were included. All but two included pooled outcomes were significantly different from 1. On average small studies did not demonstrate greater beneficial effects, with an estimated pooled ROR of 1.32 (95% CI, 0.89 to 1.75). Stratification by meta-analysis effect size and heterogeneity yielded similar findings.

CONCLUSIONS

The absence of small study effects in meta-analyses of neurosurgical studies may reflect widespread poor quality of the neurosurgical literature affecting both large and small studies, rather than an absence of publication bias.

Altmetrics Attention Scores for Randomized Controlled Trials in Total Joint Arthroplasty Are Reflective of High Scientific Quality: An Altmetrics-Based Methodological Quality and Bias Analysis

The Altmetric Attention Score (AAS) has been associated with citation rates across medical and surgical disciplines. However, factors that drive high AAS remain poorly understood and there remains multiple pitfalls to correlating these metrics alone with the quality of a study. The purpose of the current study was to determine the relationship between methodologic and study biases and the AAS in randomized controlled trials (RCTs) published in total joint arthroplasty journals.

Registered trials report less beneficial treatment effects than unregistered ones: a meta-epidemiological study in orthodontics

OBJECTIVES

Clinical trial registration is widely recommended because it allows tracking of trials that helps ensure full and unbiased reporting of their results. The aim of the present overview was to provide empirical evidence on bias associated with trial registration via a meta-epidemiological approach.

STUDY DESIGN AND SETTINGS

Six databases were searched in September 2017 for randomized clinical trials and systematic reviews thereof assessing the effects of orthodontic clinical interventions. After duplicate study selection and data extraction, statistical analysis included a two-step meta-epidemiological approach within- and across-included meta-analyses with a Paule-Mandel random-effects model to calculate differences in standardized mean differences (ΔSMD) between registered and unregistered trials and their 95% confidence intervals (CI), followed by subgroup and sensitivity analyses.

RESULTS

A total of 16 meta-analyses with 83 trials and 4,988 patients collectively were finally included, which indicated that registered trials reported less beneficial treatment effects than unregistered trials (ΔSMD = -0.36; 95% CI = -0.60, -0.12). Although some small-study effects were identified, sensitivity analyses according to precision and risk of bias indicated robustness.

CONCLUSION

Signs of bias from lack of trial protocol registration were found with nonregistered trials reporting more beneficial intervention effects than registered ones. Caution is warranted by the interpretation of nonregistered randomized trials or systematic reviews thereof.

Influence of piezotomy and osteoperforation of the alveolar process on the rate of orthodontic tooth movement: a systematic review

OBJECTIVE

The minimally invasive procedures piezosurgical corticocision and osteoperforation have been advocated as methods to accelerate orthodontic tooth movement and to shorten treatment time, but without large-scale trauma of the periosteum and the bone. The aim of this study was to evaluate if there is evidence supporting these claims based on a systematic review of the literature.

MATERIALS AND METHODS

A search of PubMed and Google Scholar with the combined search terms "piezo*" and "tooth movement" was performed until May 2016. In addition, the keywords "osteoperforation" and "piezopuncture" were searched in both databases. All scientific articles were considered and examined for suitability by two scientists. Disagreements resolved by consensus. The first inclusion criterion was studies with human species. Second inclusion criterion the surgical procedure had to be performed transmucosally and without the elevation of a mucoperiosteal flap. Case series were also considered.

RESULTS

The Google Scholar search delivered 516, the PubMed search 60 references. A total of 36 human trials fulfilling the first inclusion criterion were identified. Among those, in only 13 publications was a transmucosal technique used (12 on piezosurgical corticocision and 1 on osteoperforation). Of the 13 articles, 9 represented case series and only 4 were clinical trials. In all four trials, an acceleration of the orthodontic treatment was reported. However, the extent of the acceleration was inconsistent and in one article it disappeared when assessing the overall orthodontic treatment.

CONCLUSION

Evidence for an acceleration of tooth movement in conjunction with the minimally invasive methods piezosurgical corticocision and osteoperforation of the alveolar process in humans is low.

Laboratory mechanical parameters of composite resins and their relation to fractures and wear in clinical trials-A systematic review

OBJECTIVE

To evaluate a range of mechanical parameters of composite resins and compare the data to the frequency of fractures and wear in clinical studies.

METHODS

Based on a search of PubMed and SCOPUS, clinical studies on posterior composite restorations were investigated with regard to bias by two independent reviewers using Cochrane Collaboration's tool for assessing risk of bias in randomized trials. The target variables were chipping and/or fracture, loss of anatomical form (wear) and a combination of both (summary clinical index). These outcomes were modelled by time and material in a linear mixed effect model including random study and experiment effects. The laboratory data from one test institute were used: flexural strength, flexural modulus, compressive strength, and fracture toughness (all after 24-h storage in distilled water). For some materials flexural strength data after aging in water/saliva/ethanol were available. Besides calculating correlations between clinical and laboratory outcomes, we explored whether a model including a laboratory predictor dichotomized at a cut-off value better predicted a clinical outcome than a linear model.

RESULTS

A total of 74 clinical experiments from 45 studies were included involving 31 materials for which laboratory data were also available. A weak positive correlation between fracture toughness and clinical fractures was found (Spearman rho=0.34, p=0.11) in addition to a moderate and statistically significant correlation between flexural strength and clinical wear (Spearman rho=0.46, p=0.01). When excluding those studies with "high" risk of bias (n=18), the correlations were generally weaker with no statistically significant correlation. For aging in ethanol, a very strong correlation was found between flexural strength decrease and clinical index, but this finding was based on only 7 materials (Spearman rho=0.96, p=0.0001). Prediction was not consistently improved with cutoff values.

SIGNIFICANCE

Correlations between clinical and laboratory outcomes were moderately positive with few significant results, fracture toughness being correlated with clinical fractures and flexural strength with clinical wear. Whether artificial aging enhances the prognostic value needs further investigations.

Noninvasive Ventilation with Heliox for Respiratory Distress Syndrome in Preterm Infant: A Systematic Review and Meta-Analysis

Objectives. To assess whether noninvasive ventilation with Heliox reduces the need for endotracheal ventilation and subsequent complications in preterm infants with respiratory distress syndrome (RDS). Methods. A search of major electronic databases, including MEDLINE and the Cochrane Central Register of Controlled Trials, for randomized or quasi-randomized controlled trials that compared noninvasive ventilation with Heliox versus noninvasive ventilation with standard gas for preterm infants with RDS was performed. The primary outcome was the incidence of intubation. The secondary outcomes were the level of PaCO₂, the use of surfactant, and other complications. Results. Two randomized and one quasi-randomized controlled trials including 123 preterm infants were assessed. Heliox was found to significantly decrease the incidence of intubation (RR: 0.42; 95% CI: 0.23 to 0.78), the level of PaCO₂ (MD: −9.61; 95% CI: −15.76 to −03.45), and the use of surfactant (RR: 0.25; 95% CI: 0.10 to 0.61) as compared with standard gas. No significant differences were found in other secondary outcomes. Conclusions. Noninvasive ventilation with Heliox decreases the incidence of intubation in preterm infants suffering from RDS. However, data on clinical outcomes are limited. Larger trials are needed to verify the beneficial effects.

Evidence regarding lingual fixed orthodontic appliances' therapeutic and adverse effects is insufficient

Data sourcesMedline, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials, Virtual Health Library and Web of Science were systematically searched up to July 2015 without limitations. Scopus, Google Scholar, ClinicalTrials.gov, the ISRCTN registry as well as reference lists of the trials included and relevant reviews were manually searched.Study selectionRandomised (RCTs) and prospective non-randomised clinical trials (non-RCTs) on human patients that compared therapeutic and adverse effects of lingual and labial appliances were considered. One reviewer initially screened titles and subsequently two reviewers independently screened the selected abstracts and full texts.Data extraction and synthesisThe data were extracted independently by the reviewers. Missing or unclear information, ongoing trials and raw data from split-mouth trials were requested from the authors of the trials. The quality of the included trials and potential bias across studies were assessed using Cochrane's risk of bias tool and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. For parallel trials, mean difference (MD) and the relative risk (RR) were used for continuous (objective speech performance, subjective speech performance, intercanine width, intermolar width and sagittal anchorage loss) and binary outcomes (eating difficulty), respectively. The standardised mean difference (SMD) was chosen to pool, after conversion, the outcome (oral discomfort) that assessed both binary and continuous. Random-effects meta-analyses were conducted, followed by subgroup and sensitivity analyses.ResultsThirteen papers pertaining to 11 clinical trials (three parallel RCTs, one split-mouth RCT and seven parallel prospective non-RCTs) were included with a total of 407 (34% male/66% female) patients. All trials had at least one bias domain at high risk of bias. Compared with labial appliances, lingual appliances were associated with increased overall oral discomfort, increased speech impediment (measured using auditory analysis), worse speech performance assessed by laypersons, increased eating difficulty and decreased intermolar width. On the other hand, lingual appliances were associated with increased intercanine width and significantly decreased anchorage loss of the maxillary first molar during space closure. However, the quality of all analyses included was judged as very low because of the high risk of bias of the included trials, inconsistency and imprecision.ConclusionsBased on existing trials there is insufficient evidence to make robust recommendations for lingual fixed orthodontic appliances regarding their therapeutic or adverse effects, as the quality of evidence was low.

Meta-epidemiological study: a step-by-step approach by using R

The results of meta-analysis are usually influenced by characteristics of component trials. These characteristics include but are not limited to sample size, publication language, quality of study design and the number of participating centers. Because systematic review and meta-analysis is considered to be evidence of the highest quality in the era of evidence-based medicine, characteristics that may bias the results of meta-analysis should be fully investigated. Meta-epidemiological study aims to investigate the impact of study design characteristics on treatment effect. The article introduces how to perform meta-epidemiological study by using R software. There are several methodological approaches to perform meta-epidemiological study, depending on whether there is heterogeneity between meta-analyses and between trials. When there is no significant heterogeneity, these results would be similar.

Lingual vs. labial fixed orthodontic appliances: systematic review and meta-analysis of treatment effects

The aim of this systematic review was to compare the therapeutic and adverse effects of lingual and labial orthodontic fixed appliances from clinical trials on human patients in an evidence-based manner. Randomized and prospective non-randomized clinical trials comparing lingual and labial appliances were included. Risk of bias within and across studies was assessed using the Cochrane tool and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Random-effects meta-analyses were conducted, followed by subgroup and sensitivity analyses. Six electronic databases were searched from inception to July 2015, without limitations. A total of 13 papers pertaining to 11 clinical trials were included with a total of 407 (34% male/66% female) patients. Compared with labial appliances, lingual appliances were associated with increased overall oral discomfort, increased speech impediment (measured using auditory analysis), worse speech performance assessed by laypersons, increased eating difficulty, and decreased intermolar width. On the other hand, lingual appliances were associated with increased intercanine width and significantly decreased anchorage loss of the maxillary first molar during space closure. Based on existing trials, there is insufficient evidence to make robust recommendations for lingual fixed orthodontic appliances regarding their therapeutic or adverse effects, as the quality of evidence was low.

Deviation from intention to treat analysis in randomised trials and treatment effect estimates: meta-epidemiological study

OBJECTIVE

To examine whether deviation from the standard intention to treat analysis has an influence on treatment effect estimates of randomised trials.

DESIGN

Meta-epidemiological study.

DATA SOURCES

Medline, via PubMed, searched between 2006 and 2010; 43 systematic reviews of interventions and 310 randomised trials were included.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

From each year searched, random selection of 5% of intervention reviews with a meta-analysis that included at least one trial that deviated from the standard intention to treat approach. Basic characteristics of the systematic reviews and randomised trials were extracted. Information on the reporting of intention to treat analysis, outcome data, risk of bias items, post-randomisation exclusions, and funding were extracted from each trial. Trials were classified as: ITT (reporting the standard intention to treat approach), mITT (reporting a deviation from the standard approach), and no ITT (reporting no approach). Within each meta-analysis, treatment effects were compared between mITT and ITT trials, and between mITT and no ITT trials. The ratio of odds ratios was calculated (value <1 indicated larger treatment effects in mITT trials than in other trial categories).

RESULTS

50 meta-analyses and 322 comparisons of randomised trials (from 84 ITT trials, 118 mITT trials, and 108 no ITT trials; 12 trials contributed twice to the analysis) were examined. Compared with ITT trials, mITT trials showed a larger intervention effect (pooled ratio of odds ratios 0.83 (95% confidence interval 0.71 to 0.96), P=0.01; between meta-analyses variance τ(2)=0.13). Adjustments for sample size, type of centre, funding, items of risk of bias, post-randomisation exclusions, and variance of log odds ratio yielded consistent results (0.80 (0.69 to 0.94), P=0.005; τ(2)=0.08). After exclusion of five influential studies, results remained consistent (0.85 (0.75 to 0.98); τ(2)=0.08). The comparison between mITT trials and no ITT trials showed no statistical difference between the two groups (adjusted ratio of odds ratios 0.92 (0.70 to 1.23); τ(2)=0.57).

CONCLUSIONS

Trials that deviated from the intention to treat analysis showed larger intervention effects than trials that reported the standard approach. Where an intention to treat analysis is impossible to perform, authors should clearly report who is included in the analysis and attempt to perform multiple imputations.

Publication bias & small-study effects in pediatric dentistry meta-analyses

OBJECTIVES

The aim of this study was to examine the presence and extent of publication bias and small-study effects in meta-analyses (MAs) investigating pediatric dentistry-related subjects.

METHODS

Following a literature search, 46 MAs including 882 studies were analyzed qualitatively. Of these, 39 provided enough data to be re-analyzed. Publication bias was assessed with the following methods: contour-enhanced funnel plots, Begg and Mazumdar's rank correlation and Egger's linear regression tests, Rosenthal's failsafe N, and Duval and Tweedie's "trim and fill" procedure.

RESULTS

Only a few MAs adequately assessed the existence and effect of publication bias. Inspection of the funnel plots indicated asymmetry, which was confirmed by Begg-Mazumdar's test in 18% and by Egger's test in 33% of the MAs. According to Rosenthal's criterion, 80% of the MAs were robust, while adjusted effects with unpublished studies differed from little to great from the unadjusted ones. Pooling of the Egger's intercepts indicated that evidence of asymmetry was found in the pediatric dental literature, which was accentuated in dental journals and in diagnostic MAs. Since indications of small-study effects and publication bias in pediatric dentistry were found, the influence of small or missing trials on estimated treatment effects should be routinely assessed in future MAs.