Performance of a Claims-Based Frailty Proxy Using Varying Frailty Ascertainment Lookback Windows.

BACKGROUND: Frailty is an aging-related syndrome of reduced physiological reserve to maintain homeostasis. The Faurot frailty index has been validated as a Medicare claims-based proxy for predicting frailty using billing information from a user-specified ascertainment window. OBJECTIVES: We assessed the validity of the Faurot frailty index as a predictor of the frailty phenotype and 1-year mortality using varying frailty ascertainment windows. RESEARCH DESIGN: We identified older adults (66+ y) in Round 5 (2015) of the National Health and Aging Trends Study with Medicare claims linkage. Gold standard frailty was assessed using the frailty phenotype. We calculated the Faurot frailty index using 3, 6, 8, and 12 months of claims prior to the survey or all-available lookback. Model performance for each window in predicting the frailty phenotype was assessed by quantifying calibration and discrimination. Predictive performance for 1-year mortality was assessed by estimating risk differences across claims-based frailty strata. RESULTS: Among 4253 older adults, the 6 and 8-month windows had the best frailty phenotype calibration (calibration slopes: 0.88 and 0.87). All-available lookback had the best discrimination (C-statistic=0.780), but poor calibration. Mortality associations were strongest using a 3-month window and monotonically decreased with longer windows. Subgroup analyses revealed worse performance in Black and Hispanic individuals than counterparts. CONCLUSIONS: The optimal ascertainment window for the Faurot frailty index may depend on the clinical context, and researchers should consider tradeoffs between discrimination, calibration, and mortality. Sensitivity analyses using different durations can enhance the robustness of inferences. Research is needed to improve prediction across racial and ethnic groups.

Mass Probation: Effects of Sentencing Severity on Mental Health for Black and White Individuals.

BACKGROUND: Incarceration is associated with negative impacts on mental health. Probation, a form of community supervision, has been lauded as an alternative. However, the effect of probation versus incarceration on mental health is unclear. Our objective was to estimate the impact on mental health of reducing sentencing severity at individuals' first adult criminal-legal encounter. METHODS: We used the US National Longitudinal Survey on Youth 1997, a nationally representative dataset of youth followed into their mid-thirties. Restricting to those with an adult encounter (arrest, charge alone or no sentence, probation, incarceration), we used parametric g-computation to estimate the difference in mental health at age 30 (Mental Health Inventory-5) if (1) everyone who received incarceration for their first encounter had received probation and (2) everyone who received probation had received no sentence. RESULTS: Among 1835 individuals with adult encounters, 19% were non-Hispanic Black and 65% were non-Hispanic White. Median age at first encounter was 20. Under hypothetical interventions to reduce sentencing, we did not see better mental health overall (Intervention 1, incarceration to probation: RD = -0.01; CI = -0.02, 0.01; Intervention 2, probation to no sentence: RD = 0.00; CI = -0.01, 0.01) or when stratified by race. CONCLUSION: Among those with criminal-legal encounters, hypothetical interventions to reduce sentencing, including incremental sentencing reductions, were not associated with improved mental health. Future work should consider the effects of preventing individuals' first criminal-legal encounter.

Comparative Effect of Loop Diuretic Prescription on Mortality and Heart Failure Readmission.

Loop diuretics are a standard pharmacologic therapy in heart failure (HF) management. Although furosemide is most frequently used, torsemide and bumetanide are increasingly prescribed in clinical practice, possibly because of superior bioavailability. Few real-world comparative effectiveness studies have examined outcomes across all 3 loop diuretics. The study goal was to compare the effects of loop diuretic prescribing at HF hospitalization discharge on mortality and HF readmission. We identified patients in Medicare claims data initiating furosemide, torsemide, or bumetanide after an index HF hospitalization from 2007 to 2017. We estimated 6-month risks of all-cause mortality and a composite outcome (HF readmission or all-cause mortality) using inverse probability of treatment weighting to adjust for relevant confounders. We identified 62,632 furosemide, 1,720 torsemide, and 2,389 bumetanide initiators. The 6-month adjusted all-cause mortality risk was lowest for torsemide (13.2%), followed by furosemide (14.5%) and bumetanide (15.6%). The 6-month composite outcome risk was 21.4% for torsemide, 24.7% for furosemide, and 24.9% for bumetanide. Compared with furosemide, the 6-month all-cause mortality risk was 1.3% (95% confidence interval [CI]: -3.7, 1.0) lower for torsemide and 1.0% (95% CI: -1.2, 3.2) higher for bumetanide, and the 6-month composite outcome risk was 3.3% (95% CI: -6.3, -0.3) lower for torsemide and 0.2% (95% CI: -2.5, 2.9) higher for bumetanide. In conclusion, the findings suggested that the first prescribed loop diuretic following HF hospitalization is associated with clinically important differences in morbidity in older patients receiving torsemide, bumetanide, or furosemide. These differences were consistent for the effect of all-cause mortality alone, but were not statistically significant.

Understanding the Accumulation of Health-Related Inequities Over the Life Course Using the Mean Cumulative Count.

Understanding how health inequities develop over time is necessary to inform interventions, but methods for doing so are underutilized. We provide an example of the accumulation of stressful life events using the mean cumulative count (MCC), which estimates the expected number of events per person as a function of time, allowing for censoring and competing events. Data came from the National Longitudinal Survey of Youth 1997, a nationally representative data set. To compare the MCC with standard practice, we present the proportions of persons experiencing 1, 2, and ≥3 stressful events and the cumulative probability of experiencing at least 1 event by the end of follow-up. Our sample included 6,522 individuals aged 18-33 years who were followed for a median of 14 years. Using the MCC, by age 20 years the expected number of encounters was 56 events per 100 participants for Black non-Hispanic persons, 47 per 100 for White non-Hispanic persons, and 50 per 100 for Hispanic persons. By age 33 years, inequities grew to 117, 99, and 108 events per 100 persons, respectively. The MCC revealed that inequities in stressful events accumulate over the course of early adulthood, partially driven by repeat events; this information was not evident from conventional approaches. This method can be used to identify intervention points for disrupting the accumulation of repeat events to improve health equity.

Health Insurance and Initiation of Direct-Acting Antivirals for Hepatitis C in US Women With Human Immunodeficiency Virus.

BACKGROUND: Direct-acting antiviral (DAA) therapy for hepatitis C virus (HCV) is well tolerated, cost-effective, and yields high sustained virologic response rates, yet it has remained financially inaccessible to many patients. METHODS: Participants of the Women's Interagency HIV Study (an observational US cohort) with human immunodeficiency virus (HIV) and HCV (RNA+) reporting no prior hepatitis C treatment were followed for DAA initiation (2015-2019). We estimated risk ratios (RRs) of the relationship between time-varying health insurance status and DAA initiation, adjusting for confounders with stabilized inverse probability weights. We also estimated weighted cumulative incidences of DAA initiation by health insurance status. RESULTS: A total of 139 women (74% Black) were included; at baseline, the median age was 55 years and 86% were insured. Most had annual household incomes ≤$18 000 (85%); advanced liver fibrosis (21%), alcohol use (45%), and recreational drug use (35%) were common. Across 439 subsequent semiannual visits, 88 women (63%) reported DAA initiation. Compared with no health insurance, health insurance increased the likelihood of reporting DAA initiation at a given visit (RR, 4.94; 95% confidence limit [CL], 1.92 to 12.8). At 2 years, the weighted cumulative incidence of DAA initiation was higher among the insured (51.2%; 95% CL, 43.3% to 60.6%) than the uninsured (3.5%; 95% CL, 0.8% to 14.6%). CONCLUSIONS: Accounting for clinical, behavioral, and sociodemographic factors over time, health insurance had a substantial positive effect on DAA initiation. Interventions to increase insurance coverage should be prioritized to increase HCV curative therapy uptake for persons with HIV.

Trimodality Therapy vs Definitive Chemoradiation in Older Adults With Locally Advanced Esophageal Cancer.

BACKGROUND: The comparative effectiveness of trimodality therapy vs definitive chemoradiation for treating locally advanced esophageal cancer in older adults is uncertain. Existing trials lack generalizability to older adults, a population with heightened frailty. We sought to emulate a hypothetical trial comparing these treatments using real-world data. METHODS: A cohort of adults aged 66-79 years diagnosed with locally advanced esophageal cancer between 2004 and 2017 was identified in the Surveillance Epidemiology and End Results-Medicare database. The clone-censor-weight method was leveraged to eliminate time-related biases when comparing outcomes between treatments. Outcomes included overall mortality, esophageal cancer-specific mortality, functional adverse events, and healthy days at home. RESULTS: A total of 1240 individuals with adenocarcinomas and 661 with squamous cell carcinomas were identified. For adenocarcinomas, the standardized 5-year risk of mortality was 73.4% for trimodality therapy and 83.8% for definitive chemoradiation (relative risk [RR] = 0.88, 95% confidence interval [CI] = 0.82 to 0.95). Trimodality therapy was associated with mortality risk reduction for squamous cell carcinomas (RR = 0.87, 95% CI = 0.70 to 1.01). The 1-year incidence of functional adverse events was higher in the trimodality group (adenocarcinomas RR = 1.40, 95% CI = 1.22 to 1.65; squamous cell carcinomas RR = 1.21, 95% CI = 1.00 to 1.49). Over 5 years, trimodality therapy was associated with 160 (95% CI = 67 to 229) and 177 (95% CI = 51 to 313) additional home days in individuals with adenocarcinomas and squamous cell carcinomas, respectively. CONCLUSIONS: Compared with definitive chemoradiation, trimodality therapy was associated with reduced mortality but increased risk of function-related adverse events. Discussing these tradeoffs may help optimize care plans.

Patterns of care amongst older adults diagnosed with locally advanced esophageal cancer: A cohort study.

INTRODUCTION: Since the early 2010s, neoadjuvant chemoradiation followed by esophagectomy (trimodal therapy) has been a recommended treatment for patients diagnosed with locally advanced esophageal cancer. However, it may also add treatment-related toxicity, particularly for older adults with significant comorbidity and frailty burdens. We examined contemporary patterns of care in older adults, which have not been well characterized. MATERIALS AND METHODS: We used the Surveillance Epidemiology and End Results-Medicare database to identify a cohort of US adults aged 66 years and older diagnosed with incident locally advanced esophageal cancer between 2004 and 2017. Calendar year age-standardized percentages of treatment receipt were calculated. Joinpoint regression was used to detect temporal trends in treatment receipt. Descriptive associations between patient factors and treatment were assessed. Trend analyses quantified how the percentage of trimodal and definitive chemoradiation (no surgery) patients receiving cisplatin-based, carboplatin-based, and other chemotherapy regimens evolved over time. RESULTS: In total, 4332 adults aged ≥66 years with locally advanced esophageal cancer were included. The age-standardized percentage of patients receiving trimodal therapy increased from 16.7% in 2004 to 26.1% in 2017 (annual percent change = 3.5%; 95% confidence interval [CI], 0.7%-6.4%) in adenocarcinomas and from 7.3% in 2004 to 9.1% in 2017 (annual percent change = 0.4%; 95% CI, -4.1%-5.1%) in squamous cell carcinomas. By 2017, definitive chemoradiation became the most frequently used treatment modality for adenocarcinomas (49.8%; 95% CI, 43.5-56.0) and squamous cell carcinomas (59.5%; 95% CI, 50.8-68.2). Patients with higher comorbidity and frailty burdens were less likely to be treated with trimodal therapy. Amongst patients receiving chemoradiation as part of their treatment, a large and swift channeling away from cisplatin and towards carboplatin-based regimens was observed. DISCUSSION: In practice, definitive chemoradiation is the most commonly received treatment by older adults with locally advanced esophageal cancer. Four out of five older adults do not receive trimodal therapy, some of whom are potentially undertreated.

A Two-stage Approach for Rapid Assessment of the Proportion Achieving Viral Suppression Using Routine Clinical Data.

BACKGROUND: Improving viral suppression among people with HIV reduces morbidity, mortality, and transmission. Accordingly, monitoring the proportion of patients with a suppressed viral load is important to optimizing HIV care and treatment programs. But viral load data are often incomplete in clinical records. We illustrate a two-stage approach to estimate the proportion of treated people with HIV who have a suppressed viral load in the Dominican Republic. METHODS: Routinely collected data on viral load and patient characteristics were recorded in a national database, but 74% of patients on treatment at the time of the study did not have a recent viral load measurement. We recruited a subset of these patients for a rapid assessment that obtained additional viral load measurements. We combined results from the rapid assessment and main database using a two-stage weighting approach and compared results to estimates obtained using standard approaches to account for missing data. RESULTS: Of patients with recent routinely collected viral load data, 60% had a suppressed viral load. Results were similar after applying standard approaches to account for missing data. Using the two-stage approach, we estimated that 77% (95% confidence interval [CI] = 74, 80) of those on treatment had a suppressed viral load. CONCLUSIONS: When assessing the proportion of people on treatment with a suppressed viral load using routinely collected data, applying standard approaches to handle missing data may be inadequate. In these settings, augmenting routinely collected data with data collected through sampling-based approaches could allow more accurate and efficient monitoring of HIV treatment program effectiveness.

A new smoking cessation 'cascade' among women with or at risk for HIV infection.

OBJECTIVES: The aim of this study was to define a smoking cessation 'cascade' among USA women with and without HIV and examine differences by sociodemographic characteristics. DESIGN: An observational cohort study using data from smokers participating in the Women's Interagency HIV Study between 2014 and 2019. METHODS: We followed 1165 women smokers with and without HIV from their first study visit in 2014 or 2015 until an attempt to quit smoking within approximately 3 years of follow-up, initial cessation (i.e. no restarting smoking within approximately 6 months of a quit attempt), and sustained cessation (i.e. no restarting smoking within approximately 12 months of a quit attempt). Using the Aalen-Johansen estimator, we estimated the cumulative probability of achieving each step, accounting for the competing risk of death. RESULTS: Forty-five percent of smokers attempted to quit, 27% achieved initial cessation, and 14% achieved sustained cessation with no differences by HIV status. Women with some post-high school education were more likely to achieve each step than those with less education. Outcomes did not differ by race. Thirty-six percent [95% confidence interval (95% CI): 31-42] of uninsured women attempted to quit compared with 47% (95% CI: 44-50) with Medicaid and 49% (95% CI: 41-59) with private insurance. CONCLUSION: To decrease smoking among USA women with and without HIV, targeted, multistage interventions, and increased insurance coverage are needed to address shortfalls along this cascade.

A Geography of Risk: Structural Racism and Coronavirus Disease 2019 Mortality in the United States.

Coronavirus disease 2019 (COVID-19) is disproportionately burdening racial and ethnic minority groups in the United States. Higher risks of infection and mortality among racialized minorities are a consequence of structural racism, reflected in specific policies that date back centuries and persist today. Yet our surveillance activities do not reflect what we know about how racism structures risk. When measuring racial and ethnic disparities in deaths due to COVID-19, the Centers for Disease Control and Prevention statistically accounts for the geographic distribution of deaths throughout the United States to reflect the fact that deaths are concentrated in areas with different racial and ethnic distributions from those of the larger United States. In this commentary, we argue that such an approach misses an important driver of disparities in COVID-19 mortality, namely the historical forces that determine where individuals live, work, and play, and that consequently determine their risk of dying from COVID-19. We explain why controlling for geography downplays the disproportionate burden of COVID-19 on racialized minority groups in the United States. Finally, we offer recommendations for the analysis of surveillance data to estimate racial disparities, including shifting from distribution-based to risk-based measures, to help inform a more effective and equitable public health response to the pandemic.

Comparative Effectiveness and Harms of Antibiotics for Outpatient Diverticulitis : Two Nationwide Cohort Studies.

BACKGROUND: Outpatient diverticulitis is commonly treated with either a combination of metronidazole and a fluoroquinolone (metronidazole-with-fluoroquinolone) or amoxicillin-clavulanate alone. The U.S. Food and Drug Administration advised that fluoroquinolones be reserved for conditions with no alternative treatment options. The comparative effectiveness of metronidazole-with-fluoroquinolone versus amoxicillin-clavulanate for diverticulitis is uncertain. OBJECTIVE: To determine the effectiveness and harms of metronidazole-with-fluoroquinolone versus amoxicillin-clavulanate for outpatient diverticulitis. DESIGN: Active-comparator, new-user, retrospective cohort studies. SETTING: Nationwide population-based claims data on U.S. residents aged 18 to 64 years with private employer-sponsored insurance (2000 to 2018) or those aged 65 years or older with Medicare (2006 to 2015). PARTICIPANTS: Immunocompetent adults with diverticulitis in the outpatient setting. INTERVENTION: Metronidazole-with-fluoroquinolone or amoxicillin-clavulanate. MEASUREMENTS: 1-year risks for inpatient admission, urgent surgery, and Clostridioides difficile infection (CDI) and 3-year risk for elective surgery. RESULTS: In MarketScan (IBM Watson Health), new users of metronidazole-with-fluoroquinolone (n = 106 361) and amoxicillin-clavulanate (n = 13 160) were identified. There were no differences in 1-year admission risk (risk difference, 0.1 percentage points [95% CI, -0.3 to 0.6]), 1-year urgent surgery risk (risk difference, 0.0 percentage points [CI, -0.1 to 0.1]), 3-year elective surgery risk (risk difference, 0.2 percentage points [CI, -0.3 to 0.7]), or 1-year CDI risk (risk difference, 0.0 percentage points [CI, -0.1 to 0.1]) between groups. In Medicare, new users of metronidazole-with-fluoroquinolone (n = 17 639) and amoxicillin-clavulanate (n = 2709) were identified. There were no differences in 1-year admission risk (risk difference, 0.1 percentage points [CI, -0.7 to 0.9]), 1-year urgent surgery risk (risk difference, -0.2 percentage points [CI, -0.6 to 0.1]), or 3-year elective surgery risk (risk difference, -0.3 percentage points [CI, -1.1 to 0.4]) between groups. The 1-year CDI risk was higher for metronidazole-with-fluoroquinolone than for amoxicillin-clavulanate (risk difference, 0.6 percentage points [CI, 0.2 to 1.0]). LIMITATION: Residual confounding is possible, and not all harms associated with these antibiotics, most notably drug-induced liver injury, could be assessed. CONCLUSION: Treating diverticulitis in the outpatient setting with amoxicillin-clavulanate may reduce the risk for fluoroquinolone-related harms without adversely affecting diverticulitis-specific outcomes. PRIMARY FUNDING SOURCE: National Institutes of Health.

The Burden of Malaria in the Democratic Republic of the Congo.

Despite evidence that older children and adolescents bear the highest burden of malaria, large malaria surveys focus on younger children. We used polymerase chain reaction data from the 2013-2014 Demographic and Health Survey in the Democratic Republic of Congo (including children aged <5 years and adults aged ≥15 years) and a longitudinal study in Kinshasa Province (participants aged 6 months to 98 years) to estimate malaria prevalence across age strata. We fit linear models and estimated prevalences for each age category; adolescents aged 10-14 years had the highest prevalence. We estimate approximately 26 million polymerase chain reaction-detectable infections nationally. Adolescents and older children should be included in surveillance studies.

Reweighting Oranges to Apples: Transported RE-LY Trial Versus Nonexperimental Effect Estimates of Anticoagulation in Atrial Fibrillation.

BACKGROUND: Results from trials and nonexperimental studies are often directly compared, with little attention paid to differences between study populations. When target and trial population data are available, accounting for these differences through transporting trial results to target populations of interest provides useful perspective. We aimed to compare two-year risk differences (RDs) for ischemic stroke, mortality, and gastrointestinal bleeding in older adults with atrial fibrillation initiating dabigatran and warfarin when using trial transport methods versus nonexperimental methods. METHODS: We identified Medicare beneficiaries who initiated warfarin or dabigatran from a 20% nationwide sample. To transport treatment effects observed in the randomized evaluation of long-term anticoagulation trial, we applied inverse odds weights to standardize estimates to two Medicare target populations of interest, initiators of: (1) dabigatran and (2) warfarin. Separately, we conducted a nonexperimental study in the Medicare populations using standardized morbidity ratio weighting to control measured confounding. RESULTS: Comparing dabigatran to warfarin, estimated two-year RDs for ischemic stroke were similar with trial transport and nonexperimental methods. However, two-year mortality RDs were closer to the null when using trial transport versus nonexperimental methods for the dabigatran target population (transported RD: -0.57%; nonexperimental RD: -1.9%). Estimated gastrointestinal bleeding RDs from trial transport (dabigatran initiator RD: 1.8%; warfarin initiator RD: 1.9%) appeared more harmful than nonexperimental results (dabigatran initiator RD: 0.14%; warfarin initiator RD: 0.57%). CONCLUSIONS: Differences in study populations can and should be considered quantitatively to ensure results are relevant to populations of interest, particularly when comparing trial with nonexperimental findings. See video abstract: http://links.lww.com/EDE/B703.

Two-stage g-computation: Evaluating Treatment and Intervention Impacts in Observational Cohorts When Exposure Information Is Partly Missing.

Illustrations of the g-computation algorithm to evaluate population average treatment and intervention effects have been predominantly implemented in settings with complete exposure information. Thus, worked examples of approaches to handle missing data in this causal framework are needed to facilitate wider use of these estimators. We illustrate two-stage g-computation estimators that leverage partially observed information on the full study sample and complete exposure information on a subset to estimate causal effects. In a hypothetical cohort of 1,623 human immunodeficiency virus (HIV)-positive women with 30% complete opioid prescription information, we illustrate a two-stage extrapolation g-computation estimator for the average treatment effect of shorter or longer duration opioid prescriptions; we further illustrate two-stage inverse probability weighting and imputation g-computation estimators for the average intervention effect of shortening the duration of prescriptions relative to the status quo. Two-stage g-computation estimators approximated the true risk differences for the population average treatment and intervention effects while g-computation fit to the subset of complete cases was biased. In 10,000 Monte Carlo simulations, two-stage approaches considerably reduced bias and mean squared error and improved the coverage of 95% confidence limits. Although missing data threaten validity and precision, two-stage g-computation designs offer principled approaches to handling missing information.

Real-world on-treatment and initial treatment absolute risk differences for dabigatran vs warfarin in older US adults.

PURPOSE: Trials and past observational work compared dabigatran and warfarin in patients with atrial fibrillation, but few reported estimates of absolute harm and benefit under real-world adherence patterns, particularly in older adults that may have differing benefit-harm profiles. We aimed to estimate risk differences for ischemic stroke, death, and gastrointestinal bleeding after initiating dabigatran and warfarin in older adults (a) when patients adhere to treatment and (b) under real-world adherence patterns. METHODS: In a 20% sample of nationwide Medicare claims from 2010 to 2015, we identified beneficiaries aged 66 years and older initiating warfarin and dabigatran. We followed individuals from initiation until death or October 2015 (initial treatment, IT) and separately censored individuals' follow-up after drug switches and gaps in supply (on-treatment, OT). We applied inverse probability of treatment and standardized morbidity ratio weights, as well as inverse probability of censoring weights, to estimate two-year risk differences (RDs) for dabigatran vs warfarin. RESULTS: We identified 10,717 dabigatran and 74,891 warfarin initiators. Weighted OT RDs suggested decreased ischemic stroke risk for dabigatran vs warfarin; IT RDs indicated increased or no change in ischemic stroke risk. Regardless of follow-up approach and weighting strategy, risk of death appeared lower and risk of gastrointestinal bleeding appeared higher when comparing dabigatran vs warfarin. CONCLUSIONS: Dabigatran use was associated with lower risks of mortality and ischemic stroke in routine care when older adults stayed on treatment. IT analyses suggested that these benefits may be diminished under real-world patterns of switching and discontinuation.

Nonparametric estimation of the cumulative incidence function under outcome misclassification using external validation data.

Misclassification of outcomes or event types is common in health sciences research and can lead to serious bias when estimating the cumulative incidence functions in settings with competing risks. Recent work has shown how to estimate nonparametric cumulative incidence functions in the presence of nondifferential outcome misclassification when the misclassification probabilities are known. Here, we extend this approach to account for misclassification that is differential with respect to important predictors of the outcome using misclassification probabilities estimated from external validation data. Moreover, we propose a bootstrap approach in which the observations from both the main study data and the external validation study are resampled to allow the uncertainty in the misclassification probabilities to propagate through the analysis into the final confidence intervals, ensuring appropriate confidence interval coverage probabilities. The proposed estimator is shown to be uniformly consistent and simulation studies indicate that both the estimator and the standard error estimation approach perform well in finite samples. The methodology is applied to estimate the cumulative incidence of death and disengagement from HIV care in a large cohort of HIV infected individuals in sub-Saharan Africa, where a significant death underreporting issue leads to outcome misclassification. This analysis uses external validation data from a separate study conducted in the same country.

Estimating Hidden Population Sizes with Venue-based Sampling: Extensions of the Generalized Network Scale-up Estimator.

BACKGROUND: Researchers use a variety of population size estimation methods to determine the sizes of key populations at elevated risk of human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), an important step in quantifying epidemic impact, advocating for high-risk groups, and planning, implementing, and monitoring prevention, care, and treatment programs. Conventional procedures often use information about sample respondents' social network contacts to estimate the sizes of key populations of interest. A recent study proposes a generalized network scale-up method that combines two samples-a traditional sample of the general population and a link-tracing sample of the hidden population-and produces more accurate results with fewer assumptions than conventional approaches. METHODS: We extended the generalized network scale-up method from link-tracing samples to samples collected with venue-based sampling designs popular in sampling key populations at risk of HIV. Our method obviates the need for a traditional sample of the general population, as long as the size of the venue-attending population is approximately known. We tested the venue-based generalized network scale-up method in a comprehensive simulation evaluation framework. RESULTS: The venue-based generalized network scale-up method provided accurate and efficient estimates of key population sizes, even when few members of the key population were sampled, yielding average biases below ±6% except when false-positive reporting error is high. It relies on limited assumptions and, in our tests, was robust to numerous threats to inference. CONCLUSIONS: Key population size estimation is vital to the successful implementation of efforts to combat HIV/AIDS. Venue-based network scale-up approaches offer another tool that researchers and policymakers can apply to these problems.

Achieving the first 90 for key populations in sub-Saharan Africa through venue-based outreach: challenges and opportunities for HIV prevention based on PLACE study findings from Malawi and Angola.

INTRODUCTION: Providing outreach HIV prevention services at venues (i.e. "hotspots") where people meet new sex partners can decrease barriers to HIV testing services (HTS) for key populations (KP) in sub-Saharan Africa (SSA). We offered venue-based HTS as part of bio-behavioural surveys conducted in urban Malawi and Angola to generate regional insights into KP programming gaps and identify opportunities to achieve the "first 90" for KP in SSA. METHODS: From October 2016 to March 2017, we identified and verified 1054 venues in Luanda and Benguela, Angola and Zomba, Malawi and conducted bio-behavioural surveys at 166 using the PLACE method. PLACE interviews community informants to systematically identify public venues where KP can be reached and conducts bio-behavioural surveys at a stratified random sample of venues. We present survey results using summary statistics and multivariable modified Poisson regression modelling to examine associations between receipt of outreach worker-delivered HIV/AIDS education and HTS uptake. We applied sampling weights to estimate numbers of HIV-positive KP unaware of their status at venues. RESULTS: We surveyed 959 female sex workers (FSW), 836 men who have sex with men (MSM), and 129 transgender women (TGW). An estimated 71% of HIV-positive KP surveyed were not previously aware of their HIV status, receiving a new HIV diagnosis through PLACE venue-based HTS. If venue-based HTS were implemented at all venues, 2022 HIV-positive KP (95% CI: 1649 to 2477) who do not know their status could be reached, including 1666 FSW (95% CI: 1397 to 1987), 274 MSM (95% CI: 160 to 374), and 82 TG (95% CI: 20 to 197). In multivariable analyses, FSW, MSM, and TGW who received outreach worker-delivered HIV/AIDS education were 3.15 (95% CI: 1.99 to 5.01), 3.12 (95% CI: 2.17 to 4.48), and 1.80 (95% CI: 0.67 to 4.87) times as likely, respectively, as those who did not to have undergone HTS within the last six months. Among verified venues, <=68% offered any on-site HIV prevention services. CONCLUSIONS: Availability of HTS and other HIV prevention services was limited at venues. HIV prevention can be delivered at venues, which can increase HTS uptake and HIV diagnosis among individuals not previously aware of their status. Delivering venue-based HTS may represent an effective strategy to reach the "first 90" for KP in SSA.

Conditional cash transfers and the reduction in partner violence for young women: an investigation of causal pathways using evidence from a randomized experiment in South Africa (HPTN 068).

INTRODUCTION: Evidence has shown that the experience of violence by a partner has important influences on women's risk of HIV acquisition. Using a randomized experiment in northeast South Africa, we found that a conditional cash transfer (CCT) targeted to poor girls in high school reduced the risk of physical intimate partner violence (IPV) in the past 12 months by 34%. The purpose of this analysis is to understand the pathways through which the CCT affects IPV. METHODS: HPTN 068 was a phase 3, randomized controlled trial in rural Mpumalanga province, South Africa. Eligible young women (aged 13-20) and their parents or guardians were randomly assigned (1:1) to either receive a monthly cash transfer conditional on monthly high school attendance or no cash transfer. Between 2011 and 2015, participants (N = 2,448) were interviewed at baseline, then at annual follow-up visits at 12, 24 and 36 months. The total effect of the CCT on IPV was estimated using a GEE log-binomial regression model. We then estimated controlled direct effects to examine mediation of direct effects through intermediate pathways. Mediators include sexual partnership measures, the sexual relationship power scale, and household consumption measures. RESULTS: We found evidence that the CCT works in part through delaying sexual debut or reducing the number of sexual partners. The intervention interacts with these mediators leading to larger reductions in IPV risk compared to the total effect of the CCT on any physical IPV [RR 0.66, CI(95%):0.59-0.74]. The largest reductions are seen when we estimate the controlled direct effect under no sexual debut [RR 0.57, CI(95%):0.48-0.65] or under no sexual partner in the last 12 months [RR 0.53, CI(95%):0.46-0.60]. CONCLUSIONS: Results indicate that a CCT for high school girls has protective effects on their experience of IPV and that the effect is due in part to girls choosing not to engage in sexual partnerships, thereby reducing the opportunity for IPV. As a lower exposure to IPV and safer sexual behaviours also protect against HIV acquisition, this study adds to the growing body of evidence on how cash transfers may reduce young women's HIV risk.

Multiple Imputation to Account for Measurement Error in Marginal Structural Models.

BACKGROUND: Marginal structural models are an important tool for observational studies. These models typically assume that variables are measured without error. We describe a method to account for differential and nondifferential measurement error in a marginal structural model. METHODS: We illustrate the method estimating the joint effects of antiretroviral therapy initiation and current smoking on all-cause mortality in a United States cohort of 12,290 patients with HIV followed for up to 5 years between 1998 and 2011. Smoking status was likely measured with error, but a subset of 3,686 patients who reported smoking status on separate questionnaires composed an internal validation subgroup. We compared a standard joint marginal structural model fit using inverse probability weights to a model that also accounted for misclassification of smoking status using multiple imputation. RESULTS: In the standard analysis, current smoking was not associated with increased risk of mortality. After accounting for misclassification, current smoking without therapy was associated with increased mortality (hazard ratio [HR]: 1.2 [95% confidence interval [CI] = 0.6, 2.3]). The HR for current smoking and therapy [0.4 (95% CI = 0.2, 0.7)] was similar to the HR for no smoking and therapy (0.4; 95% CI = 0.2, 0.6). CONCLUSIONS: Multiple imputation can be used to account for measurement error in concert with methods for causal inference to strengthen results from observational studies.