6
Design Considerations: Recruitment and Retention

This chapter explores the influence of recruitment and retention on trial design and conduct. As discussed in Chapter 2, late-stage biomedical HIV prevention trials require investigators to enroll several hundred to several thousand participants at one or multiple sites, and often follow them for several years. A slow accrual rate or poor retention of trial participants may result in underpowered or biased results. To ensure confidence in trial outcomes, it is essential for investigators to meet the study’s accrual goals and maximize participant retention. Yet meeting each of these goals can be challenging in resource-poor settings with limited infrastructure and highly mobile and diverse populations (Hill, 2004). For example, a recent trial in Tanzania evaluating herpes simplex virus (HSV-2) suppression to reduce HIV infection reported a retention rate of only 60 percent (Watson-Jones et al., 2007).

Despite the critical threat that inadequate recruitment and retention pose to trial validity, there is little empirical data on the effectiveness of alternative recruitment and retention strategies (Lovato et al., 1997; Mapstone et al., 2007; Robinson et al., 2007; Villacorta et al., 2007). Thus, most of what the committee describes below is drawn from publications focusing on practical “lessons learned” from investigators in the field.

RECRUITMENT STRATEGIES

Recruitment of an adequate number of study subjects is critical to the successful completion of a clinical trial. Ideally, participants should be enrolled at a constant rate to minimize uneven or excessive staff workloads



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6 Design Considerations: Recruitment and Retention T his chapter explores the influence of recruitment and retention on trial design and conduct. As discussed in Chapter 2, late-stage bio- medical HIV prevention trials require investigators to enroll several hundred to several thousand participants at one or multiple sites, and often follow them for several years. A slow accrual rate or poor retention of trial participants may result in underpowered or biased results. To ensure confidence in trial outcomes, it is essential for investigators to meet the study’s accrual goals and maximize participant retention. Yet meeting each of these goals can be challenging in resource-poor settings with limited infrastructure and highly mobile and diverse populations (Hill, 2004). For example, a recent trial in Tanzania evaluating herpes simplex virus (HSV-2) suppression to reduce HIV infection reported a retention rate of only 60 percent (Watson-Jones et al., 2007). Despite the critical threat that inadequate recruitment and retention pose to trial validity, there is little empirical data on the effectiveness of alternative recruitment and retention strategies (Lovato et al., 1997; Mapstone et al., 2007; Robinson et al., 2007; Villacorta et al., 2007). Thus, most of what the committee describes below is drawn from publications focusing on practical “lessons learned” from investigators in the field. RECRUITMENT STRATEGIES Recruitment of an adequate number of study subjects is critical to the successful completion of a clinical trial. Ideally, participants should be enrolled at a constant rate to minimize uneven or excessive staff workloads 

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 DESIGN CONSIDERATIONS: RECRUITMENT AND RETENTION and to maintain study power during the follow-up period (Lovato et al., 1997). A slowly accruing trial can prolong the evaluation of a product and thus delay its public heath impact if it is shown to be efficacious. Participants in HIV prevention trials enroll for a variety of reasons. Reviews have found that people enroll in HIV/AIDS trial for altruistic reasons more than any other disease area (Lovato et al., 1997; Tharawan et al., 2001). Other common reasons for enrolling include access to HIV education, health care services, contraception (which may not be readably accessible in the community), and for financial incentives (Mills et al., 2006; Tolley and Severy, 2006). In some trials, people say they want to enroll because they believe the product or program will personally protect them against HIV. This underscores the need for additional education about the placebo arm and that the test product has unknown efficacy. Individuals have also cited a number of reasons why they opt not to enroll in HIV prevention trials (Miller et al., 2004; Mills et al., 2006; Newman and Chakrapani, 2006; Suhadev et al., 2006; Tolley and Severy, 2006). Examples include • fears about contracting HIV from the intervention, • potential side effects, • opposition of family or community members, • fear of discrimination or stigma or being perceived as HIV-infected, • lack of convenient clinic hours or transportation to clinic, • fear or dislike of routine procedures (blood draws, pelvic exams), • migration for work or family; possibility of receiving a placebo, • appearing to distrust ones partners, and • distrust of researchers. Understanding the benefits and barriers of participation is important in identifying potential recruitment strategies and areas for education. The committee identified two systematic reviews of recruitment strate- gies (Lovato et al., 1997; Mapstone et al., 2007). Mapstone and colleagues (2007) conducted a review of all randomized and quasi-randomized con- trolled trials of methods to increase recruitment in research studies. Of the 15 studies that met the criteria for inclusion, five broad types of recruitment strategies were identified. In pre-warning strategies, participants were sent information about the study prior to being approached about enrollment. Extra information strategies provided additional information about the study and discussed the benefits to participation and risks of the disease with the person. Study design strategies examined the impact of study design changes (e.g., having a placebo arm) on participation. Consent change strategies examined how change in the informed consent process affected recruitment. Finally, financial incentive strategies were used. All

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0 METHODOLOGICAL CHALLENGES IN HIV PREVENTION TRIALS of the recruitment strategies targeted research participants; no recruitment strategies were targeted at the researcher or ethics committee levels. They found that trials using financial incentives, an additional questionnaire at the enrollment invitation, and providing information about treatment on the consent form were effective. However, due to the heterogeneity of the studies, the authors were unable to quantify the effect of specific strategies on overall participation. They recommend that funders and researchers include evaluation of recruitment strategies in future research studies. Lovato and colleagues (1997) conducted a qualitative evaluation of recruitment strategies used in clinical prevention and treatment trials across numerous disease areas and published through 1995. The authors found that the most commonly cited reasons for recruitment problems were inad- equate planning and monitoring, overestimating the number of participants from a single source, and lack of flexibility or inability to change plans quickly when recruitment strategies failed (Lovato et al., 1997). The review also found that while some trials managed to adhere to the original budget and timeline for recruitment, often investigators underestimated the costs and time needed for recruitment upfront and required time extensions or excessive effort to meet the accrual targets (Lovato et al., 1997). Based on their review, Lovato and colleagues (1997) identified several key strategies for successful planning and management: (1) establishing an overall recruitment plan including pilot studies of strategies, (2) intensively monitoring that plan and shifting strategies when necessary, and (3) hiring high-quality staff. These are briefly reviewed below. • Establishing an Overall Recruitment Plan: Studies with successful recruitment strategies have sufficient time to plan, establish community awareness and education, and make personal contacts (Lovato et al., 1997). Pilot studies are a critical aspect of this planning process and can help iden- tify the length of the enrollment period, the number of clinical sites, and financial commitments (Lovato et al., 1997). Pilot studies are important to understand individuals’ potential willingness to participate in the trial, iden- tify barriers and benefits to participation, and to test specific recruitment strategies (see Chapter 8 for discussion of pretrial research). Such studies have been widely used in the HIV vaccine field and have helped investiga- tors select trial sites and populations and specific retention strategies (see, for example, Dhalla et al., 2007, for a recent review). In addition, inves- tigators should assess local and community beliefs and perceptions about risk behavior, HIV, and clinical research as these can affect community acceptance of clinical trials as well as recruitment and retention strategies (Tolley and Severy, 2006). Understanding these factors can help identify trial design options and education strategies that can mitigate some of the perceived barriers to participation. In planning a trial, participating sites should also be encouraged to

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 DESIGN CONSIDERATIONS: RECRUITMENT AND RETENTION discuss the eligibility requirements and study design with the community to assess the likely screening-to-enrollment ratio that they might realistically expect. The higher the screening-to-enrollment ratio, the more resources are needed to achieve the desired sample size. Regions with high rates of HIV incidence often have high rates of HIV prevalence, so study staff may need to screen many individuals to identify enough eligible uninfected partici- pants, thus increasing the cost of the trial. • Monitoring Accrual: Continuous monitoring of recruitment strate- gies and enrollment targets is important for identifying areas for improve- ment and modifying recruitment strategies when needed. If successful recruitment strategies are identified early in the process, more effort can be shifted to those strategies. Furthermore, timely and accurate recruitment monitoring is essential in informing decisions about whether to extend the enrollment period or to add enrollment targets to other sites in order to meet the sample size goals (Lovato et al., 1997). Data tracking systems (e.g., phone logs, interview outcome logs, schedules) are critical for recruitment staff (Lovato et al., 1997). This can be especially important when there is a high screening–to-enrollment ratio. The actual ratio should also be moni- tored during the enrollment period of the trial. If the ratio is higher than expected, this might indicate whether the eligibility requirements may be too restrictive or whether there is some aspect of the trial that causes some eligible subjects to choose to not enroll. • Staffing: Studies repeatedly cite having high-quality staff as the key to successful recruitment efforts (Lovato et al., 1997; Hill, 2004; Robinson et al., 2007). Having a recruiting coordinator who is responsible for recruitment and who works closely with the principal investigator, data coordinator, and clinic manager in planning strategies can help build suc- cess. Laying out recruitment plans well in advance and identifying ways to quickly replace ineffective strategies is important. Ensuring communication across clinic sites and with other clinical trials in the area is important in identifying successful strategies and identifying problems (Lovato et al., 1997). Characteristics of effective staff that have been identified include being flexible, positive, proactive, and having strong problem-solving skills. Volunteer staff (for example, current participants or participants in other trials) can also be extremely useful in recruiting during clinical trial and in helping to maintain visits during follow-up portion of a trial (Lovato et al., 1997). RETENTION STRATEGIES Efforts to maximize retention should begin with enrollment and con- tinue throughout the trial. Higher-than-anticipated loss of participants to follow-up (LFU, see Chapters 2 and 9) may result in an underpowered trial,

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 METHODOLOGICAL CHALLENGES IN HIV PREVENTION TRIALS and distorted statistical inferences about the effects of the intervention. When losses are “noninformative” in the sense that the HIV infection risk of those who drop out of the study is the same as those who remain in fol- low-up, LFUs will not distort either estimates of cumulative HIV infection rates or comparisons of HIV infection risk between intervention arms, but LFUs will reduce the power of the study to detect an intervention effect (Lagakos et al., 1990). Such a loss of power can be addressed by increas- ing the planned size of the trial to account for anticipated rates of loss to follow-up (Chapter 2). When losses to follow-up are not “noninformative,” estimates of cumulative HIV infection and comparisons between interven- tion arms can be biased and thus not correctable by increasing the sample size of the trial. There is no threshold LFU rate above which a trial’s results become uninterpretable. However, in HIV prevention trials, where only a small percentage (often less than 15 percent) of participants become HIV infected during the trial, striving to keep the cumulative number of LFUs that could be informative below this number is prudent, especially if the LFU rates between the intervention arms might differ. Examples of factors that might affect retention include loss of interest in the study, conflicts in scheduling visits, transportation issues, site loca- tion, poor health, familial obligations, financial difficulties, conflicts with jobs, requirements to forego pregnancy throughout the trial, stringent instructions to adhere to study products, mistrust of trial staff or fear a breach of confidentiality, or stigma associated with an HIV-related study (Coday et al., 2005; Mills et al., 2006; Tolley and Severy, 2006). Investigators and others have also raised concern about whether trials with an unblinded arm would have differential rates of retention across the arms. This situation arose in the recent MIRA diaphragm trial, where par- ticipants in the control arm did not have access to the diaphragm plus gel. Investigators were concerned that more women in the control arm than in the intervention arm would drop out of the study. However, dropout rates were low and similar in the intervention and control arms (6 percent and 5 percent, respectively) (Padian et al., 2007). Researchers have published a number of reviews highlighting promising retention strategies (Hunt and White, 1998; McKenzie et al., 1999; Coday et al., 2005; Robinson et al., 2007; Tansey et al., 2007). As noted, most of these reviews report on lessons learned or identify a common theme among those studies with high rates of retention, but few strategies have been empirically tested. Many of the reviews identify similar themes. However, none were able to correlate specific retention strategies with successful retention rates in trials. Thus, it is unclear which retention strategies work best for whom and under what conditions. First, Hunt and White (1998) conducted a review of four U.S.-based

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 DESIGN CONSIDERATIONS: RECRUITMENT AND RETENTION longitudinal observational cohort studies that provided sufficient infor- mation on their procedures to maximize retention. They identified four successful retention strategies: (1) collaborating with community-based organizations, (2) creating effective organizational structures and manage- ment, (3) selecting and training motivated field staff, and (4) offering inter- ventions that encourage participants to remain involved (Leonard et al., 2003). They found that successful retention requires motivational systems designed to engage and reward individuals at all levels of the trial including project managers and field staff, participants, and community organizations (Leonard et al., 2003). In a second review, McKenzie and colleagues (1999) reviewed methods for tracking and follow-up in 15 studies of marginalized populations. They found that the following procedures are helpful in tracking and following participants: collection of contact information, thorough organization of tracking efforts, staff training and support, use of phone and mail follow- up, use of incentives, establishing rapport with participants, assurance of confidentiality, use of agency tracking and field tracking, and attention to safety concerns. However, none of the studies included in the McKenzie et al. (1999) review were from developing countries. Recent studies show that investigators can achieve retention rates of 84 percent or more in marginalized or “hard to reach” populations over long follow-up periods in resource poor countries (see, for example, Padian et al., 2007; Villacorta et al., 2007), but that these may require different procedures. Tracking individuals in resource-poor settings can be costly and difficult because populations are highly mobile and infrastructure is poor, and formal address systems and population records do not exist (Hill, 2004; Villacorta et al., 2007). A review of 13 studies in developing countries reveals that although tracking participants can be costly, it can reduce attrition up to 45 percent (Hill, 2004). Tracking can be effective if (1) procedures for collecting information on participants’ whereabouts are locally appropriate, well planned, and involve the community; and (2) tracking occurs at regular intervals, and interviewers are well trained, supervised, and motivated (Hill, 2004). Some trials have relied on maps of participants’ homes—often drawn by participants, sometimes with the help of other community members (Hill, 2004; Watadzaushe, 2007). Soliciting information on a network of “anchoring” friends or family may also help staff members track participants, although they must be careful to maintain participant confidentiality when contacting these sources (Leonard et al., 2003). In some settings, tracking information may prove difficult to collect and other strategies may be needed. For example, a study with socially margin- alized young adults in Peru retained 84 percent of participants after 2 years,

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 METHODOLOGICAL CHALLENGES IN HIV PREVENTION TRIALS even though only 26 percent of the population supplied complete locator information (telephone, address, and names of two friends) (Villacorta et al., 2007). Project staff utilized novel retention strategies because traditional locator information was often unavailable or unreadable. These strategies included conducting preliminary ethnographic research to identify behavior or target groups, methods for developing strong bonds with project staff and participants outside the study setting, and methods to enhance partici- pants’ attitudes about the study. Although low-tech, this strategy was labor intensive and may be difficult to replicate (Villacorta et al., 2007). In some instances, a study participant may become incarcerated, in which case it may be difficult or impossible to continue to follow and evaluate her or him as specified in the study protocol. This is sometimes a problem when working with study populations of commercial sex workers or injecting drug users. Coday and colleagues (2005) reviewed strategies for retaining study participants in behavioral intervention trials and identified 61 strategies grouped into eight themes: • Emphasizing the benefits of participation • Minimizing respondent burden and giving control to participants • Providing incentives and tokens of appreciation • Giving tangible support (e.g., transportation expenses) • Being patient and persistent • Being flexible • Enlisting the support of others and providing social support • Maintaining a good tracking system Among these, provision of incentives was highly rated as an effective retention strategy. However, there has been considerable debate about giving people financial rewards to participate in research (Coday et al., 2005). For example, during the committee site visit to South Africa, trial staff noted that the government’s policy of giving a flat 150 rands per visit (not adjusted for location) may be overly influential in rural areas where income is quite low, but insufficient in some high-cost urban areas. Trials with vulnerable populations must ensure that participants do not perceive incentives that are unduly influential, and local institutional review boards (IRBs) must deem them appropriate. The review also discussed retention strategies in the context of an ecological model, which recognizes the influence of multiple factors from an interpersonal, intrapersonal, institutional, community, and policy level. They found that few retention strategies have focused on factors external to the participant that may enhance or detract from study participation

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 DESIGN CONSIDERATIONS: RECRUITMENT AND RETENTION and suggest future studies consider retention strategies targeting external factors. Tansey and colleagues (2007) examined review articles and longitudinal studies that focused on practical and clinically relevant attrition lower- ing strategies. They identified eight narrative reviews that suggested three categories of promising retention strategies. The first theme is respecting patients’ ideas and time. They emphasized that developing a positive rap- port with study subjects early in the study process (when most participants drop out) was essential. Similar to other reviews, this study identified the importance of collecting comprehensive tracking information at the first visit and updating it frequently. Persistence in follow-up, particularly early on was important. In addition, they identified study personnel as a critical component of effective retention. Key strategies included extensive training of staff, adequate staff support, selection of enthusiastic staff, and frequent meetings to reduce isolation often felt by field workers. Finally, Robinson and colleagues (2007) recently conducted a system- atic review of the literature that included all studies through 2005 that described retention strategies for in-person follow-up and included reten- tion rates. Of 21 studies that met these criteria, the authors identified 368 retention strategies which they grouped into 12 themes (see Table 6-1 for details). Similar to other reviewers, the authors were unable to conduct quantitative analyses or associate the types of strategies most effective in various target populations given the heterogeneity of studies included in their review. The authors conclude that more research is needed to explicitly evaluate the effectiveness of alternative retention and recruitment strate- gies. In addition, they encourage researchers to report their experiences with retention in actual trials and recommend adopting standard reporting methods for retention. Overall, investigators and sponsors should anticipate that maintaining timely accrual and high retention rates will be labor intensive and costly throughout a trial. However, these are necessary to maintain internal and external validity. Successful recruitment and retention will require the use of multiple strategies and incentives, the ability to rapidly change procedures when they are not working, and persistence and innovation among staff.

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 METHODOLOGICAL CHALLENGES IN HIV PREVENTION TRIALS TABLE 6-1 Retention Strategy Themes from Robinson, 2007 Theme Description Examples Community involvement Involve community in Present pilot project idea study design, recruitment, to church leadership and and retention. congregation. Create community advisor panel and consult with panel for recommendations regarding protocol and participation. Study identity Create study identity for Create a project identity participants. by using similar colors and fonts on all study materials. Give participants a t-shirt printed with study logo. Study personnel Characteristics, training, Assign one primary clinician and management of study to each participant. personnel. Encourage study personnel to show empathy toward subject’s personal situation in scheduling appointments/cancellations. Study description Explain study Inform subjects that they requirements and details, will be followed over time including potential and specify the timetable benefits and risks, to and the methods that will participants. be used to locate them. Offer a copy of a newspaper article or study brochure to each participant. Contact and scheduling Use systematic method Mail a newsletter to methods for patient contact, participants that includes appointment scheduling, a message from PI, photos and cohort retention of project staff, and monitoring. preliminary findings. Obtain multiple contacts for each participant, including two contacts not residing with the participant. Reminders Provide reminders about Mail reminder postcards appointments and study to participants one week participation. before appointment. Visit in-patients before discharge to remind them of out-patient follow-up plan.

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 DESIGN CONSIDERATIONS: RECRUITMENT AND RETENTION TABLE 6-1 Continued Theme Description Examples Visit characteristics Minimize participant Offer flexible clinic burden through appointments (early characteristics and morning, evenings, and procedures of follow-up weekends). study clinic. Provide background music for restful atmosphere in clinic. Benefits of study Provide benefits to Provide free annual physical participants and families examination. that are directly related to Form educational and the nature of study. support groups for families and patients. Financial incentives Provide financial Provide payment to families incentives or payment. in control group (20USD/ visit/four visits). Provide pharmacy gift certificate to participant at first follow-up visit ($25). Reimbursement Provide reimbursement for Provide taxi fare or have research-related expenses staff member pick up study or tangible support to participants. facilitate participation. Provide child care during visit. Nonfinancial incentives Provide nonfinancial Provide an inexpensive incentives or tokens of token of appreciation (e.g., appreciation. coffee mug, pen, refrigerator magnet) to participant at each visit. Host holiday parties for study participants. Special tracking methods Methods of tracking or Conduct clinic and street dealing with hard-to-find outreach for lost to follow- or difficult participants. up participants. Identify and address obstacles hindering participation for problem patients. SOURCE: This table was published in the Journal of Clinical Epidemiology, Vol 60 (8), Robinson, K. A., C. R. Dennison, D. M. Wayman, P. J. Pronovost, and D. M. Needham, Systematic review identifies number of strategies important for retaining study participants, 757-765, Copyright Elsevier (2007).

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 METHODOLOGICAL CHALLENGES IN HIV PREVENTION TRIALS Recommendation 6-1: Investigators should conduct pretrial research to assess the community and individuals’ interest in the trial, to pilot test recruitment and retention strategies, and to set a realistic timeline and resource needs for the enrollment period and for retention. Recommendation 6-2: Because of the loss in study power that can result from inadequate accrual and because the potential biases result- ing from losses to follow-up cannot be avoided simply by increasing sample size, investigators should place a high priority on developing effective strategies to achieve accrual rate goals and to minimize losses to follow-up. Specifically, investigators should do the following: • Develop a detailed and multifaceted plan for retaining enrolled participants before beginning a study for systematically and frequently monitoring the results, and for modifying the plan if strategies are not working. • Collect as much detailed tracking information as possible on participants. • Develop systems to engage, train, and reward staff for building trust and accountability with participants and within the community, and for meeting recruitment and retention targets. Recommendation 6-3: Funders and investigators should include evalu- ations of the effectiveness of recruitment and retention strategies in future research plans. REFERENCES Coday, M., C. Boutin-Foster, T. Goldman Sher, J. Tennant, M. L. Greaney, S. D. Saunders, and G. W. Somes. 2005. Strategies for retaining study participants in behavioral interven- tion trials: Retention experiences of the NIH Behavior Change Consortium. Annals of Behavioral Medicine 29(Suppl):55-65. Dhalla, S., R. Woods, S. A. Strathdee, D. M. Patrick, and R. S. Hogg. 2007. HIV vaccine preparedness studies in the organization for economic co-operation and development (OECD) countries. AIDS Care 19(9):1118-1127. Hill, Z. 2004. Reducing attrition in panel studies in developing countries. International Jour- nal of Epidemiology 33(3):493-498. Hunt, J. R., and E. White. 1998. Retaining and tracking cohort study members. Epidemiologic Review 20(1):57-70. Lagakos, S. W., L. L. Lim, and J. M. Robins. 1990. Adjusting for early treatment termination in comparative clinical trials. Statistics in Medicine 9(12):1417-1424. Leonard, N. R., P. Lester, M. J. Rotheram-Borus, K. Mattes, M. Gwadz, and B. Ferns. 2003. Successful recruitment and retention of participants in longitudinal behavioral research. AIDS Education and Prevention 15(3):269-281.

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 DESIGN CONSIDERATIONS: RECRUITMENT AND RETENTION Lovato, L. C., K. Hill, S. Hertert, D. B. Hunninghake, and J. L. Probstfield. 1997. Recruitment for controlled clinical trials: Literature summary and annotated bibliography. Controlled Clinical Trials 18(4):328-352. Mapstone, J., D. Elbourne, and I. Roberts. 2007. Strategies to improve recruitment to re- search studies (review). Cochrane Database of Systematic Reviews Issue 2, Art. No.: MR000013. DOI: 10.1002/14651858.MR000013.pub3. McKenzie, M., J. P. Tulsky, H. L. Long, M. Chesney, and A. Moss. 1999. Tracking and follow-up of marginalized populations: A review. Journal of Health Care for the Poor and Underserved 10(4):409-429. Miller, L. C., S. T. Murphy, L. F. Clark, M. Hamburger, and J. Moore. 2004. Hierarchical messages for introducing multiple HIV prevention options: Promise and pitfalls. AIDS Education and Prevention 16(6):509-525. Mills, E., S. Nixon, S. Singh, S. Dolma, A. Nayyar, and S. Kapoor. 2006. Enrolling women into HIV preventive vaccine trials: An ethical imperative but a logistical challenge. PLoS Medicine 3(3):e94. Newman, P. A., and V. Chakrapani. 2006. Methodological and ethical challenges in research with men who have sex with men in Chennai, India. Fairfax, VA: Society for Social Work and Research. Padian, N., A. van der Straten, G. Ramjee, T. Chipato, G. de Bruyn, K. Blanchard, S. Shiboski, E. Montgomery, H. Fancher, H. Cheng, M. Rosenblum, M. van der Loan, N. Jewell, J. McIntyre, and The MIRA Team. 2007. Diaphragm and lubricant gel for prevention of HIV acquisition in southern African women: A randomized controlled trial. Lancet 370:251-261. Robinson, K. A., C. R. Dennison, D. M. Wayman, P. J. Pronovost, and D. M. Needham. 2007. Systematic review identifies number of strategies important for retaining study participants. Journal of Clinical Epidemiology 60(8):757-765. Suhadev, M., A. M. Nyamathi, S. Swaminathan, P. Venkatesan, M. Raja Sakthivel, R. Shenbagavalli, A. Suresh, and J. L. Fahey. 2006. A pilot study on willingness to participate in future preventive HIV vaccine trials. Indian Journal of Medical Research 124(6):631-640. Tansey, C. M., A. L. Matté, D. Needham, and M. S. Herridge. 2007. Review of retention strategies in longitudinal studies and application to follow-up of ICU survivors. Intensive Care Medicine 33:2051-2057. Tharawan, K., C. Manopaiboon, C. Ellertson, K. Limpakarnjanarat, S. Chaikummao, P. H. Kilmarx, K. Blanchard, C. Coggins, T. D. Mastro, and C. Elias. 2001. Women’s willingness to participate in microbicide trials in northern Thailand. Journal of Acquired Immune Deficiency Syndromes 28(2):180-186. Tolley, E. E., and L. J. Severy. 2006. Integrating behavioral and social science research into microbicide clinical trials: Challenges and opportunities. American Journal of Public Health 96(1):79-83. Villacorta, V., S. Kegeles, J. Galea, K. A. Konda, J. P. Cuba, C. F. Palacios, and T. J. Coates. 2007. Innovative approaches to cohort retention in a community-based HIV/STI preven- tion trial for socially marginalized Peruvian young adults. Clinical Trials 4(1):32-41. Watadzaushe, C. 2007. High cohort retention in a phase III trial of the diaphragm and lu- bricant gel in southern Africa. Paper presented at International AIDS Society conference 2007, Sydney, Australia. Watson-Jones, D., M. Rusizoka, H. Weiss, K. Mugeye, K. Baisley, J. Changalucha, D. Everett, C. Tanton, T. Clayton, D. Ross, and R. Hayes. 2007. Impact of HSV- suppressive therapy on HIV incidence in HSV- seropositive women: A randomised controlled trial in Tanzania. Paper read at Fourth International AIDS Society Conference on HIV Patho- genesis, Treatment and Prevention, Sydney, Australia.