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1.  Stress and Coping with Racism and Their Role on Sexual Risk for HIV among African American, Asian/Pacific Islander, and Latino Men Who Have Sex With Men 
Archives of sexual behavior  2014;44(2):411-420.
The deleterious effects of racism on a wide range of health outcomes, including HIV risk, is well documented among racial/ethnic minority groups in the United States. However, little is known about how men of color who have sex with men (MSM) cope with stress from racism and whether the coping strategies they employ buffer against the impact of racism on sexual risk for HIV transmission. We examined associations of stress and coping with racism with unprotected anal intercourse (UAI) in a sample of African American (n = 403), Asian/Pacific Islander (n = 393), and Latino (n = 400) MSM recruited in Los Angeles County, CA during 2008–2009. Almost two-thirds (65%) of the sample reported being stressed as a consequence of racism experienced within the gay community. Overall, 51% of the sample reported having UAI in the prior six months. After controlling for race/ethnicity, age, nativity, marital status, sexual orientation, education, HIV serostatus, and lifetime history of incarceration, the multivariate analysis found statistically significant main effects of stress from racism and avoidance coping on UAI; no statistically significant main effects of dismissal, education/confrontation, and social-support seeking were observed. None of the interactions of stress with the four coping measures were statistically significant. Although stress from racism within the gay community increased the likelihood of engaging in UAI among MSM of color, we found little evidence that coping responses to racism buffered stress from racism. Instead, avoidance coping appears to suggest an increase in UAI.
doi:10.1007/s10508-014-0331-1
PMCID: PMC4305487  PMID: 25060122
sexual orientation; men who have sex with men; Stress; Coping; HIV risk
3.  Likelihood-based analysis of longitudinal data from outcome-related sampling designs 
Biometrics  2013;70(1):44-52.
Summary
Investigators commonly gather longitudinal data to assess changes in responses over time and to relate these changes to within-subject changes in predictors. With rare or expensive outcomes such as uncommon diseases and costly radiologic measurements, outcome-dependent, and more generally outcome-related, sampling plans can improve estimation efficiency and reduce cost. Longitudinal follow up of subjects gathered in an initial outcome-related sample can then be used to study the trajectories of responses over time and to assess the association of changes in predictors within subjects with change in response. In this paper we develop two likelihood-based approaches for fitting generalized linear mixed models (GLMMs) to longitudinal data from a wide variety of outcome-related sampling designs. The first is an extension of the semi-parametric maximum likelihood approach developed in and applies quite generally. The second approach is an adaptation of standard conditional likelihood methods and is limited to random intercept models with a canonical link. Data from a study of Attention Deficit Hyperactivity Disorder in children motivates the work and illustrates the findings.
doi:10.1111/biom.12108
PMCID: PMC3954410  PMID: 24571396
Conditional likelihood; Retrospective sampling; Subject-specific models
4.  Social Network Characteristics and HIV Risk among African American, Asian/Pacific Islander, and Latino Men Who Have Sex with Men 
Journal of acquired immune deficiency syndromes (1999)  2013;64(5):10.1097/QAI.0b013e3182a7ee52.
Objectives
To examine how social networks influence HIV risk among U.S. racial/ethnic minority men who have sex with men (MSM) and whether the associations of social network characteristics with risk vary by race/ethnicity.
Methods
A chain-referral sample of 403 African American, 393 Asian/Pacific Islander, and 400 Latino MSM recruited in Los Angeles County, CA completed a questionnaire, which asked about their egocentric social networks, safer sex peer norms, and male anal intercourse partners. HIV-nonconcordant partnerships were those reported by respondents as serodisconcordant or where self and/or partner serostatus was unknown.
Results
Overall, 26% of the sample reported HIV-nonconcordant unprotected anal intercourse (UAI) with a non-primary male partner in the prior six months. In a GEE logistic model that controlled for race/ethnicity, age, nativity, incarceration history, and HIV status, being in a more dense network was associated with less HIV-nonconcordant UAI (adjusted odds ratio [AOR]=0.92, 95% confidence interval [CI]=0.86–0.99, p=0.0467). In addition, the effect of safer sex peer norms on HIV-nonconcordant UAI was moderated by ego-alter closeness (p=0.0021). Safer sex peer norms were protective among those reporting “medium” or “high” ego-alter closeness (AOR=0.70, 95% CI=0.52–0.95, p=0.0213 and AOR=0.48, 95% CI=0.35–0.66, p<0.0001, respectively), but not among those reporting “low” ego-alter closeness (AOR=0.96, 95% CI=0.63–1.46, p=0.8333). The effects of density, closeness, and norms on HIV-nonconcordant UAI did not differ by race/ethnicity.
Conclusions
The significant association of social network characteristics with UAI point to network-level factors as important loci for both ongoing research and HIV prevention interventions among U.S. MSM of color.
doi:10.1097/QAI.0b013e3182a7ee52
PMCID: PMC3830654  PMID: 23933767
Social networks; HIV risk; men who have sex with men; African American; Asian and Pacific Islander; Latino
5.  Experiences of Discrimination and Their Impact on the Mental Health among African American, Asian and Pacific Islander, and Latino Men Who Have Sex with Men 
American journal of public health  2013;103(5):868-874.
Objectives
We examined the associations between specific types and sources of discrimination and mental health outcomes among U.S. racial/ethnic minority men who have sex with men (MSM) and how these associations vary by race/ethnicity.
Methods
A chain-referral sample of 403 African American, 393 Asian and Pacific Islander (API), and 400 Latino MSM recruited in Los Angeles County, CA completed a standardized questionnaire.
Results
Past-year experiences of racism within the general community and perceived homophobia among heterosexual friends were positively associated with depression and anxiety. Past-year homophobia experienced within the general community was also positively associated with anxiety. These statistically significant associations did not vary across racial/ethnic groups. The positive association of perceived racism within the gay community with anxiety differed by race/ethnicity, and was statistically significant only for APIs. Perceived homophobia within the family was not associated with either depression or anxiety.
Conclusions
Higher levels of experiences of discrimination were associated with psychological distress among MSM of color. However, specific types and sources of discrimination were differentially linked to negative mental health outcomes among African American, API, and Latino MSM.
doi:10.2105/AJPH.2012.301052
PMCID: PMC3625493  PMID: 23488483
6.  A note on Type II error under random effects misspecification in generalized linear mixed models 
Biometrics  2011;67(2):654-660.
Summary
Litière et al. (2007) presented the results of simulation studies that they claimed showed that misspecification of the shape of the random effects distribution can produce marked increases in Type II error (decreases in power) of tests based on fits of generalized linear mixed models. However, the paper contains a logical fallacy that invalidates this claim. We present logically correct simulation studies that demonstrate little increase in Type II error, consistent with the earlier work that shows little effect due to misspecification.
doi:10.1111/j.1541-0420.2010.01474.x
PMCID: PMC3079788  PMID: 21689077
Conditional likelihood; generalized linear mixed models; misspecified random effect distributions; power
7.  Progression of Biopsy-Measured Liver Fibrosis in Untreated Patients with Hepatitis C Infection: Non-Markov Multistate Model Analysis 
PLoS ONE  2011;6(5):e20104.
Background
Fibrosis stages from liver biopsies reflect liver damage from hepatitis C infection, but analysis is challenging due to their ordered but non-numeric nature, infrequent measurement, misclassification, and unknown infection times.
Methods
We used a non-Markov multistate model, accounting for misclassification, with multiple imputation of unknown infection times, applied to 1062 participants of whom 159 had multiple biopsies. Odds ratios (OR) quantified the estimated effects of covariates on progression risk at any given time.
Results
Models estimated that progression risk decreased the more time participants had already spent in the current stage, African American race was protective (OR 0.75, 95% confidence interval 0.60 to 0.95, p = 0.018), and older current age increased risk (OR 1.33 per decade, 95% confidence interval 1.15 to 1.54, p = 0.0002). When controlled for current age, older age at infection did not appear to increase risk (OR 0.92 per decade, 95% confidence interval 0.47 to 1.79, p = 0.80). There was a suggestion that co-infection with human immunodeficiency virus increased risk of progression in the era of highly active antiretroviral treatment beginning in 1996 (OR 2.1, 95% confidence interval 0.97 to 4.4, p = 0.059). Other examined risk factors may influence progression risk, but evidence for or against this was weak due to wide confidence intervals. The main results were essentially unchanged using different assumed misclassification rates or imputation of age of infection.
Discussion
The analysis avoided problems inherent in simpler methods, supported the previously suspected protective effect of African American race, and suggested that current age rather than age of infection increases risk. Decreasing risk of progression with longer time already spent in a stage was also previously found for post-transplant progression. This could reflect varying disease activity, with recent progression indicating active disease and high risk, while longer time already spent in a stage indicates quiescent disease and low risk.
doi:10.1371/journal.pone.0020104
PMCID: PMC3103523  PMID: 21637766
8.  Non-Markov Multistate Modeling Using Time-Varying Covariates, with Application to Progression of Liver Fibrosis due to Hepatitis C Following Liver Transplant* 
Multistate modeling methods are well-suited for analysis of some chronic diseases that move through distinct stages. The memoryless or Markov assumptions typically made, however, may be suspect for some diseases, such as hepatitis C, where there is interest in whether prognosis depends on history. This paper describes methods for multistate modeling where transition risk can depend on any property of past progression history, including time spent in the current stage and the time taken to reach the current stage. Analysis of 901 measurements of fibrosis in 401 patients following liver transplantation found decreasing risk of progression as time in the current stage increased, even when controlled for several fixed covariates. Longer time to reach the current stage did not appear associated with lower progression risk. Analysis of simulation scenarios based on the transplant study showed that greater misclassification of fibrosis produced more technical difficulties in fitting the models and poorer estimation of covariate effects than did less misclassification or error-free fibrosis measurement. The higher risk of progression when less time has been spent in the current stage could be due to varying disease activity over time, with recent progression indicating an “active” period and consequent higher risk of further progression.
doi:10.2202/1557-4679.1213
PMCID: PMC2836212  PMID: 20305705
fibrosis; hepatitis C; liver transplant; memoryless assumptions; multistate modeling
9.  Estimating Complex Multi-State Misclassification Rates for Biopsy-Measured Liver Fibrosis in Patients with Hepatitis C* 
For both clinical and research purposes, biopsies are used to classify liver damage known as fibrosis on an ordinal multi-state scale ranging from no damage to cirrhosis. Misclassification can arise from reading error (misreading of a specimen) or sampling error (the specimen does not accurately represent the liver). Studies of biopsy accuracy have not attempted to synthesize these two sources of error or to estimate actual misclassification rates from either source. Using data from two studies of reading error and two of sampling error, we find surprisingly large possible misclassification rates, including a greater than 50% chance of misclassification for one intermediate stage of fibrosis. We find that some readers tend to misclassify consistently low or consistently high, and some specimens tend to be misclassified low while others tend to be misclassified high. Non-invasive measures of liver fibrosis have generally been evaluated by comparison to simultaneous biopsy results, but biopsy appears to be too unreliable to be considered a gold standard. Non-invasive measures may therefore be more useful than such comparisons suggest. Both stochastic uncertainty and uncertainty about our model assumptions appear to be substantial. Improved studies of biopsy accuracy would include large numbers of both readers and specimens, greater effort to reduce or eliminate reading error in studies of sampling error, and careful estimation of misclassification rates rather than less useful quantities such as kappa statistics.
doi:10.2202/1557-4679.1139
PMCID: PMC2810974  PMID: 20104258
fibrosis; hepatitis C; kappa statistic; latent variables; misclassification
10.  Estimating Complex Multi-State Misclassification Rates for Biopsy-Measured Liver Fibrosis in Patients with Hepatitis C 
For both clinical and research purposes, biopsies are used to classify liver damage known as fibrosis on an ordinal multi-state scale ranging from no damage to cirrhosis. Misclassification can arise from reading error (misreading of a specimen) or sampling error (the specimen does not accurately represent the liver). Studies of biopsy accuracy have not attempted to synthesize these two sources of error or to estimate actual misclassification rates from either source. Using data from two studies of reading error and two of sampling error, we find surprisingly large possible misclassification rates, including a greater than 50% chance of misclassification for one intermediate stage of fibrosis. We find that some readers tend to misclassify consistently low or consistently high, and some specimens tend to be misclassified low while others tend to be misclassified high. Non-invasive measures of liver fibrosis have generally been evaluated by comparison to simultaneous biopsy results, but biopsy appears to be too unreliable to be considered a gold standard. Non-invasive measures may therefore be more useful than such comparisons suggest. Both stochastic uncertainty and uncertainty about our model assumptions appear to be substantial. Improved studies of biopsy accuracy would include large numbers of both readers and specimens, greater effort to reduce or eliminate reading error in studies of sampling error, and careful estimation of misclassification rates rather than less useful quantities such as kappa statistics.
doi:10.2202/1557-4679.1139
PMCID: PMC2810974  PMID: 20104258

Results 1-10 (10)