Effect of hygiene interventions on acute respiratory infections in childcare, school and domestic settings in low- and middle-income countries: a systematic review

OBJECTIVES

Acute respiratory infections (ARIs) disproportionately affect those living in low- and middle-income countries (LMICs). We aimed to determine whether hygiene interventions delivered in childcare, school or domestic settings in LMICs effectively prevent or reduce ARIs.

METHODS

We registered our systematic review with PROSPERO (CRD42017058239) and searched MEDLINE, EMBASE, CENTRAL, and Scopus from inception to 17 October 2017 for randomised controlled trials (RCTs) examining the impact of hygiene interventions on ARI morbidity in adults and children in community-based settings in LMICs. We stratified data into childcare, school and domestic settings and used the Grading of Recommendations Assessment, Development and Evaluation approach to assess evidence quality.

RESULTS

We identified 14 cluster RCTs evaluating hand-hygiene interventions in LMICs with considerable heterogeneity in setting, size, intervention delivery and duration. We found reduced ARI-related absenteeism and illness in childcare settings (low- to moderate-quality evidence). In school settings, we found reduced ARI-related absenteeism and laboratory-confirmed influenza (moderate- to high-quality evidence), but no reduction in ARI illness (low-quality evidence). In domestic settings, we found reduced ARI illness and pneumonia amongst children in urban settlements (high-quality evidence) but not in rural settlements (low-quality evidence), and no effect on secondary transmission of influenza in households (moderate-quality evidence).

CONCLUSIONS

Evidence suggests that hand-hygiene interventions delivered in childcare, school and domestic settings can reduce ARI morbidity, but effectiveness varies according to setting, intervention target and intervention compliance. Further studies are needed to develop, deliver and evaluate targeted and sustainable hygiene interventions in LMICs.

Sample size calculations for cluster randomised crossover trials in Australian and New Zealand intensive care research

OBJECTIVE

The cluster randomised crossover (CRXO) design provides an opportunity to conduct randomised controlled trials to evaluate low risk interventions in the intensive care setting. Our aim is to provide a tutorial on how to perform a sample size calculation for a CRXO trial, focusing on the meaning of the elements required for the calculations, with application to intensive care trials.

DATA SOURCES

We use all-cause in-hospital mortality from the Australian and New Zealand Intensive Care Society Adult Patient Database clinical registry to illustrate the sample size calculations.

METHODS

We show sample size calculations for a two-intervention, two 12-month period, cross-sectional CRXO trial. We provide the formulae, and examples of their use, to determine the number of intensive care units required to detect a risk ratio (RR) with a designated level of power between two interventions for trials in which the elements required for sample size calculations remain constant across all ICUs (unstratified design); and in which there are distinct groups (strata) of ICUs that differ importantly in the elements required for sample size calculations (stratified design).

RESULTS

The CRXO design markedly reduces the sample size requirement compared with the parallel-group, cluster randomised design for the example cases. The stratified design further reduces the sample size requirement compared with the unstratified design.

CONCLUSIONS

The CRXO design enables the evaluation of routinely used interventions that can bring about small, but important, improvements in patient care in the intensive care setting.

Effectiveness of a new model of primary care management on knee pain and function in patients with knee osteoarthritis: Protocol for THE PARTNER STUDY

BACKGROUND

To increase the uptake of key clinical recommendations for non-surgical management of knee osteoarthritis (OA) and improve patient outcomes, we developed a new model of service delivery (PARTNER model) and an intervention to implement the model in the Australian primary care setting. We will evaluate the effectiveness and cost-effectiveness of this model compared to usual general practice care.

METHODS

We will conduct a mixed-methods study, including a two-arm, cluster randomised controlled trial, with quantitative, qualitative and economic evaluations. We will recruit 44 general practices and 572 patients with knee OA in urban and regional practices in Victoria and New South Wales. The interventions will target both general practitioners (GPs) and their patients at the practice level. Practices will be randomised at a 1:1 ratio. Patients will be recruited if they are aged ≥45 years and have experienced knee pain ≥4/10 on a numerical rating scale for more than three months. Outcomes are self-reported, patient-level validated measures with the primary outcomes being change in pain and function at 12 months. Secondary outcomes will be assessed at 6 and 12 months. The implementation intervention will support and provide education to intervention group GPs to deliver effective management for patients with knee OA using tailored online training and electronic medical record support. Participants with knee OA will have an initial GP visit to confirm their diagnosis and receive management according to GP intervention or control group allocation. As part of the intervention group GP management, participants with knee OA will be referred to a centralised multidisciplinary service: the PARTNER Care Support Team (CST). The CST will be trained in behaviour change support and evidence-based knee OA management. They will work with patients to develop a collaborative action plan focussed on key self-management behaviours, and communicate with the patients' GPs. Patients receiving care by intervention group GPs will receive tailored OA educational materials, a leg muscle strengthening program, and access to a weight-loss program as appropriate and agreed. GPs in the control group will receive no additional training and their patients will receive usual care.

DISCUSSION

This project aims to address a major evidence-to-practice gap in primary care management of OA by evaluating a new service delivery model implemented with an intervention targeting GP practice behaviours to improve the health of people with knee OA.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry: ACTRN12617001595303 , date of registration 1/12/2017.

Prevalence and reporting of recruitment, randomisation and treatment errors in clinical trials: A systematic review

Background/aims In clinical trials, it is not unusual for errors to occur during the process of recruiting, randomising and providing treatment to participants. For example, an ineligible participant may inadvertently be randomised, a participant may be randomised in the incorrect stratum, a participant may be randomised multiple times when only a single randomisation is permitted or the incorrect treatment may inadvertently be issued to a participant at randomisation. Such errors have the potential to introduce bias into treatment effect estimates and affect the validity of the trial, yet there is little motivation for researchers to report these errors and it is unclear how often they occur. The aim of this study is to assess the prevalence of recruitment, randomisation and treatment errors and review current approaches for reporting these errors in trials published in leading medical journals. Methods We conducted a systematic review of individually randomised, phase III, randomised controlled trials published in New England Journal of Medicine, Lancet, Journal of the American Medical Association, Annals of Internal Medicine and British Medical Journal from January to March 2015. The number and type of recruitment, randomisation and treatment errors that were reported and how they were handled were recorded. The corresponding authors were contacted for a random sample of trials included in the review and asked to provide details on unreported errors that occurred during their trial. Results We identified 241 potentially eligible articles, of which 82 met the inclusion criteria and were included in the review. These trials involved a median of 24 centres and 650 participants, and 87% involved two treatment arms. Recruitment, randomisation or treatment errors were reported in 32 in 82 trials (39%) that had a median of eight errors. The most commonly reported error was ineligible participants inadvertently being randomised. No mention of recruitment, randomisation or treatment errors was found in the remaining 50 of 82 trials (61%). Based on responses from 9 of the 15 corresponding authors who were contacted regarding recruitment, randomisation and treatment errors, between 1% and 100% of the errors that occurred in their trials were reported in the trial publications. Conclusion Recruitment, randomisation and treatment errors are common in individually randomised, phase III trials published in leading medical journals, but reporting practices are inadequate and reporting standards are needed. We recommend researchers report all such errors that occurred during the trial and describe how they were handled in trial publications to improve transparency in reporting of clinical trials.

The SPICE III study protocol and analysis plan: a randomised trial of early goaldirected sedation compared with standard care in mechanically ventilated patients

BACKGROUND

Sedation strategy in critically ill patients who are mechanically ventilated is influenced by patient-related factors, choice of sedative agent and the intensity or depth of sedation prescribed. The impact of sedation strategy on outcome, in particular when delivered early after initiation of mechanical ventilation, is uncertain.

OBJECTIVES

To present the protocol and analysis plan of a large randomised clinical trial investigating the effect of a sedation strategy, in critically ill patients who are mechanically ventilated, based on a protocol targeting light sedation using dexmedetomidine as the primary sedative, termed "early goal-directed sedation", compared with usual practice.

METHODS

This is a multinational randomised clinical trial in adult intensive care patients expected to require mechanical ventilation for longer than 24 hours. The main exclusion criteria include suspected or proven primary brain pathology or having already been intubated or sedated in an intensive care unit for longer than 12 hours. Randomisation occurs via a secured website with baseline stratification by site and suspected or proven sepsis. The primary outcome is 90-day all-cause mortality. Secondary outcomes include death, institutional dependency, cognitive function and health-related quality of life 180 days after randomisation, as well as deliriumfree, coma-free and ventilation-free days at 28 days after randomisation. A predefined subgroup analysis will also be conducted. Analyses will be on an intention-to-treat basis and in accordance with this pre-specified analysis plan.

CONCLUSION

SPICE III is an ongoing large scale clinical trial. Once completed, it will inform sedation practice in critically ill patients who are ventilated.

Impact of non-uniform correlation structure on sample size and power in multiple-period cluster randomised trials

Stepped wedge and cluster randomised crossover trials are examples of cluster randomised designs conducted over multiple time periods that are being used with increasing frequency in health research. Recent systematic reviews of both of these designs indicate that the within-cluster correlation is typically taken account of in the analysis of data using a random intercept mixed model, implying a constant correlation between any two individuals in the same cluster no matter how far apart in time they are measured: within-period and between-period intra-cluster correlations are assumed to be identical. Recently proposed extensions allow the within- and between-period intra-cluster correlations to differ, although these methods require that all between-period intra-cluster correlations are identical, which may not be appropriate in all situations. Motivated by a proposed intensive care cluster randomised trial, we propose an alternative correlation structure for repeated cross-sectional multiple-period cluster randomised trials in which the between-period intra-cluster correlation is allowed to decay depending on the distance between measurements. We present results for the variance of treatment effect estimators for varying amounts of decay, investigating the consequences of the variation in decay on sample size planning for stepped wedge, cluster crossover and multiple-period parallel-arm cluster randomised trials. We also investigate the impact of assuming constant between-period intra-cluster correlations instead of decaying between-period intra-cluster correlations. Our results indicate that in certain design configurations, including the one corresponding to the proposed trial, a correlation decay can have an important impact on variances of treatment effect estimators, and hence on sample size and power. An R Shiny app allows readers to interactively explore the impact of correlation decay.

Understanding the cluster randomised crossover design: a graphical illustraton of the components of variation and a sample size tutorial

BACKGROUND

In a cluster randomised crossover (CRXO) design, a sequence of interventions is assigned to a group, or 'cluster' of individuals. Each cluster receives each intervention in a separate period of time, forming 'cluster-periods'. Sample size calculations for CRXO trials need to account for both the cluster randomisation and crossover aspects of the design. Formulae are available for the two-period, two-intervention, cross-sectional CRXO design, however implementation of these formulae is known to be suboptimal. The aims of this tutorial are to illustrate the intuition behind the design; and provide guidance on performing sample size calculations.

METHODS

Graphical illustrations are used to describe the effect of the cluster randomisation and crossover aspects of the design on the correlation between individual responses in a CRXO trial. Sample size calculations for binary and continuous outcomes are illustrated using parameters estimated from the Australia and New Zealand Intensive Care Society - Adult Patient Database (ANZICS-APD) for patient mortality and length(s) of stay (LOS).

RESULTS

The similarity between individual responses in a CRXO trial can be understood in terms of three components of variation: variation in cluster mean response; variation in the cluster-period mean response; and variation between individual responses within a cluster-period; or equivalently in terms of the correlation between individual responses in the same cluster-period (within-cluster within-period correlation, WPC), and between individual responses in the same cluster, but in different periods (within-cluster between-period correlation, BPC). The BPC lies between zero and the WPC. When the WPC and BPC are equal the precision gained by crossover aspect of the CRXO design equals the precision lost by cluster randomisation. When the BPC is zero there is no advantage in a CRXO over a parallel-group cluster randomised trial. Sample size calculations illustrate that small changes in the specification of the WPC or BPC can increase the required number of clusters.

CONCLUSIONS

By illustrating how the parameters required for sample size calculations arise from the CRXO design and by providing guidance on both how to choose values for the parameters and perform the sample size calculations, the implementation of the sample size formulae for CRXO trials may improve.

Targeted anthelmintic treatment of parasitic gastroenteritis in first grazing season dairy calves using daily live weight gain as an indicator

Control of parasitic gastroenteritis in cattle is typically based on group treatments with anthelmintics, complemented by grazing management, where feasible. However, the almost inevitable evolution of resistance in parasitic nematodes to anthelmintics over time necessitates a reappraisal of their use in order to reduce selection pressure. One such approach is targeted selective treatment (TST), in which only individual animals that will most benefit are treated, rather than whole groups of at-risk cattle. This study was designed to assess the feasibility of implementing TST on three commercial farms, two of which were organic. A total of 104 first-grazing season (FGS), weaned dairy calves were enrolled in the study; each was weighed at monthly intervals from the start of the grazing season using scales or weigh-bands. At the same time dung and blood samples were collected in order to measure faecal egg counts (FEC) and plasma pepsinogen, respectively. A pre-determined threshhold weight gain of 0.75kg/day was used to determine those animals that would be treated; the anthelmintic used was eprinomectin. No individual animal received more than one treatment during the grazing season and all treatments were given in July or August; five animals were not treated at all because their growth rates consistently exceeded the threshold. Mean daily live weight gain over the entire grazing season ranged between 0.69 and 0.82kg/day on the three farms. Neither FEC nor pepsinogen values were significantly associated with live weight gain. Implementation of TST at farm level requires regular (monthly) handling of the animals and the use of weigh scales or tape, but can be integrated into farm management practices. This study has shown that acceptable growth rates can be achieved in FGS cattle with modest levels of treatment and correspondingly less exposure of their nematode populations to anthelmintics, which should mitigate selection pressure for resistance by increasing the size of the refugia in both hosts and pasture.

Serological lessons from the bovine lungworm Dictyocaulus viviparus: Antibody titre development is independent of the infection dose and reinfection shortens seropositivity

Infections with the bovine lungworm Dictyocaulus viviparus, the causative agent of parasitic bronchitis, are accompanied by substantial economic losses due to impacts on production, clinical respiratory disease or even death of diseased cattle. To detect lungworm antibodies in cattle, an enzyme-linked immunosorbent assay (ELISA) based on recombinant major sperm protein (MSP) has been developed. However, it remained unknown whether the infection dose influences antibody levels, and how acquired immunity influences antibody level patterns during reinfections. The latter may lead to low within-herd seroprevalence and thus to negative MSP-ELISA results in examination of bulk tank milk (BTM). Thus, infection experiments with 12 different doses ranging from 10 to 3000 D. viviparus larvae were performed to assess whether the antibody response is dose-dependent. Second, the impact of reinfections on the antibody response was evaluated in infection experiments, and third, antibody patterns in dairy cows during naturally occurring reinfections were assessed in a longitudinal field study based on individual milk samples. Results of this study demonstrate that the rise in MSP antibodies during first infection is dose-independent at infection doses of 25 lungworm larvae and above. However, following reinfections the magnitude and duration of the MSP antibody response are reduced or lacking, depending on the interval to reinfection. The field study revealed short periods of seropositivity as a common pattern in dairy cows subjected to natural D. viviparus reinfections. Low within-herd seroprevalence in dairy herds can thus be a result of continuous reinfections. Low infection doses should not be a barrier to serodiagnosis of lungworm infection in first-time infected cattle.

Modelling the impacts of pasture contamination and stocking rate for the development of targeted selective treatment strategies for Ostertagia ostertagi infection in calves

•

Stocking rate effect on design of targeted selective treatments (TST) was evaluated.

•

Initial pasture contamination effect on the design of TST was evaluated.

•

Different phenotypic traits and methods of selection for treatment were addressed.

•

Benefit was assessed as weight gain/frequency of resistant alleles in helminths.

•

Treatment according to threshold triggers of average daily gain was most beneficial.

A simulation study was carried out to assess whether variation in pasture contamination or stocking rate impact upon the optimal design of targeted selective treatment (TST) strategies. Two methods of TST implementation were considered: 1) treatment of a fixed percentage of a herd according to a given phenotypic trait, or 2) treatment of individuals that exceeded a threshold value for a given phenotypic trait. Four phenotypic traits, on which to base treatment were considered: 1) average daily bodyweight gain, 2) faecal egg count, 3) plasma pepsinogen, or 4) random selection. Each implementation method (fixed percentage or threshold treatment) and determinant criteria (phenotypic trait) was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The impact of pasture contamination on optimal TST strategy design was investigated by setting the initial pasture contamination to 100, 200 or 500 O. ostertagi L3/kg DM herbage; stocking rate was investigated at a low (3calves/ha), conventional (5 calves/ha) or high (7 calves/ha) stocking rates. When treating a fixed percentage of the herd, treatments according to plasma pepsinogen or random selection were identified as the most beneficial (i.e. resulted in the greatest BPR) for all levels of initial pasture contamination and all stocking rates. Conversely when treatments were administered according to threshold values ADG was most beneficial, and was identified as the best TST strategy (i.e. resulted in the greatest overall BPR) for all levels of initial pasture contamination and all stocking rates.

Protocol for a cluster randomised stepped wedge trial assessing the impact of a community-level hygiene intervention and a water intervention using riverbank filtration technology on diarrhoeal prevalence in India

INTRODUCTION

Diarrhoea is a leading cause of death globally, mostly occurring as a result of insufficient or unsafe water supplies, inadequate sanitation and poor hygiene. Our study aims to investigate the impact of a community-level hygiene education program and a water quality intervention using riverbank filtration (RBF) technology on diarrhoeal prevalence.

METHODS AND ANALYSIS

We have designed a stepped wedge cluster randomised trial to estimate the health impacts of our intervention in 4 rural villages in Karnataka, India. At baseline, surveys will be conducted in all villages, and householders will receive hygiene education. New pipelines, water storage tanks and taps will then be installed at accessible locations in each village and untreated piped river water will be supplied. A subsequent survey will evaluate the impact of hygiene education combined with improved access to greater water volumes for hygiene and drinking purposes (improved water quantity). Villages will then be randomly ordered and RBF-treated water (improved water quality) will be sequentially introduced into the 4 villages in a stepwise manner, with administration of surveys at each time point. The primary outcome is a 7-day period prevalence of self-reported diarrhoea. Secondary outcomes include self-reported respiratory and skin infections, and reported changes in hygiene practices, household water usage and water supply preference. River, tank and tap water from each village, and stored water from a subset of households, will be sampled to assess microbial and chemical quality.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Monash University Human Research Ethics Committee in Australia and The Energy and Resources Institute Institutional Ethics Committee in India. The results of the trial will be presented at conferences, published in peer-reviewed journals and disseminated to relevant stakeholders. This study is funded by an Australian National Health and Medical Research Council (NHMRC) project grant.

TRIAL REGISTRATION NUMBER

ACTRN12616001286437; pre-results.

Introduction to systematic reviews and meta-analysis

Systematic reviews provide a method for collating and synthesizing research, and are used to inform healthcare decision making by clinicians, consumers and policy makers. A core component of many systematic reviews is a meta-analysis, which is a statistical synthesis of results across studies. In this review article, we introduce meta-analysis, focusing on the different meta-analysis models, their interpretation, how a model should be selected and discuss potential threats to the validity of meta-analyses. We illustrate the application of meta-analysis using data from a review examining the effects of early use of inhaled corticosteroids in the emergency department treatment of acute asthma.

The quality of reporting in cluster randomised crossover trials: proposal for reporting items and an assessment of reporting quality

BACKGROUND

The cluster randomised crossover (CRXO) design is gaining popularity in trial settings where individual randomisation or parallel group cluster randomisation is not feasible or practical. Our aim is to stimulate discussion on the content of a reporting guideline for CRXO trials and to assess the reporting quality of published CRXO trials.

METHODS

We undertook a systematic review of CRXO trials. Searches of MEDLINE, EMBASE, and CINAHL Plus as well as citation searches of CRXO methodological articles were conducted to December 2014. Reporting quality was assessed against both modified items from 2010 CONSORT and 2012 cluster trials extension and other proposed quality measures.

RESULTS

Of the 3425 records identified through database searching, 83 trials met the inclusion criteria. Trials were infrequently identified as "cluster randomis(z)ed crossover" in title (n = 7, 8%) or abstract (n = 21, 25%), and a rationale for the design was infrequently provided (n = 20, 24%). Design parameters such as the number of clusters and number of periods were well reported. Discussion of carryover took place in only 17 trials (20%). Sample size methods were only reported in 58% (n = 48) of trials. A range of approaches were used to report baseline characteristics. The analysis method was not adequately reported in 23% (n = 19) of trials. The observed within-cluster within-period intracluster correlation and within-cluster between-period intracluster correlation for the primary outcome data were not reported in any trial. The potential for selection, performance, and detection bias could be evaluated in 30%, 81%, and 70% of trials, respectively.

CONCLUSIONS

There is a clear need to improve the quality of reporting in CRXO trials. Given the unique features of a CRXO trial, it is important to develop a CONSORT extension. Consensus amongst trialists on the content of such a guideline is essential.

A simulation model to investigate interactions between first season grazing calves and Ostertagia ostertagi

•

A deterministic model to address calf—O. ostertagi interactions was developed.

•

The model predicts performance and FEC for different infection intensities.

•

It performs well when validated against published data.

•

It does not account for calf genotypic variation.

•

A future aim is to develop a stochastic model to account for between host variation.

A dynamic, deterministic model was developed to investigate the consequences of parasitism with Ostertagia ostertagi, the most prevalent and economically important gastrointestinal parasite of cattle in temperate regions. Interactions between host and parasite were considered to predict the level of parasitism and performance of an infected calf. Key model inputs included calf intrinsic growth rate, feed quality and mode and level of infection. The effects of these varied inputs were simulated on a daily basis for key parasitological (worm burden, total egg output and faecal egg count) and performance outputs (feed intake and bodyweight) over a 6 month grazing period. Data from published literature were used to parameterise the model and its sensitivity was tested for uncertain parameters by a Latin hypercube sensitivity design. For the latter each parameter tested was subject to a 20% coefficient of variation. The model parasitological outputs were most sensitive to the immune rate parameters that affected overall worm burdens. The model predicted the expected larger worm burdens along with disproportionately greater body weight losses with increasing daily infection levels. The model was validated against published literature using graphical and statistical comparisons. Its predictions were quantitatively consistent with the parasitological outputs of published experiments in which calves were subjected to different infection levels. The consequences of model weaknesses are discussed and point towards model improvements. Future work should focus on developing a stochastic model to account for calf variation in performance and immune response; this will ultimately be used to test the effectiveness of different parasite control strategies in naturally infected calf populations.

The long-term mental health impact of peacekeeping: prevalence and predictors of psychiatric disorder

BACKGROUND

The mental health outcomes of military personnel deployed on peacekeeping missions have been relatively neglected in the military mental health literature.

AIMS

To assess the mental health impacts of peacekeeping deployments.

METHOD

In total, 1025 Australian peacekeepers were assessed for current and lifetime psychiatric diagnoses, service history and exposure to potentially traumatic events (PTEs). A matched Australian community sample was used as a comparator. Univariate and regression analyses were conducted to explore predictors of psychiatric diagnosis.

RESULTS

Peacekeepers had significantly higher 12-month prevalence of post-traumatic stress disorder (16.8%), major depressive episode (7%), generalised anxiety disorder (4.7%), alcohol misuse (12%), alcohol dependence (11.3%) and suicidal ideation (10.7%) when compared with the civilian comparator. The presence of these psychiatric disorders was most strongly and consistently associated with exposure to PTEs.

CONCLUSIONS

Veteran peacekeepers had significant levels of psychiatric morbidity. Their needs, alongside those of combat veterans, should be recognised within military mental health initiatives.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence.

Increased symptom reporting persists in 1990-1991 Gulf War veterans 20 years post deployment

BACKGROUND

Following the 1990-1991 Gulf War, Gulf War veterans (veterans) reported health symptoms more commonly than non-deployed groups. This article examines symptom persistence, incidence and prevalence 20 years on.

METHODS

In 2000-2003 and 2011-2012, a 63-item symptom checklist was administered to 697 veterans and 659 comparison group. Symptomatology was compared using log-binomial regression.

RESULTS

Both veterans and comparison group reported significantly increased prevalence (3-52%) over time in more than half the symptoms, with a similar overall rate of increase. Half the symptoms had higher incidence (risk-ratios ranged 1.43-1.50) and a quarter were more persistent (risk-ratios ranged 1.12-1.20) in veterans than the comparison group.

CONCLUSIONS

Symptomatology increased in both groups over time, but persisted to a similar extent and had higher incidence among veterans than the comparison group. The gap in symptom prevalence between the two groups remained unchanged. These findings suggest enduring health consequences of Gulf War service.

A re-randomisation design for clinical trials

Background

Recruitment to clinical trials is often problematic, with many trials failing to recruit to their target sample size. As a result, patient care may be based on suboptimal evidence from underpowered trials or non-randomised studies.

Methods

For many conditions patients will require treatment on several occasions, for example, to treat symptoms of an underlying chronic condition (such as migraines, where treatment is required each time a new episode occurs), or until they achieve treatment success (such as fertility, where patients undergo treatment on multiple occasions until they become pregnant). We describe a re-randomisation design for these scenarios, which allows each patient to be independently randomised on multiple occasions. We discuss the circumstances in which this design can be used.

Results

The re-randomisation design will give asymptotically unbiased estimates of treatment effect and correct type I error rates under the following conditions: (a) patients are only re-randomised after the follow-up period from their previous randomisation is complete; (b) randomisations for the same patient are performed independently; and (c) the treatment effect is constant across all randomisations. Provided the analysis accounts for correlation between observations from the same patient, this design will typically have higher power than a parallel group trial with an equivalent number of observations.

Conclusions

If used appropriately, the re-randomisation design can increase the recruitment rate for clinical trials while still providing an unbiased estimate of treatment effect and correct type I error rates. In many situations, it can increase the power compared to a parallel group design with an equivalent number of observations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12874-015-0082-2) contains supplementary material, which is available to authorized users.

A telephone survey of factors affecting willingness to participate in health research surveys

Background

In recent years, reduced participation has been encountered across all epidemiological study designs, both in terms of non-response as well as refusal. A low response rate may reduce the statistical power but, more importantly, results may not be generalizable to the wider community.

Methods

In a telephone survey of 1413 randomly selected members of the Australian general population and of 690 participants sourced from previous studies, we examined factors affecting people’s stated willingness to participate in health research.

Results

The majority of participants (61 %) expressed willingness to participate in health research in general but the percentage increased when provided with more specific information about the research. People were more willing if they have personal experience of the disease under study, and if the study was funded by government or charity rather than pharmaceutical companies.

Participants from previous studies, older people and women were the groups most willing to participate. Younger men preferred online surveys, older people a written questionnaire, and few participants in any age and sex groups preferred a telephone questionnaire.

Conclusion

Despite a trend toward reduced participation rates, most participants expressed their willingness to participate in health research. However, when seeking participants, researchers should be concrete and specific about the nature of the research they want to carry out. The preferred method of recommended contact varies with the demographic characteristics.