A new Bayesian joint model for longitudinal count data with many zeros, intermittent missingness, and dropout with applications to HIV prevention trials.

In longitudinal clinical trials, it is common that subjects may permanently withdraw from the study (dropout), or return to the study after missing one or more visits (intermittent missingness). It is also routinely encountered in HIV prevention clinical trials that there is a large proportion of zeros in count response data. In this paper, a sequential multinomial model is adopted for dropout and subsequently a conditional model is constructed for intermittent missingness. The new model captures the complex structure of missingness and incorporates dropout and intermittent missingness simultaneously. The model also allows us to easily compute the predictive probabilities of different missing data patterns. A zero-inflated Poisson mixed-effects regression model is assumed for the longitudinal count response data. We also propose an approach to assess the overall treatment effects under the zero-inflated Poisson model. We further show that the joint posterior distribution is improper if uniform priors are specified for the regression coefficients under the proposed model. Variations of the g-prior, Jeffreys prior, and maximally dispersed normal prior are thus established as remedies for the improper posterior distribution. An efficient Gibbs sampling algorithm is developed using a hierarchical centering technique. A modified logarithm of the pseudomarginal likelihood and a concordance based area under the curve criterion are used to compare the models under different missing data mechanisms. We then conduct an extensive simulation study to investigate the empirical performance of the proposed methods and further illustrate the methods using real data from an HIV prevention clinical trial.

60 Minutes for health: examining the feasibility and acceptability of a low-resource behavioral intervention designed to promote retention in HIV care.

Sustained retention in HIV medical care is a key health behavior for the long-term health of people living with HIV (PLWH). Approximately 60% of PLWH in the U.S. are poorly retained in HIV care, yet to date, the few available evidence-based retention-promoting interventions are resource and time intensive to implement. The current study describes the feasibility and acceptability of a theory-based retention-promoting intervention designed to meet the needs of a busy clinical care setting. 60 Minutes for Health reflects a low-resource single-session intervention, implemented by a health educator, to PLWH who have had a recent gap in care (≥6-months) in the past 18-months. Intervention content was informed by a situated application of the Information Motivation Behavioral Skills Model and delivered using a Motivational Interviewing-based format. The intervention uses a workbook to guide a series of activities that: (1) Identify and reduce misinformation guiding HIV care attendance. (2) Enhance motivation to maintain care via personal health goals. (3) Build skills for coping with emotional distress related to living with HIV. (4) Increase self-efficacy for navigating the logistics of maintaining care amidst competing priorities. A small feasibility pilot of this intervention protocol was conducted to assess its potential to improve retention in care and to obtain estimates for a larger-scale efficacy trial. Participants were randomized to the 60-minute intervention session (n = 8), or a theory-based time-and-attention control session focused on diet and nutrition (n = 8). Medical records were abstracted to evaluate changes in participants' retention in care status at 12- and 24-months post-intervention. Findings suggest the intervention is both feasible and acceptable to implement with poorly retained PLWH in a clinic setting. Post-intervention a larger proportion of intervention participants were retained in care (12-months: 87.5%, 24-months: 62.5%), compared control participants (12-months: 50.0%, 24-months: 25.0%). Future work should aim to evaluate a larger-scale efficacy trial.

Bayesian Modeling and Inference for Nonignorably Missing Longitudinal Binary Response Data with Applications to HIV Prevention Trials.

Missing data are frequently encountered in longitudinal clinical trials. To better monitor and understand the progress over time, one must handle the missing data appropriately and examine whether the missing data mechanism is ignorable or nonignorable. In this article, we develop a new probit model for longitudinal binary response data. It resolves a challenging issue for estimating the variance of the random effects, and substantially improves the convergence and mixing of the Gibbs sampling algorithm. We show that when improper uniform priors are specified for the regression coefficients of the joint multinomial model via a sequence of one-dimensional conditional distributions for the missing data indicators under nonignorable missingness, the joint posterior distribution is improper. A variation of Jeffreys prior is thus established as a remedy for the improper posterior distribution. In addition, an efficient Gibbs sampling algorithm is developed using a collapsing technique. Two model assessment criteria, the deviance information criterion (DIC) and the logarithm of the pseudomarginal likelihood (LPML), are used to guide the choices of prior specifications and to compare the models under different missing data mechanisms. We report on extensive simulations conducted to investigate the empirical performance of the proposed methods. The proposed methodology is further illustrated using data from an HIV prevention clinical trial.

Exclusive breast-feeding promotion among HIV-infected women in South Africa: an Information-Motivation-Behavioural Skills model-based pilot intervention.

OBJECTIVE: Exclusive breast-feeding (EBF) provides optimal nutrition for infants and mothers. The practice of EBF while adhering to antiretroviral medication decreases the risk of mother-to-child transmission of HIV from approximately 25 % to less than 5 %. Thus the WHO recommends EBF for the first 6 months among HIV-infected women living in resource-limited settings; however, EBF rates remain low. In the present study our aim was to design and implement a pilot intervention promoting EBF among HIV-infected women. DESIGN: The Information-Motivation-Behavioural Skills (IMB) model was applied in a brief motivational interviewing counselling session that was tested in a small randomized controlled trial. SETTING: Pietermaritzburg, South Africa, at two comparable rural public health service clinics. SUBJECTS: Sixty-eight HIV-infected women in their third trimester were enrolled and completed baseline interviews between June and August 2014. Those randomized to the intervention arm received the IMB-based pilot intervention directly following baseline interviews. Follow-up interviews occurred at 6 weeks postpartum. RESULTS: While not significantly different between trial arms, high rates of intention and practice of EBF at 6-week follow-up were reported. Findings showed high levels of self-efficacy being significantly predictive of breast-feeding initiation and duration regardless of intervention arm. CONCLUSIONS: Future research must account for breast-feeding self-efficacy on sustaining breast-feeding behaviour and leverage strategies to enhance self-efficacy in supportive interventions. Supporting breast-feeding behaviour through programmes that include both individual-level and multi-systems components targeting the role of health-care providers, family and community may create environments that value and support EBF behaviour.

HIV transmission risk behavior among HIV-positive patients receiving antiretroviral therapy in KwaZulu-Natal, South Africa.

The aim of this investigation was to identify factors associated with HIV transmission risk behavior among HIV-positive women and men receiving antiretroviral therapy (ART) in KwaZulu-Natal, South Africa. Across 16 clinics, 1,890 HIV+ patients on ART completed a risk-focused audio computer-assisted self-interview upon enrolling in a prevention-with-positives intervention trial. Results demonstrated that 62 % of HIV-positive patients' recent unprotected sexual acts involved HIV-negative or HIV status unknown partners. For HIV-positive women, multivariable correlates of unprotected sex with HIV-negative or HIV status unknown partners were indicative of poor HIV prevention-related information and of sexual partnership-associated behavioral skills barriers. For HIV-positive men, multivariable correlates represented motivational barriers, characterized by negative condom attitudes and the experience of depressive symptomatology, as well as possible underlying information deficits. Findings suggest that interventions addressing gender-specific and culturally-relevant information, motivation, and behavioral skills barriers could help reduce HIV transmission risk behavior among HIV-positive South Africans.

HIV stigma and unprotected sex among PLWH in KwaZulu-Natal, South Africa: a longitudinal exploration of mediating mechanisms.

Social and structural factors including HIV stigma are theorized to drive global disparities in HIV prevalence. This study tests whether HIV self-stigma, or experiences of stigma at the individual level, is associated with engagement in unprotected sex among people living with HIV (PLWH) in KwaZulu-Natal, South Africa, where 37.4% of adults are living with HIV compared with 0.8% worldwide. It further explores whether depressive symptoms, HIV status disclosure to sex partners, and/or condom use attitudes mediate potential associations between HIV self-stigma and unprotected sex. Participants, including 924 PLWH, were recruited from primary care clinics and completed baseline, 6-, 12-, and 18-month survey assessments between 2008 and 2011. Hierarchical linear modeling analyses were used to examine longitudinal within-subjects associations between HIV self-stigma, mediators, and unprotected sex with both HIV-negative/unknown and HIV-positive partners. Results demonstrate that HIV self-stigma was prospectively associated with greater likelihood of unprotected sex with HIV-negative/unknown partners. None of the variables explored significantly mediated this association. HIV self-stigma was also prospectively associated with greater likelihood of unprotected sex with HIV-positive partners via the mediators of greater depressive symptoms and more negative condom use attitudes. The current study suggests that HIV self-stigma undermines HIV secondary prevention and care efforts among PLWH in KwaZulu-Natal. It is therefore critical to address HIV stigma at the social/structural level to reduce HIV self-stigma at the individual level and ultimately curb global disparities in HIV prevalence. In the absence of widespread social/structural change, interventions that treat depressive symptoms and encourage more positive condom use attitudes despite the existence of HIV stigma may buffer associations between HIV self-stigma and unprotected sex with HIV-positive partners among PLWH in KwaZulu-Natal.

Information, motivation, and behavioral skills for early pre-ART engagement in HIV care among patients entering clinical care in KwaZulu-Natal, South Africa.

Little is known regarding factors implicated in early engagement and retention in HIV care among individuals not yet eligible for antiretroviral therapy (pre-ART) in sub-Saharan Africa. Identifying such factors is critical for supporting retention in pre-ART clinical care to ensure timely ART initiation and optimize long-term health outcomes. We assessed patients' pre-ART HIV care-related information, motivation, and behavioral skills among newly diagnosed ART-ineligible patients, initiating care in KwaZulu-Natal, South Africa. The survey was interviewer-administered to eligible patients, who were aged 18 years or older, newly entering care (diagnosed within the last six-months), and ineligible for ART (CD4 count > 200 cells/mm(3)) in one of four primary care clinical sites. Self-reported information, motivation, and behavioral skills specific to retention in pre-ART HIV-care were characterized by categorizing responses into those reflecting potential strengths and those reflective of potential deficits. Information, motivation, and behavioral skills deficits sufficiently prevalent in the overall sample (i.e.,≥30% prevalent) were identified as areas in need of specific attention through intervention efforts adapted to the clinic level. Gender-based differences were also evaluated. A total of 288 patients (75% female) completed structured interviews. Across the sample, eight information, eight motivation, and eight behavioral skills deficit areas were identified as sufficiently prevalent to warrant specific targeted attention. Gender differences did not emerge. The deficits in pre-ART HIV care-related information, motivation, and behavioral skills that were identified suggest that efforts to improve accurate information on immune function and HIV disease are needed, as is accurate information regarding HIV treatment and transmission risk prior to ART initiation. Additional efforts to facilitate the development of social support, including positive interactions with clinic staff and decreasing community-level stigma and to decrease structural and resource-depleting demands of HIV care may be particularly valuable to facilitate retention in pre-ART HIV care.

Development and pilot-testing of a hepatitis C reinfection prevention intervention for patients in treatment for hepatitis C infection.

•We developed a two-session behavioral intervention to prevent HCV reinfection.•The intervention was piloted at an OTP and integrated into HCV treatment.•Baseline data showed limited knowledge & application of safer injection practices.•Implementation barriers included logistics and the lack of financial incentive.•Adaptations addressed barriers, yielding a more feasible and acceptable intervention.

Computer-based intervention in HIV clinical care setting improves antiretroviral adherence: the LifeWindows Project.

We evaluated the efficacy of LifeWindows, a theory-based, computer-administered antiretroviral (ARV) therapy adherence support intervention, delivered to HIV + patients at routine clinical care visits. 594 HIV + adults receiving HIV care at five clinics were randomized to intervention or control arms. Intervention vs. control impact in the intent-to-treat sample (including participants whose ARVs had been entirely discontinued, who infrequently attended care, or infrequently used LifeWindows) did not reach significance. Intervention impact in the On Protocol sample (328 intervention and control arm participants whose ARVs were not discontinued, who attended care and were exposed to LifeWindows regularly) was significant. On Protocol intervention vs. control participants achieved significantly higher levels of perfect 3-day ACTG-assessed adherence over time, with sensitivity analyses maintaining this effect down to 70% adherence. This study supports the utility of LifeWindows and illustrates that patients on ARVs who persist in care at clinical care sites can benefit from adherence promotion software.

A network-individual-resource model for HIV prevention.

HIV is transmitted through dyadic exchanges of individuals linked in transitory or permanent networks of varying sizes. A theoretical perspective that bridges key individual level elements with important network elements can be a complementary foundation for developing and implementing HIV interventions with outcomes that are more sustainable over time and have greater dissemination potential. Toward that end, we introduce a Network-Individual-Resource (NIR) model for HIV prevention that recognizes how exchanges of resources between individuals and their networks underlies and sustains HIV-risk behaviors. Individual behavior change for HIV prevention, then, may be dependent on increasing the supportiveness of that individual's relevant networks for such change. Among other implications, an NIR model predicts that the success of prevention efforts depends on whether the prevention efforts (1) prompt behavior changes that can be sustained by the resources the individual or their networks possess; (2) meet individual and network needs and are consistent with the individual's current situation/developmental stage; (3) are trusted and valued; and (4) target high HIV-prevalence networks.

Toward an information-motivation-behavioral skills model of microbicide adherence in clinical trials.

Unless optimal adherence in microbicide clinical trials is ensured, an efficacious microbicide may be rejected after trial completion, or development of a promising microbicide may be stopped, because low adherence rates create the illusion of poor efficacy. We provide a framework with which to conceptualize and improve microbicide adherence in clinical trials, supported by a critical review of the empirical literature. The information-motivation-behavioral skills (IMB) model of microbicide adherence conceptualizes microbicide adherence in clinical trials and highlights factors that can be addressed in behavioral interventions to increase adherence in such trials. This model asserts that microbicide adherence-related information, motivation, and behavioral skills are fundamental determinants of adherent microbicide utilization. Specifically, information consists of objective facts about microbicide use (e.g., administration and dosage) as well as heuristics that facilitate use (e.g., microbicides must be used with all partners). Motivation to adhere consists of attitudes toward personal use of microbicides (e.g., evaluating the consequences of using microbicides as good or pleasant) as well as social norms that support their use (e.g., beliefs that a sexual partner approves use of microbicides). Behavioral skills consist of objective skills necessary for microbicide adherence (e.g., the ability to apply the microbicide correctly and consistently). Empirical evidence concerning microbicide acceptability and adherence to spermicides, medication, and condom use regimens support the utility of this model for understanding and promoting microbicide adherence in clinical trials.

Information-motivation-behavioral skills barriers associated with intentional versus unintentional ARV non-adherence behavior among HIV+ patients in clinical care.

Since the arrival of antiretroviral (ARV) therapy, HIV has become better characterized as a chronic disease rather than a terminal illness, depending in part on one's ability to maintain relatively high levels of adherence. Despite research concerning barriers and facilitators of ARV adherence behavior, relatively little is known about specific challenges faced by HIV-positive persons who report "taking a break" from their ARV medications. The present study employed the Information-Motivation-Behavioral Skills Model of ARV adherence as a framework for understanding adherence-related barriers that may differentiate between non-adherent patients who report "taking a break" versus those who do not report "taking a break" from their ARV medications. A sample of 327 HIV-positive patients who reported less than 100% adherence at study baseline provided data for this research. Participants who reported "taking a break" from their HIV medications without first talking to their healthcare provider were classified as intentionally non-adherent, while those who did not report "taking a break" without first talking with their healthcare provider were classified as unintentionally non-adherent. Analyses examined differences between intentionally versus unintentionally non-adherent patients with respect to demographic characteristics and responses to the adherence-related information, motivation, and behavioral skills questionnaire items. Few differences were observed among the groups on demographics, adherence-related information, or adherence-related motivation; however, significant differences were observed on about half of the adherence-related behavioral skills items. Implications for future research, as well as the design of specific intervention components to reduce intentionally non-adherent behavior, are discussed.

An agenda for advancing the science of implementation of evidence-based HIV prevention interventions.

In the past 25 years, a tremendous amount of time and resources have been committed to developing evidence-based HIV prevention interventions. More recently, there have been noteworthy efforts to develop an infrastructure and related policies to promote the dissemination (i.e., "the targeted distribution of information and intervention materials to a specific public health or clinical practice audience") of evidence-based interventions. Despite these advances, however, we have had comparatively little success in the effective implementation (i.e., "the use of strategies to adopt and integrate evidence-based health interventions and change practice patterns within specific settings") of such interventions in everyday practice or community settings. The objective of the current paper is to highlight select and initial areas of research that are critically needed to advance the state-of-the-science of implementation of HIV prevention interventions in our broader efforts to curb the epidemic worldwide.

The information-motivation-behavioral skills model of ART adherence in a Deep South HIV+ clinic sample.

High levels of adherence to antiretroviral therapy (ART) are critical to the management of HIV, yet many people living with HIV do not achieve these levels. There is a substantial body of literature regarding correlates of adherence to ART, and theory-based multivariate models of ART adherence are emerging. The current study assessed the determinants of adherence behavior postulated by the Information-Motivation-Behavioral Skills model of ART adherence in a sample of 149 HIV-positive patients in Mississippi. Structural equation modeling indicated that ART-related information correlated with personal and social motivation, and the two sub-areas of motivation were not intercorrelated. In this Deep South sample, being better informed, socially supported, and perceiving fewer negative consequences of adherence were independently related to stronger behavioral skills for taking medications, which in turn associated with self-reported adherence. The IMB model of ART adherence appeared to well characterize the complexities of adherence for this sample.

The information-motivation-behavioral skills model of antiretroviral adherence and its applications.

Suboptimal adherence to highly active antiretroviral therapy (HAART) may have serious consequences for HIV patients, and for public health overall. The Information-Motivation-Behavioral Skills (IMB) model of HAART adherence can be used to understand the dynamics of HAART adherence and to intervene with patients to promote more optimal levels of adherence. This article reviews the core hypotheses of the IMB model of HAART adherence and describes available correlational and experimental evaluations of the model, outcomes of adherence intervention trials that applied the model, and IMB model-based interventions that are currently under evaluation. It then explores one potential promising application of the model that uses a protocol originally developed and demonstrated as a structured patient-centered, provider-delivered risk reduction intervention to deliver information, motivation, and behavioral skills-based adherence-promotion strategies. This protocol could be incorporated into clinical practice as a valuable tool in working with patients individually.

A music-based HIV prevention intervention for urban adolescents.

OBJECTIVE: This research examines the process of conducting and evaluating a music-based HIV prevention intervention among urban adolescents, and is informed by the information, motivation, behavioral skills (IMB) model. DESIGN: Musically talented opinion leaders were recruited to write, record, and distribute HIV prevention themed music to their peers to increase HIV prevention motivation, behavioral skills, and behaviors. In this 3-month field experiment, participants were 306 students enrolled in health classes at each of three large multiracial urban high schools (one treatment school; two control schools). MAIN OUTCOME MEASURES: Measures of HIV prevention information, motivation, behavioral skills, and behaviors, both pre- and postintervention. RESULTS AND CONCLUSION: Results indicate that the intervention influenced several aspects of HIV prevention motivation, behavioral skills, and condom use and HIV testing behaviors. This research demonstrates that the incorporation of music into HIV prevention interventions for adolescents has the potential to be effective.

Attitudes toward needle-sharing and HIV transmission risk behavior among HIV+ injection drug users in clinical care.

Risky behavior related to injection drug use accounts for a considerable proportion of incident HIV infection in the United States. Large numbers of injection drug users (IDUs) currently receive antiretroviral therapy in clinical settings and are accessible for risk-reduction interventions to reduce transmission of drug-resistant HIV and spread of HIV to uninfected others. The current study examined attitudes toward needle- or equipment-sharing among 123 HIV-positive IDUs in clinical care in an effort to understand the dynamics of such behavior and to create a basis for clinic-based risk-reduction interventions. Results indicate that at baseline, participants who reported extremely negative attitudes toward needle-sharing were less likely to have shared during the past month than those with less-extreme negative attitudes. Demographic, behavioral, and attitudinal variables were entered into a logistic regression model to examine needle-sharing group membership among HIV-positive IDUs. Being female and having less-extreme negative attitudes toward sharing were independent and significant correlates of sharing behavior. Interventions targeting needle-sharing attitudes deployed within the clinical care setting may be well-positioned to reduce HIV transmission among HIV-positive IDUs.

An information-motivation-behavioral skills (IMB) model-based HIV prevention intervention for truck drivers in India.

The incidence of HIV/AIDS in India is increasing drastically, and truck drivers are seen as critical sources of HIV transmission due to their high rates of unprotected sex with multiple partners. An intervention based on the Information-Motivation-Behavioral Skills (IMB) model was compared to an information-only control condition in a randomized trial. IMB constructs were assessed among 250 male truck drivers immediately prior to and following implementation of the intervention, and sexual and condom use behaviors were assessed approximately 10 months later. The intervention consisted of a single-session group workshop with 5 interactive activities designed to address HIV prevention-related IMB constructs and to motivate condom use. Findings showed mixed support for the effectiveness of the intervention. There was an effect of the IMB intervention on attitudes, norms, behavioral skills, and intentions specific to condom use with marital partners, but no effects on constructs related to non-marital partners. There was some evidence of greater condom use with marital and non-marital partners at behavioral follow-up for participants in the IMB condition, and effects on condom use with marital partners were mediated by changes in IMB constructs. These findings provide initial evidence for the effectiveness of theoretically-based approaches to HIV prevention in India.

Sexual risk behaviour among HIV-positive individuals in clinical care in urban KwaZulu-Natal, South Africa.

We assessed the incidence and predictors of unprotected sex among 152 HIV-positive patients in clinical care in KwaZulu-Natal, South Africa. Nearly 50% were sexually active; 30% of those reported unprotected sex. Alcohol use during sex, reporting forced sex, sex with a perceived HIV-positive partner, and sex with a casual partner predicted more unprotected sex, whereas HIV status disclosure was related to less unprotected sex. These findings highlight the need for linking HIV prevention and care in Africa.

An information-motivation-behavioral skills model of adherence to antiretroviral therapy.

HIV-positive persons who do not maintain consistently high levels of adherence to often complex and toxic highly active antiretroviral therapy (HAART) regimens may experience therapeutic failure and deterioration of health status and may develop multidrug-resistant HIV that can be transmitted to uninfected others. The current analysis conceptualizes social and psychological determinants of adherence to HAART among HIV-positive individuals. The authors propose an information-motivation-behavioral skills (IMB) model of HAART adherence that assumes that adherence-related information, motivation, and behavioral skills are fundamental determinants of adherence to HAART. According to the model, adherence-related information and motivation work through adherence-related behavioral skills to affect adherence to HAART. Empirical support for the IMB model of adherence is presented, and its application in adherence-promotion intervention efforts is discussed.