[Show abstract][Hide abstract] ABSTRACT: In Denmark, the first standalone supervised injecting facility (SIF) opened in Copenhagen's Vesterbro neighborhood on October 1, 2012. The purpose of this study was to assess whether use of services provided by the recently opened SIF was associated with changes in injecting behavior and syringe disposal practices among people who inject drugs (PWID). We hypothesized that risk behaviors (e.g., syringe sharing), and unsafe syringe disposal (e.g., dropping used equipment on the ground) had decreased among PWID utilizing the SIF.
[Show abstract][Hide abstract] ABSTRACT: Racial disparities in clinic attendance may contribute to racial disparities in plasma human immunodeficiency virus type 1 (HIV-1) RNA levels among HIV-positive patients in care. Data from 946 African American and 535 Caucasian patients receiving HIV care at the University of North Carolina Center for AIDS Research HIV clinic between January 1, 1999, and August 1, 2012, were used to estimate the association between African American race and HIV virological suppression (i.e., undetectable HIV-1 RNA) when racial disparities in clinic attendance were lessened. Clinic attendance was measured as the proportion of scheduled clinic appointments attended (i.e., visit adherence) or the proportion of six 4-month intervals with at least 1 attended scheduled clinic appointment (i.e., visit constancy). In analyses accounting for patient characteristics, the risk ratio for achieving suppression when comparing African Americans with Caucasians was 0.91 (95% confidence interval: 0.85, 0.98). Lessening disparities in adherence or constancy lowered disparities in virological suppression by up to 44.4% and 11.1%, respectively. Interventions that lessen disparities in adherence may be more effective in eliminating disparities in suppression than interventions that lessen disparities in constancy. Given that gaps in care were limited to be no more than 2 years for both attendance measures, the impact of lessening disparities in adherence may be overstated.
American journal of epidemiology 05/2014; · 5.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction: Studies examining the use of pre-exposure prophylaxis (PrEP) to prevent HIV transmission among people who inject drugs (PWIDs) have not been adequately summarized. Recently, the Bangkok Tenofovir Study has shown that PrEP may be effective at reducing new HIV infections among this high-risk group. This randomized controlled trial was the first study to specifically examine the efficacy of PrEP among PWIDs. In this review, we present the current state of evidence regarding the use of PrEP to prevent HIV infection in PWID populations, and set an agenda for future research to inform the most effective implementation of PrEP in the context of existing evidence-based HIV prevention strategies. Discussion: Despite positive trial results confirming that PrEP may prevent HIV transmission among PWIDs, there remain many questions regarding the interpretation of these results, as well as obstacles to the implementation of PrEP regimens within highly diverse drug-using communities. Aside from the Bangkok Tenofovir Study, we identified only one other published study that has collected empirical data to inform the use of PrEP among PWIDs. The large gap in research regarding the use and implementation of PrEP for PWIDs signals the need for further research and attention. Conclusions: We recommend that future research efforts focus on elucidating the generalizability of the Bangkok Tenofovir Study results in other injection drug-using populations, examining the willingness of PWIDs to use PrEP in diverse contexts, identifying barriers to adherence to PrEP regimens and determining the most effective ways to implement PrEP programmes within the context of existing evidence-based prevention strategies, including opioid substitution therapy and needle and syringe distribution programmes.
Journal of the International AIDS Society 03/2014; 17(1):18899. · 3.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective
To determine whether HIV status and knowledge of mother-to-child-transmission (MTCT) of HIV are associated with antenatal care (ANC) use.
Data were obtained from the 2011 Ethiopia Demographic and Health Survey among women aged 15–49 years who agreed to HIV testing and who reported giving birth in the preceding five years. The two exposures of interest were HIV status and knowledge of MTCT. Unadjusted and adjusted prevalence ratios for ANC use were estimated by fitting modified Poisson regression models.
Among the 7392 women in the sample, ANC use was lowest among HIV-negative, low MTCT knowledge women (31.6% [95% confidence interval: 28.1–35.1]), and highest among HIV-positive, high knowledge women (81.9% [69.8–94.0%]). ANC use was significantly higher among HIV-positive, high knowledge (adjusted prevalence ratio [APR] = 1.60 [1.32–1.94]) and HIV-negative, high knowledge women (1.37 [1.24–1.51]) compared with HIV-negative, low knowledge women. There was no statistically significant difference in ANC use by HIV status among low knowledge women (1.26 [0.71–2.25]).
HIV-positive women generally had better MTCT knowledge. Among HIV-negative women, the prevalence of ANC use was greater among women with higher knowledge. Increasing MTCT knowledge may facilitate ANC use and in turn may eliminate MTCT.
Journal of Epidemiology and Global Health. 01/2014;
[Show abstract][Hide abstract] ABSTRACT: The causes of poor clinic attendance and incomplete virologic suppression among HIV+ African Americans (AAs) are not well understood. We estimated the effect of at-risk alcohol/drug use and associated treatment on attending scheduled appointments and virologic suppression among 576 HIV+ AA patients in the UAB 1917 Clinic Cohort who contributed 591 interviews to the analysis. At interview, 78% of patients were new to HIV care at UAB, 38% engaged in at-risk alcohol/drug use or received associated treatment in the prior year, while the median (quartiles) age and CD4 count were 36 (28; 46) years and 321 (142; 530) cells/microl, respectively. In the two years after an interview, half of patients had attended at least 82% of appointments while half had achieved virologic suppression for at least 71% of RNA assessments. Compared to patients who did not use or receive treatment, the adjusted risk ratio (aRR) for attending appointments for patients who did use but did not receive treatment was 0.97 (95% confidence limits: 0.92, 1.03). The corresponding aRR for virologic suppression was 0.94 (0.86, 1.03). Compared to patients who did not receive treatment but did use, the aRR for attending appointments for patients who did receive treatment and did use was 0.86 (0.78, 0.95). The corresponding aRR for virologic suppression was 1.07 (0.92, 1.24). Use was negatively associated with attendance and virologic suppression among patients not in treatment. Among users, treatment was negatively associated with attendance yet positively associated with virologic suppression. However, aRR estimates were imprecise.
AIDS research and human retroviruses 12/2013; · 2.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The joint effects of multiple exposures on an outcome are frequently of interest in epidemiologic research. In 2001, Hernán et al (J Am Stat Assoc. 2001;96:440-448) presented methods for estimating the joint effects of multiple time-varying exposures subject to time-varying confounding affected by prior exposure using joint marginal structural models. Nonetheless, the use of these joint models is rare in the applied literature. Minimal uptake of these joint models, in contrast to the now widely used standard marginal structural model, is due in part to a lack of examples demonstrating the method. In this paper, we review the assumptions necessary for unbiased estimation of joint effects as well as the distinction between interaction and effect measure modification. We demonstrate the use of marginal structural models for estimating the joint effects of alcohol consumption and injection drug use on HIV acquisition, using data from 1525 injection drug users in the AIDS Link to Intravenous Experience cohort study. In the joint model, the hazard ratio (HR) for heavy drinking in the absence of any drug injections was 1.58 (95% confidence interval = 0.67-3.73). The HR for any drug injections in the absence of heavy drinking was 1.78 (1.10-2.89). The HR for heavy drinking and any drug injections was 2.45 (1.45-4.12). The P values for multiplicative and additive interaction were 0.7620 and 0.9200, respectively, indicating a lack of departure from effects that multiply or add. We could not rule out interaction on either scale due to imprecision.
[Show abstract][Hide abstract] ABSTRACT: In time-to-event analyses, artificial censoring with correction for induced selection bias using inverse probability-of-censoring weights can be used to 1) examine the natural history of a disease after effective interventions are widely available, 2) correct bias due to noncompliance with fixed or dynamic treatment regimens, and 3) estimate survival in the presence of competing risks. Artificial censoring entails censoring participants when they meet a predefined study criterion, such as exposure to an intervention, failure to comply, or the occurrence of a competing outcome. Inverse probability-of-censoring weights use measured common predictors of the artificial censoring mechanism and the outcome of interest to determine what the survival experience of the artificially censored participants would be had they never been exposed to the intervention, complied with their treatment regimen, or not developed the competing outcome. Even if all common predictors are appropriately measured and taken into account, in the context of small sample size and strong selection bias, inverse probability-of-censoring weights could fail because of violations in assumptions necessary to correct selection bias. The authors used an example from the Multicenter AIDS Cohort Study, 1984-2008, regarding estimation of long-term acquired immunodeficiency syndrome-free survival to demonstrate the impact of violations in necessary assumptions. Approaches to improve correction methods are discussed.
American journal of epidemiology 02/2011; 173(5):569-77. · 5.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: to estimate the effect of alcohol consumption on HIV acquisition while appropriately accounting for confounding by time-varying risk factors.
african-American injection drug users in the AIDS Link to Intravenous Experience cohort study. Participants were recruited and followed with semiannual visits in Baltimore, Maryland between 1988 and 2008.
marginal structural models were used to estimate the effect of alcohol consumption on HIV acquisition.
at entry, 28% of 1525 participants were women with a median (quartiles) age of 37 (32-42) years and 10 (10-12) years of formal education. During follow-up, 155 participants acquired HIV and alcohol consumption was 24, 24, 26, 17, and 9% for 0, 1-5, 6-20, 21-50, and 51-140 drinks per week over the prior 2 years, respectively. In analyses accounting for sociodemographic factors, drug use, and sexual activity, hazard ratios for participants reporting 1-5, 6-20, 21-50, and 51-140 drinks per week in the prior 2 years compared to participants who reported 0 drinks per week were 1.09 (0.60-1.98), 1.18 (0.66-2.09), 1.66 (0.94-2.93), and 2.12 (1.15-3.90), respectively. A trend test indicated a dose-response relationship between alcohol consumption and HIV acquisition (P value for trend = 9.7 × 10).
a dose-response relationship between alcohol consumption and subsequent HIV acquisition is indicated, independent of measured known risk factors.
AIDS (London, England) 01/2011; 25(2):221-8. · 4.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Predictors of study retention and scheduled visit attendance in the University of North Carolina Center for AIDS Research (UNC CFAR) prospective clinical cohort of HIV-infected patients enrolled between 1 January 2001 and 1 January 2008 are reported. At study entry, 1636 participants were 32% female, 58% were African-American, 49% had not received HIV care elsewhere, 71% were receiving or initiated combination antiretroviral therapy, and 26% were diagnosed with AIDS, with median (quartiles) age of 40 (34; 47) years, distance to clinic of 45 (21; 70) miles, HIV-1 RNA of 1396 (200; 26,750) copies/ml, and CD4 of 374 (182; 602) cells/mm(3). Participants contributed a median of 7 (4; 13) scheduled visits and 2.25 (1.0; 3.9) years alive under follow-up. During 6134 person-years of follow-up, 414 participants dropped out and 145 died. Accounting for differences in death by participant characteristics, the 6-year cumulative probability of retention was 67% [95% confidence limits (CL): 65, 70%], with 6.75 (95% CL: 6.13, 7.43) drop outs per 100 person-years. In a multivariable Cox proportional hazards model, retention was higher among participants who were insured, had not received HIV care elsewhere, had controlled HIV viremia, and were living in nonurban areas or proximate to the clinic. In a multivariable modified Poisson regression model that accounted for differences in drop out and death by participant characteristics, visit attendance was higher among older, AIDS-diagnosed, immune compromised, and cART-initiated participants. The UNC CFAR clinical cohort has ample enrollment with retention and visit attendance modestly influenced by factors such as disease severity.
AIDS research and human retroviruses 08/2010; 26(8):875-81. · 2.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Discuss issues related to time-varying exposures using as an example the recently meta-analyzed literature (Baliunas et al. in Int J Public Health, 2009) on alcohol consumption and risk of HIV infection.
Cataloged sources of bias and imprecision in the context of time-varying exposures.
Confounding, selection, or measurement bias may occur when standard regression approaches are used to estimate effects of time-varying exposures. The reviewed literature on alcohol consumption and HIV infection suffer from one or more of these biases.
Detailed prospective data and thoughtful implementation of appropriate statistical methods are needed to obtain unbiased estimates of time-varying exposures, such as alcohol consumption.
International Journal of Public Health 02/2010; 55(3):227-8. · 1.99 Impact Factor