Recruitment and retention of participants in randomised controlled trials: a review of trials funded and published by the United Kingdom Health Technology Assessment Programme

BACKGROUND

Substantial amounts of public funds are invested in health research worldwide. Publicly funded randomised controlled trials (RCTs) often recruit participants at a slower than anticipated rate. Many trials fail to reach their planned sample size within the envisaged trial timescale and trial funding envelope.

OBJECTIVES

To review the consent, recruitment and retention rates for single and multicentre randomised control trials funded and published by the UK's National Institute for Health Research (NIHR) Health Technology Assessment (HTA) Programme.

DATA SOURCES AND STUDY SELECTION

HTA reports of individually randomised single or multicentre RCTs published from the start of 2004 to the end of April 2016 were reviewed.

DATA EXTRACTION

Information was extracted, relating to the trial characteristics, sample size, recruitment and retention by two independent reviewers.

MAIN OUTCOME MEASURES

Target sample size and whether it was achieved; recruitment rates (number of participants recruited per centre per month) and retention rates (randomised participants retained and assessed with valid primary outcome data).

RESULTS

This review identified 151 individually RCTs from 787 NIHR HTA reports. The final recruitment target sample size was achieved in 56% (85/151) of the RCTs and more than 80% of the final target sample size was achieved for 79% of the RCTs (119/151). The median recruitment rate (participants per centre per month) was found to be 0.92 (IQR 0.43-2.79) and the median retention rate (proportion of participants with valid primary outcome data at follow-up) was estimated at 89% (IQR 79-97%).

CONCLUSIONS

There is considerable variation in the consent, recruitment and retention rates in publicly funded RCTs. Investigators should bear this in mind at the planning stage of their study and not be overly optimistic about their recruitment projections.

Recruiting vulnerable populations into research: a systematic review of recruitment interventions

BACKGROUND

Members of vulnerable populations are underrepresented in research studies.

OBJECTIVE

To evaluate and synthesize the evidence regarding interventions to enhance enrollment of vulnerable populations into health research studies.

DATA SOURCES

Studies were identified by searching MEDLINE, the Web of Science database, personal sources, hand searching of related journals, and article references. Studies that contained data on recruitment interventions for vulnerable populations (minority, underserved, poor, rural, urban, or inner city) and for which the parent study (study for which recruitment was taking place) was an intervention study were included. A total of 2,648 study titles were screened and 48 articles met inclusion criteria, representing 56 parent studies. Two investigators extracted data from each study.

RESULTS

African Americans were the most frequently targeted population (82% of the studies), while 46% targeted Hispanics/Latinos. Many studies assessed 2 or more interventions, including social marketing (82% of studies), community outreach (80%), health system recruitment (52%), and referrals (28%). The methodologic rigor varied substantially. Only 40 studies (71%) incorporated a control group and 21% used statistical analysis to compare interventions. Social marketing, health system, and referral recruitment were each found to be the most successful intervention about 35-45% of the studies in which they were attempted, while community outreach was the most successful intervention in only 2 of 16 studies (13%) in which it was employed. People contacted as a result of social marketing were no less likely to enroll than people contacted through other mechanisms.

CONCLUSIONS

Further work with greater methodologic rigor is needed to identify evidence-based strategies for increasing minority enrollment in research studies; community outreach, as an isolated strategy, may be less successful than other strategies.

Cxcl8 (IL-8) mediates neutrophil recruitment and behavior in the zebrafish inflammatory response

Neutrophils play a pivotal role in the innate immune response. The small cytokine CXCL8 (also known as IL-8) is known to be one of the most potent chemoattractant molecules that, among several other functions, is responsible for guiding neutrophils through the tissue matrix until they reach sites of injury. Unlike mice and rats that lack a CXCL8 homolog, zebrafish has two distinct CXCL8 homologs: Cxcl8-l1 and Cxcl8-l2. Cxcl8-l1 is known to be upregulated under inflammatory conditions caused by bacterial or chemical insult but until now the role of Cxcl8s in neutrophil recruitment has not been studied. In this study we show that both Cxcl8 genes are upregulated in response to an acute inflammatory stimulus, and that both are crucial for normal neutrophil recruitment to the wound and normal resolution of inflammation. Additionally, we have analyzed neutrophil migratory behavior through tissues to the site of injury in vivo, using open-access phagocyte tracking software PhagoSight. Surprisingly, we observed that in the absence of these chemokines, the speed of the neutrophils migrating to the wound was significantly increased in comparison with control neutrophils, although the directionality was not affected. Our analysis suggests that zebrafish may possess a subpopulation of neutrophils whose recruitment to inflamed areas occurs independently of Cxcl8 chemokines. Moreover, we report that Cxcl8-l2 signaled through Cxcr2 for inducing neutrophil recruitment. Our study, therefore, confirms the zebrafish as an excellent in vivo model to shed light on the roles of CXCL8 in neutrophil biology.

Interventions to improve recruitment and retention in clinical trials: a survey and workshop to assess current practice and future priorities

BACKGROUND

Despite significant investment in infrastructure many trials continue to face challenges in recruitment and retention. We argue that insufficient focus has been placed on the development and testing of recruitment and retention interventions.

METHODS

In this current paper, we summarize existing reviews about interventions to improve recruitment and retention. We report survey data from Clinical Trials Units in the United Kingdom to indicate the range of interventions used by these units to encourage recruitment and retention. We present the views of participants in a recent workshop and a priority list of recruitment interventions for evaluation (determined by voting among workshop participants). We also discuss wider issues concerning the testing of recruitment interventions.

RESULTS

Methods used to encourage recruitment and retention were categorized as: patient contact, patient convenience, support for recruiters, monitoring and systems, incentives, design, resources, and human factors. Interventions felt to merit investigation by respondents fell into three categories: training site staff, communication with patients, and incentives.

CONCLUSIONS

Significant resources continue to be invested into clinical trials and other high quality studies, but recruitment remains a significant challenge. Adoption of innovative methods to develop, test, and implement recruitment interventions are required.

The impact of non-response bias due to sampling in public health studies: A comparison of voluntary versus mandatory recruitment in a Dutch national survey on adolescent health

BACKGROUND

In public health monitoring of young people it is critical to understand the effects of selective non-response, in particular when a controversial topic is involved like substance abuse or sexual behaviour. Research that is dependent upon voluntary subject participation is particularly vulnerable to sampling bias. As respondents whose participation is hardest to elicit on a voluntary basis are also more likely to report risk behaviour, this potentially leads to underestimation of risk factor prevalence. Inviting adolescents to participate in a home-sent postal survey is a typical voluntary recruitment strategy with high non-response, as opposed to mandatory participation during school time. This study examines the extent to which prevalence estimates of adolescent health-related characteristics are biased due to different sampling methods, and whether this also biases within-subject analyses.

METHODS

Cross-sectional datasets collected in 2011 in Twente and IJsselland, two similar and adjacent regions in the Netherlands, were used. In total, 9360 youngsters in a mandatory sample (Twente) and 1952 youngsters in a voluntary sample (IJsselland) participated in the study. To test whether the samples differed on health-related variables, we conducted both univariate and multivariable logistic regression analyses controlling for any demographic difference between the samples. Additional multivariable logistic regressions were conducted to examine moderating effects of sampling method on associations between health-related variables.

RESULTS

As expected, females, older individuals, as well as individuals with higher education levels, were over-represented in the voluntary sample, compared to the mandatory sample. Respondents in the voluntary sample tended to smoke less, consume less alcohol (ever, lifetime, and past four weeks), have better mental health, have better subjective health status, have more positive school experiences and have less sexual intercourse than respondents in the mandatory sample. No moderating effects were found for sampling method on associations between variables.

CONCLUSIONS

This is one of first studies to provide strong evidence that voluntary recruitment may lead to a strong non-response bias in health-related prevalence estimates in adolescents, as compared to mandatory recruitment. The resulting underestimation in prevalence of health behaviours and well-being measures appeared large, up to a four-fold lower proportion for self-reported alcohol consumption. Correlations between variables, though, appeared to be insensitive to sampling bias.

Unsuccessful trial accrual and human subjects protections: an empirical analysis of recently closed trials

BACKGROUND

Ethical evaluation of risk-benefit in clinical trials is premised on the achievability of resolving research questions motivating an investigation.

OBJECTIVE

To determine the fraction and number of patients enrolled in trials that were at risk of not meaningfully addressing their primary research objective due to unsuccessful patient accrual.

METHODS

We used the National Library of Medicine clinical trial registry to capture all initiated phases 2 and 3 intervention clinical trials that were registered as closed in 2011. We then determined the number that had been terminated due to unsuccessful accrual and the number that had closed after less than 85% of the target number of human subjects had been enrolled. Five factors were tested for association with unsuccessful accrual.

RESULTS

Of 2579 eligible trials, 481 (19%) either terminated for failed accrual or completed with less than 85% expected enrolment, seriously compromising their statistical power. Factors associated with unsuccessful accrual included greater number of eligibility criteria (p = 0.013), non-industry funding (25% vs 16%, p < 0.0001), earlier trial phase (23% vs 16%, p < 0.0001), fewer number of research sites at trial completion (p < 0.0001) and at registration (p < 0.0001), and an active (non-placebo) comparator (23% vs 16%, p < 0.001).

CONCLUSION

A total of 48,027 patients had enrolled in trials closed in 2011 who were unable to answer the primary research question meaningfully. Ethics bodies, investigators, and data monitoring committees should carefully scrutinize trial design, recruitment plans, and feasibility of achieving accrual targets when designing and reviewing trials, monitor accrual once initiated, and take corrective action when accrual is lagging.

Symbiotic Macrophage-Glioma Cell Interactions Reveal Synthetic Lethality in PTEN-Null Glioma

Heterotypic interactions across diverse cell types can enable tumor progression and hold the potential to expand therapeutic interventions. Here, combined profiling and functional studies of glioma cells in glioblastoma multiforme (GBM) models establish that PTEN deficiency activates YAP1, which directly upregulates lysyl oxidase (LOX) expression. Mechanistically, secreted LOX functions as a potent macrophage chemoattractant via activation of the β1 integrin-PYK2 pathway in macrophages. These infiltrating macrophages secrete SPP1, which sustains glioma cell survival and stimulates angiogenesis. In PTEN-null GBM models, LOX inhibition markedly suppresses macrophage infiltration and tumor progression. Correspondingly, YAP1-LOX and β1 integrin-SPP1 signaling correlates positively with higher macrophage density and lower overall survival in GBM patients. This symbiotic glioma-macrophage interplay provides therapeutic targets specifically for PTEN-deficient GBM.

Host diversity begets parasite diversity: bird final hosts and trematodes in snail intermediate hosts

An unappreciated facet of biodiversity is that rich communities and high abundance may foster parasitism. For parasites that sequentially use different host species throughout complex life cycles, parasite diversity and abundance in 'downstream' hosts should logically increase with the diversity and abundance of 'upstream' hosts (which carry the preceding stages of parasites). Surprisingly, this logical assumption has little empirical support, especially regarding metazoan parasites. Few studies have attempted direct tests of this idea and most have lacked the appropriate scale of investigation. In two different studies, we used time-lapse videography to quantify birds at fine spatial scales, and then related bird communities to larval trematode communities in snail populations sampled at the same small spatial scales. Species richness, species heterogeneity and abundance of final host birds were positively correlated with species richness, species heterogeneity and abundance of trematodes in host snails. Such community-level interactions have rarely been demonstrated and have implications for community theory, epidemiological theory and ecosystem management.

Human telomerase: biogenesis, trafficking, recruitment, and activation

In this review, Schmidt and Cech cover human telomerase biogenesis, trafficking, and activation, comparing key aspects with the analogous events in other species.

Telomerase is the ribonucleoprotein enzyme that catalyzes the extension of telomeric DNA in eukaryotes. Recent work has begun to reveal key aspects of the assembly of the human telomerase complex, its intracellular trafficking involving Cajal bodies, and its recruitment to telomeres. Once telomerase has been recruited to the telomere, it appears to undergo a separate activation step, which may include an increase in its repeat addition processivity. This review covers human telomerase biogenesis, trafficking, and activation, comparing key aspects with the analogous events in other species.

Serine phosphorylation of SR proteins is required for their recruitment to sites of transcription in vivo

Expression of most RNA polymerase II transcripts requires the coordinated execution of transcription, splicing, and 3' processing. We have previously shown that upon transcriptional activation of a gene in vivo, pre-mRNA splicing factors are recruited from nuclear speckles, in which they are concentrated, to sites of transcription (Misteli, T., J.F. Cáceres, and D.L. Spector. 1997. Nature. 387:523-527). This recruitment process appears to spatially coordinate transcription and pre-mRNA splicing within the cell nucleus. Here we have investigated the molecular basis for recruitment by analyzing the recruitment properties of mutant splicing factors. We show that multiple protein domains are required for efficient recruitment of SR proteins from nuclear speckles to nascent RNA. The two types of modular domains found in the splicing factor SF2/ ASF exert distinct functions in this process. In living cells, the RS domain functions in the dissociation of the protein from speckles, and phosphorylation of serine residues in the RS domain is a prerequisite for this event. The RNA binding domains play a role in the association of splicing factors with the target RNA. These observations identify a novel in vivo role for the RS domain of SR proteins and suggest a model in which protein phosphorylation is instrumental for the recruitment of these proteins to active sites of transcription in vivo.

Using Social Media as a Research Recruitment Tool: Ethical Issues and Recommendations

The use of social media as a recruitment tool for research with humans is increasing, and likely to continue to grow. Despite this, to date there has been no specific regulatory guidance and there has been little in the bioethics literature to guide investigators and institutional review boards (IRBs) faced with navigating the ethical issues such use raises. We begin to fill this gap by first defending a nonexceptionalist methodology for assessing social media recruitment; second, examining respect for privacy and investigator transparency as key norms governing social media recruitment; and, finally, analyzing three relatively novel aspects of social media recruitment: (i) the ethical significance of compliance with website "terms of use"; (ii) the ethics of recruiting from the online networks of research participants; and (iii) the ethical implications of online communication from and between participants. Two checklists aimed at guiding investigators and IRBs through the ethical issues are included as appendices.

The role of cultural diversity climate in recruitment, promotion, and retention of faculty in academic medicine

BACKGROUND

Ethnic diversity among physicians may be linked to improved access and quality of care for minorities. Academic medical institutions are challenged to increase representation of ethnic minorities among health professionals.

OBJECTIVES

To explore the perceptions of physician faculty regarding the following: (1) the institution's cultural diversity climate and (2) facilitators and barriers to success and professional satisfaction in academic medicine within this context.

DESIGN

Qualitative study using focus groups and semi-structured interviews.

PARTICIPANTS

Nontenured physicians in the tenure track at the Johns Hopkins University School of Medicine.

APPROACH

Focus groups and interviews were audio-taped, transcribed verbatim, and reviewed for thematic content in a 3-stage independent review/adjudication process.

RESULTS

Study participants included 29 faculty representing 9 clinical departments, 4 career tracks, and 4 ethnic groups. In defining cultural diversity, faculty noted visible (race/ethnicity, foreign-born status, gender) and invisible (religion, sexual orientation) dimensions. They believe visible dimensions provoke bias and cumulative advantages or disadvantages in the workplace. Minority and foreign-born faculty report ethnicity-based disparities in recruitment and subtle manifestations of bias in the promotion process. Minority and majority faculty agree that ethnic differences in prior educational opportunities lead to disparities in exposure to career options, and qualifications for and subsequent recruitment to training programs and faculty positions. Minority faculty also describe structural barriers (poor retention efforts, lack of mentorship) that hinder their success and professional satisfaction after recruitment. To effectively manage the diversity climate, our faculty recommended 4 strategies for improving the psychological climate and structural diversity of the institution.

CONCLUSIONS

Soliciting input from faculty provides tangible ideas regarding interventions to improve an institution's diversity climate.

Framing the issues: moral distress in health care

Moral distress in health care has been identified as a growing concern and a focus of research in nursing and health care for almost three decades. Researchers and theorists have argued that moral distress has both short and long-term consequences. Moral distress has implications for satisfaction, recruitment and retention of health care providers and implications for the delivery of safe and competent quality patient care. In over a decade of research on ethical practice, registered nurses and other health care practitioners have repeatedly identified moral distress as a concern and called for action. However, research and action on moral distress has been constrained by lack of conceptual clarity and theoretical confusion as to the meaning and underpinnings of moral distress. To further examine these issues and foster action on moral distress, three members of the University of Victoria/University of British Columbia (UVIC/UVIC) nursing ethics research team initiated the development and delivery of a multi-faceted and interdisciplinary symposium on Moral Distress with international experts, researchers, and practitioners. The goal of the symposium was to develop an agenda for action on moral distress in health care. We sought to develop a plan of action that would encompass recommendations for education, practice, research and policy. The papers in this special issue of HEC Forum arose from that symposium. In this first paper, we provide an introduction to moral distress; make explicit some of the challenges associated with theoretical and conceptual constructions of moral distress; and discuss the barriers to the development of research, education, and policy that could, if addressed, foster action on moral distress in health care practice. The following three papers were written by key international experts on moral distress, who explore in-depth the issues in three arenas: education, practice, research. In the fifth and last paper in the series, we highlight key insights from the symposium and the papers in the series, propose to redefine moral distress, and outline directions for an agenda for action on moral distress in health care.

Recruitment of minority and underserved populations in the United States: the Centers for Population Health and Health Disparities experience

OBJECTIVE

The recruitment of minority and underserved individuals to research studies is often problematic. The purpose of this study was to describe the recruitment experiences of projects that actively recruited minority and underserved populations as part of The Centers for Population Health and Health Disparities (CPHHD) initiative.

METHODS

Principal investigators and research staff from 17 research projects at eight institutions across the United States were surveyed about their recruitment experiences. Investigators reported the study purpose and design, recruitment methods employed, recruitment progress, problems or challenges to recruitment, strategies used to address these problems, and difficulties resulting from Institutional Review Board (IRB) or Health Insurance Portability and Accountability Act of 1996 (HIPAA) requirements. Additionally, information was collected about participant burden and compensation. Burden was classified on a three-level scale. Recruitment results were reported as of March 31, 2007.

RESULTS

Recruitment attainment ranged from 52% to 184% of the participant recruitment goals. Commonly reported recruitment problems included administrative issues, and difficulties with establishing community partnerships and contacting potential participants. Long study questionnaires, extended follow-up, and narrow eligibility criteria were also problematic. The majority of projects reported difficulties with IRB approvals, though few reported issues related to HIPAA requirements. Attempted solutions to recruitment problems varied across Centers and included using multiple recruitment sites and sources and culturally appropriate invitations to participate. Participant burden and compensation varied widely across the projects, however, accrual appeared to be inversely associated with the amount of participant burden for each project.

CONCLUSION

Recruitment of minority and underserved populations to clinical trials is necessary to increase study generalizbility and reduce health disparities. Our results demonstrate the importance of flexible study designs which allow adaptation to recruitment challenges. These experiences also highlight the importance of involving community members and reducing participant burden to achieve success in recruiting individuals from minority and underserved populations.

Monocytes induce reversible focal changes in vascular endothelial cadherin complex during transendothelial migration under flow

The vascular endothelial cell cadherin complex (VE-cadherin, alpha-, beta-, and gamma-catenin, and p120/p100) localizes to adherens junctions surrounding vascular endothelial cells and may play a critical role in the transendothelial migration of circulating blood leukocytes. Previously, we have reported that neutrophil adhesion to human umbilical vein endothelial cell (HUVEC) monolayers, under static conditions, results in a dramatic loss of the VE-cadherin complex. Subsequent studies by us and others (Moll, T., E. Dejana, and D. Vestweber. 1998. J. Cell Biol. 140:403-407) suggested that this phenomenon might reflect degradation by neutrophil proteases released during specimen preparation. We postulated that some form of disruption of the VE-cadherin complex might, nonetheless, be a physiological process during leukocyte transmigration. In the present study, the findings demonstrate a specific, localized effect of migrating leukocytes on the VE-cadherin complex in cytokine-activated HUVEC monolayers. Monocytes and in vitro differentiated U937 cells induce focal loss in the staining of VE-cadherin, alpha-catenin, beta-catenin, and plakoglobin during transendothelial migration under physiological flow conditions. These events are inhibited by antibodies that prevent transendothelial migration and are reversed following transmigration. Together, these data suggest that an endothelial-dependent step of transient and focal disruption of the VE-cadherin complex occurs during leukocyte transmigration.

Addressing the crisis of GP recruitment and retention: a systematic review

BACKGROUND

The numbers of GPs and training places in general practice are declining, and retaining GPs in their practices is an increasing problem.

AIM

To identify evidence on different approaches to retention and recruitment of GPs, such as intrinsic versus extrinsic motivational determinants.

DESIGN AND SETTING

Synthesis of qualitative and quantitative research using seven electronic databases from 1990 onwards (Medline, Embase, Cochrane Library, Health Management Information Consortium [HMIC], Cumulative Index to Nursing and Allied Health Literature (Cinahl), PsycINFO, and the Turning Research Into Practice [TRIP] database).

METHOD

A qualitative approach to reviewing the literature on recruitment and retention of GPs was used. The studies included were English-language studies from Organisation for Economic Cooperation and Development countries. The titles and abstracts of 138 articles were reviewed and analysed by the research team.

RESULTS

Some of the most important determinants to increase recruitment in primary care were early exposure to primary care practice, the fit between skills and attributes, and a significant experience in a primary care setting. Factors that seemed to influence retention were subspecialisation and portfolio careers, and job satisfaction. The most important determinants of recruitment and retention were intrinsic and idiosyncratic factors, such as recognition, rather than extrinsic factors, such as income.

CONCLUSION

Although the published evidence relating to GP recruitment and retention is limited, and most focused on attracting GPs to rural areas, the authors found that there are clear overlaps between strategies to increase recruitment and retention. Indeed, the most influential factors are idiosyncratic and intrinsic to the individuals.

A structural and functional ground plan for neurons in the hindbrain of zebrafish

The vertebrate hindbrain contains various sensory-motor networks controlling movements of the eyes, jaw, head, and body. Here we show that stripes of neurons with shared neurotransmitter phenotype that extend throughout the hindbrain of young zebrafish reflect a broad underlying structural and functional patterning. The neurotransmitter stripes contain cell types with shared gross morphologies and transcription factor markers. Neurons within a stripe are stacked systematically by extent and location of axonal projections, input resistance, and age, and are recruited along the axis of the stripe during behavior. The implication of this pattern is that the many networks in hindbrain are constructed from a series of neuronal components organized into stripes that are ordered from top to bottom according to a neuron's age, structural and functional properties, and behavioral roles. This simple organization probably forms a foundation for the construction of the networks underlying the many behaviors produced by the hindbrain.

Perspectives on barriers and facilitators to minority recruitment for clinical trials among cancer center leaders, investigators, research staff, and referring clinicians: enhancing minority participation in clinical trials (EMPaCT)

BACKGROUND

The study of disparities in minority recruitment to cancer clinical trials has focused primarily on inquiries among minority populations. Yet very little is known about the perceptions of individuals actively involved in minority recruitment to clinical trials within cancer centers. Therefore, the authors assessed the perspectives of cancer center clinical and research personnel on barriers and facilitators to minority recruitment.

METHODS

In total, 91 qualitative interviews were conducted at 5 US cancer centers among 4 stakeholder groups: cancer center leaders, principal investigators, research staff, and referring clinicians. All interviews were recorded and transcribed. Qualitative analyses of response data was focused on identifying prominent themes related to barriers and facilitators to minority recruitment.

RESULTS

The perspectives of the 4 stakeholder groups were largely overlapping with some variations based on their unique roles in minority recruitment. Four prominent themes were identified: 1) racial and ethnic minorities are influenced by varying degrees of skepticism related to trial participation, 2) potential minority participants often face multilevel barriers that preclude them from being offered an opportunity to participate in a clinical trial, 3) facilitators at both the institutional and participant level potentially encourage minority recruitment, and 4) variation between internal and external trial referral procedures may limit clinical trial opportunities for racial and ethnic minorities.

CONCLUSIONS

Multilevel approaches are needed to address barriers and optimize facilitators within cancer centers to enhance minority recruitment for cancer clinical trials.

Recruitment of mental health survey participants using Internet advertising: content, characteristics and cost effectiveness

Postal and telephone survey research is threatened by declining response rates and high cost. Online recruitment is becoming more popular, although there is little empirical evidence about its cost-effectiveness or the representativeness of online samples. There is also limited research on optimal strategies for developing advertising content for online recruitment. The present study aimed to assess these aspects of online recruitment. Two mental health surveys used advertisements within a social network website (Facebook) to recruit adult Australian participants. The initial survey used advertisements linking directly to an external survey website, and recruited 1283 participants at $9.82 per completed survey. A subsequent survey used advertisements linking to a Facebook page that featured links to the external survey, recruiting 610 participants at $1.51 per completion. Both surveys were more cost-effective than similar postal surveys conducted previously, which averaged $19.10 per completion. Online and postal surveys both had somewhat unrepresentative samples. However, online surveys tended to be more successful in recruiting hard-to-reach populations. Advertising using "problem" terminology was more effective than "positive" terminology, while there was no significant effect of altruistic versus self-gain terminology. Online recruitment is efficient, flexible and cost-effective, suggesting that online recruitment has considerable potential for specific research designs.

Trail pheromones: an integrative view of their role in social insect colony organization

Trail pheromones do more than simply guide social insect workers from point A to point B. Recent research has revealed additional ways in which they help to regulate colony foraging, often via positive and negative feedback processes that influence the exploitation of the different resources that a colony has knowledge of. Trail pheromones are often complementary or synergistic with other information sources, such as individual memory. Pheromone trails can be composed of two or more pheromones with different functions, and information may be embedded in the trail network geometry. These findings indicate remarkable sophistication in how trail pheromones are used to regulate colony-level behavior, and how trail pheromones are used and deployed at the individual level.

Associations between motor unit action potential parameters and surface EMG features

The surface interference EMG signal provides some information on the neural drive to muscles. However, the association between neural drive to muscle and muscle activation has long been debated with controversial indications due to the unavailability of motor unit population data. In this study, we clarify the potential and limitations of interference EMG analysis to infer motor unit recruitment strategies with an experimental investigation of several concurrently active motor units and of the associated features of the surface EMG. For this purpose, we recorded high-density surface EMG signals during linearly increasing force contractions of the tibialis anterior muscle, up to 70% of maximal force. The recruitment threshold (RT), conduction velocity (MUCV), median frequency (MDF_MU), and amplitude (RMS_MU) of action potentials of 587 motor units from 13 individuals were assessed and associated with features of the interference EMG. MUCV was positively associated with RT (R² = 0.64 ± 0.14), whereas MDF_MU and RMS_MU showed a weaker relation with RT (R² = 0.11 ± 0.11 and 0.39 ± 0.24, respectively). Moreover, the changes in average conduction velocity estimated from the interference EMG predicted well the changes in MUCV (R² = 0.71), with a strong association to ankle dorsiflexion force (R² = 0.81 ± 0.12). Conversely, both the average EMG MDF and RMS were poorly associated with motor unit recruitment. These results clarify the limitations of EMG spectral and amplitude analysis in inferring the neural strategies of muscle control and indicate that, conversely, the average conduction velocity could provide relevant information on these strategies.NEW & NOTEWORTHY The surface EMG provides information on the neural drive to muscles. However, the associations between EMG features and neural drive have been long debated due to unavailability of motor unit population data. Here, by using novel highly accurate decomposition of the EMG, we related motor unit population behavior to a wide range of voluntary forces. The results fully clarify the potential and limitation of the surface EMG to provide estimates of the neural drive to muscles.

An essential role for tumor necrosis factor in natural killer cell-mediated tumor rejection in the peritoneum

Natural killer (NK) cells are thought to provide the first line of defence against tumors, particularly major histocompatibility complex (MHC) class I- variants. We have confirmed in C57BL/6 (B6) mice lacking perforin that peritoneal growth of MHC class I- RMA-S tumor cells in unprimed mice is controlled by perforin-dependent cytotoxicity mediated by CD3(-) NK1.1(+) cells. Furthermore, we demonstrate that B6 mice lacking tumor necrosis factor (TNF) are also significantly defective in their rejection of RMA-S, despite the fact that RMA-S is insensitive to TNF in vitro and that spleen NK cells from B6 and TNF-deficient mice are equally lytic towards RMA-S. NK cell recruitment into the peritoneum was abrogated in TNF-deficient mice challenged with RMA-S or RM-1, a B6 MHC class I- prostate carcinoma, compared with B6 or perforin-deficient mice. The reduced NK cell migration to the peritoneum of TNF-deficient mice correlated with the defective NK cell response to tumor in these mice. By contrast, a lack of TNF did not affect peptide-specific cytotoxic T lymphocyte-mediated rejection of tumor from the peritoneum of preimmunized mice. Overall, these data show that NK cells delivering perforin are the major effectors of class I- tumor rejection in the peritoneum, and that TNF is specifically critical for their recruitment to the peritoneum.

Recruitment of endogenous bone marrow mesenchymal stem cells towards injured liver

Recent studies suggest that mesenchymal stem cells (MSCs) possess a greater differentiation potential than once thought and that they have the capacity to regenerate damaged tissues/organs. However, the evidence is insufficient, and the mechanism governing the recruitment and homing of MSCs to these injured sites is not well understood. We first examined the MSCs circulating in peripheral blood and then performed chemotaxis, wound healing and tubule-formation assays to investigate the migration capability of mouse bone marrow MSCs (mBM-MSCs) in response to liver-injury signals. In addition, BM-MSCs from donor enhanced green fluorescent protein transgenic male mice were transplanted into liver-injured co-isogenic female recipients, either by intra-bone marrow injection or through the caudal vein, to allow in vivo tracking analysis of the cell fate after transplantation. Donor-derived cells were analysed by in vivo imaging analysis, PCR, flow cytometry and frozen sections. Microarray and real-time PCR were used for chemokine/cytokine and receptor analyses. We successfully isolated circulating MSCs in peripheral blood of liver-injured mice and provided direct evidence that mBM-MSCs could be mobilized into the circulation and recruited into the liver after stimulation of liver injury. CCR9, CXCR4 and c-MET were essential for directing cellular migration towards the injured liver. The recruited mBM-MSCs may play different roles, including hepatic fate specification and down-regulation of the activity of hepatic stellate cells which inhibits over-accumulation of collagen and development of liver fibrosis. Our results provide new insights into liver repair involving endogenous BM-MSCs and add new information for consideration when developing clinical protocols involving the MSCs.

Acute lung injury and acute respiratory distress syndrome

Every year, more information accumulates about the possibility of treating patients with acute lung injury or acute respiratory distress syndrome with specially designed mechanical ventilation strategies. Ventilator modes, positive end-expiratory pressure settings, and recruitment maneuvers play a major role in these strategies. However, what can we take from these experimental and clinical data to the clinical practice? In this article, we discuss substantial options of mechanical ventilation together with some adjunctive therapeutic measures, such as prone positioning and inhalation of nitric oxide.

Challenges in recruitment and retention of clinical trial subjects

BACKGROUND

Successful recruitment of patients is known to be one of the most challenging aspects in conduct of randomized controlled trials. Inadequate patient retention during conduct of trial affects conclusive results.

OBJECTIVE

To assess the level of challenges faced by Indian investigators in recruitment and retention of trial subjects.

METHODS

We developed a survey questionnaire on challenges encountered by investigators in subject recruitment and retention which was hosted on a web portal.

RESULTS

Seventy-three investigators from India participated in the survey. The frequently encountered challenges in subject recruitment were complexity of study protocol (38%), lack of awareness about clinical trials in patients (37%), and sociocultural issues related to trial participation (37%). About 63% of participants strongly agreed that creating a positive awareness about clinical trials among people through press and media, having a dedicated clinical research coordinator for trial (50.7%), and designing a recruitment strategy prior to study initiation (46.6%) would enhance recruitment. Almost 50.7% of participants agreed that interacting with medical community in vicinity of the study site and educating patients about clinical trials during routine outpatient department visits (46.6%) would enhance recruitment. Experiencing a serious adverse event, subject's fear for study procedures (47%) and side effects (44%) were thought to have a moderate effect on subject retention.

CONCLUSION

Our survey has put forth factors related to negative publicity by media, lack of patient education about clinical trials; complex study designs are barriers to clinical trial recruitment in India. It is essential to devise innovative and effective strategies focusing on education of public and mass media about clinical research in India.