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1.  Methods for Recruiting Men of Color Who Have Sex with Men in Prevention-for-Positives Interventions 
Men who have sex with men (MSM), especially MSM of color, are disproportionately impacted by HIV/AIDS compared to heterosexuals and Caucasians. Nonetheless, fewer sexual and ethnic minorities participate in prevention interventions for people with HIV. We consider recruitment for Positive Connections, a randomized controlled trial comparing unsafe sex prevention interventions primarily for HIV-positive (HIV+) MSM in six US epicenters. One community-based organization (CBO) in each city recruited adult MSM, particularly men of color and HIV+. Recruitment methods included on-line and print advertising, outreach events, health professionals, and social networks. Data on demographics, HIV status, and recruitment method were collected at registration. We tested for differences in registration proportions and attendance rates by recruitment strategy, stratified on race/ethnicity and serostatus. Of the 1,119 registrants, 889 attended the intervention. The sample comprised 41% African American, 18% Latino/Hispanic, and 77% HIV+. Friend referral was reported by the greatest proportion of registrants, particularly among African American (33%) and HIV+ men (25%). Print advertising yielded the largest proportions of non-Hispanic white (27%) and HIV-negative registrants (25%). Registrants recruited on-line were the least likely to attend (45% versus 69% average); this effect was strongest among Latino/Hispanic (27% attendance) and non-Hispanic white men (36%). Retention during the follow-up period did not differ by serostatus, race/ ethnicity, or recruitment method. Differential attendance and retention according to recruitment strategy, serostatus, and racial/ethnic group can inform planning for intervention sample size goals.
PMCID: PMC3691812  PMID: 19731034
Recruitment; Men who have sex with men (MSM); HIV-positive; Minorities
2.  Comparison of substance use and risky sexual behavior among a diverse sample of urban, HIV-positive men who have sex with men 
Journal of addictive diseases  2009;28(3):208-218.
To measure substance use across racial and ethnic subgroups of HIV-positive men who have sex with men (MSM), model associations between drug use and unsafe sex, and characterize users of the substances most strongly associated with risky sexual behavior.
Cross-sectional survey at the pre-intervention time point of the Positive Connections behavioral intervention trial.
HIV-positive men of color who have sex with men living in six US cities.
675 trial participants.
Self-reported drug and alcohol use and sexual behaviors.
We found high prevalence of substance use in this sample, with differences across racial and ethnic groups. Compared to Hispanic, African America, and men of other or mixed races/ethnicities, Caucasian men were most likely to report use of stimulants (30%), methamphetamines (27%), and amyl nitrite inhalants (“poppers”, 46%) with anal sex. African American men reported crack/cocaine use in the highest proportion (38%) among the four groups. While many drugs were individually associated with serodiscordant unprotected anal intercourse (SDUAI), only alcohol quantity and poppers with sex were retained in a multivariate model. More frequent poppers use was associated with more reported instances of SDUAI, adjusted for increased anal sex. Men who used poppers were more likely to be white, have completed more education, and have slightly higher income than non-users. Poppers users also reported lower peer norms and self-efficacy for condom use. In a multiple logistic regression model including these psychosocial factors, only poppers use (vs non-use OR = 2.46, CI: 1.55, 3.94) and condom self-efficacy (1 sd increase on scale OR = .58, CI: .46, .73) were significantly associated with SDUAI.
These results, from a large sample of HIV-positive MSM of color, highlight the HIV transmission importance of drugs used specifically in conjunction with sex.
PMCID: PMC3437600  PMID: 20155589
Homosexuality; Male; Street Drugs; HIV Seropositivity; Sexual Behavior
3.  Multilevel empirical Bayes modeling for improved estimation of toxicant formulations to suppress parasitic sea lamprey in the upper Great Lakes 
Biometrics  2011;67(3):1153-1162.
Estimation of extreme quantal-response statistics, such as the concentration required to kill 99.9% of test subjects (LC99.9), remains a challenge in the presence of multiple covariates and complex study designs. Accurate and precise estimates of the LC99.9 for mixtures of toxicants is critical to ongoing control of a parasitic invasive species, the sea lamprey, in the Laurentian Great Lakes of North America. The toxicity of those chemicals is affected by local and temporal variations in water chemistry, which must be incorporated into the modeling. We develop multilevel empirical Bayes models for data from multiple laboratory studies. Our approach yields more accurate and precise estimation of the LC99.9 compared to alternative models considered. This study demonstrates that properly incorporating hierarchical structure in laboratory data yields better estimates of LC99.9 stream treatment values that are critical to larvae control in the field. In addition, out-of-sample prediction of the results of in situ tests reveals the presence of a latent seasonal effect not manifest in the laboratory studies, suggesting avenues for future study and illustrating the importance of dual consideration of both experimental and observational data.
PMCID: PMC3111860  PMID: 21361894
Lethal concentration/dose; Markov chain Monte Carlo (MCMC); Non-linear model; Quantal-response bioassay
4.  Joint modeling of multiple longitudinal patient-reported outcomes and survival 
Researchers often include patient-reported outcomes (PROs) in Phase III clinical trials to demonstrate the value of treatment from the patient’s perspective. These data are collected as longitudinal repeated measures and are often censored by occurrence of a clinical event that defines a survival time. Hierarchical Bayesian models having latent individual-level trajectories provide a flexible approach to modeling such multiple outcome types simultaneously. We consider the case of many zeros in the longitudinal data motivating a mixture model, and demonstrate several approaches to modeling multiple longitudinal PROs with survival in a cancer clinical trial. These joint models may enhance Phase III analyses and better inform health care decision makers.
PMCID: PMC3212950  PMID: 21830926
cancer; failure time; multivariate analysis; random effects model; repeated measures
5.  Effects of a behavioral intervention to reduce serodiscordant unsafe sex among HIV positive Men who have Sex with Men: The Positive Connections randomized controlled trial study 
Journal of behavioral medicine  2010;33(2):147-158.
Few behavioral interventions have been conducted to reduce high-risk sexual behavior among HIV-positive Men who have Sex with Men (HIV+MSM). Hence, we lack well-proven interventions for this population.
Positive Connections is a randomized controlled trial (n=675 HIV+MSM) comparing the effects of two sexual health seminars – for HIV+MSM and all MSM – with a contrast prevention video arm. Baseline, 6-, 12- and 18-month follow-up surveys assessed important psychosexual variables and frequency of serodiscordant unprotected anal intercourse (SDUAI).
At post-test, intentions to avoid transmission were significantly higher in the sexual health arms. However, SDUAI frequency decreased equally across all arms, from 15.0 at baseline to 11.5 at 18 months. HIV+MSM engaging in SDUAI at baseline were more likely to leave the study.
Tailoring interventions to HIV+MSM does not appear to increase the effectiveness of HIV prevention. A sexual health approach appears no more effective than video-based HIV prevention.
PMCID: PMC3423322  PMID: 20101454
HIV+MSM; MSM; HIV prevention; behavioral interventions; unsafe sex; prevention for positives
6.  Spatiotemporal and Spatial Threshold Models for Relating UV Exposures and Skin Cancer in the Central United States 
The exact mechanisms relating exposure to ultraviolet (UV) radiation and elevated risk of skin cancer remain the subject of debate. For example, there is disagreement on whether the main risk factor is duration of the exposure, its intensity, or some combination of both. There is also uncertainty regarding the form of the dose-response curve, with many authors believing only exposures exceeding a given (but unknown) threshold are important. In this paper we explore methods to estimate such thresholds using hierarchical spatial logistic models based on a sample of a cohort of x-ray technologists for whom we have self-reports of time spent in the sun and numbers of blistering sunburns in childhood. A preliminary goal is to explore the temporal pattern of UV exposure and its gradient. Changes here would imply that identical exposure self-reports from different calendar years may correspond to differing cancer risks.
PMCID: PMC2705173  PMID: 20161236
Conditionally autoregressive (CAR) model; Erythemal exposure; Hierarchical model; Non-melanoma skin cancer

Results 1-6 (6)