Statistical Methods for Clinical Trials with Multiple Outcomes, HIV Surveillance, and Nonparametric Meta-Analysis

Central to the goals of public health are obtaining and interpreting timely and relevant information for the benefit of humanity. In this dissertation, we propose methods to monitor and assess the spread HIV in a more rapid manner, as well as to improve decisions regarding patient treatment options. In Chapter 1, we propose a method, extending the previously proposed dual-testing algorithm and augmented cross-sectional design, for estimating the HIV incidence rate in a particular community. Compared to existing methods, our proposed estimator allows for shorter follow-up time and does not require estimation of the mean window period, a crucial, but often unknown, parameter. The estimator performs well in a wide range of simulation settings. We discuss when this estimator would be expected to perform well and offer design considerations for the implementation of such a study. Chapters 2 and 3 are concerned with obtaining a more complete understanding of the impact of treatment in randomized clinical trials in which multiple patient outcomes are recorded. Chapter 2 provides an illustration of methods that may be used to address concerns of both risk-benefit analysis and personalized medicine simultaneously, with a goal of successfully identifying patients who will be ideal candidates for future treatment. Riskbenefit analysis is intended to address the multivariate nature of patient outcomes, while “personalized medicine” is concerned with patient heterogeneity, both of which complicate the determination of a treatment’s usefulness. A third complicating factor is the duration of treatment use. Chapter 3 features proposed methods for assessing the impact of treatment as a function of time, as well as methods for summarizing the impact of treatment across a range of follow-up times. Chapter 4 addresses the issue of meta-analysis, a commonly used tool for combining information for multiple independent studies, primarily for the purpose of answering a clinical question not suitably addressed by any one single study. This approach has proven highly useful and attractive in recent years, but often relies on parametric assumptions that cannot be verified. We propose a non-parametric approach to meta-analysis, valid in a wider range of scenarios, minimizing concerns over compromised validity

The Myth Of Making Inferences For An Overall Treatment Efficacy With Data From Multiple Comparative Studies Via Meta-analysis

Meta analysis techniques, if applied appropriately, can provide a summary of the totality of evidence regarding an overall difference between a new treatment and a control group using data from multiple comparative clinical studies. The standard meta analysis procedures, however, may not give a meaningful between-group difference summary measure or identify a meaningful patient population of interest, especially when the fixed effect model assumption is not met. Moreover, a single between-group comparison measure without a reference value obtained from patients in the control arm would likely not be informative enough for clinical decision making. In this paper, we propose a simple, robust procedure based on a mixture population concept and provide a clinically meaningful group contrast summary for a well-defined target population. We use the data from a recent meta analysis for evaluating statin therapies with respect to the incidence of fatal stroke events to illustrate the issues associated with the standard meta analysis procedures as well as the advantages of our simple proposal

Increased Epithelial Gaps in the Small Intestine Are Predictive of Hospitalization and Surgery in Patients With Inflammatory Bowel Disease

Objectives: Epithelial gaps resulting from intestinal cell extrusions can be visualized with confocal laser endomicroscopy (CLE) during colonoscopy and increased in normal-appearing terminal ileum of inflammatory bowel disease (IBD) patients. Cell-shedding events on CLE were found to be predictive of disease relapse. The aim of this study was to assess the prognostic value of epithelial gap densities for major clinical events (hospitalization or surgery) in follow-up. Methods: We prospectively followed IBD patients undergoing colonoscopy with probe-based CLE (pCLE) for clinical events including symptom flares, medication changes, hospitalization, or surgery. Survival analysis methods were used to compare event times for the composite outcome of hospitalization or surgery using log-rank tests and Cox proportional hazards models. We also examined the relationship of gap density with IBD flares, need for anti-tumor necrosis factor therapy, disease duration, gender and endoscopic disease severity, and location. Results: A total of 21 Crohn's disease and 20 ulcerative colitis patients with a median follow-up of 14 (11–31) months were studied. Patients with elevated gap density were at significantly higher risk for hospitalization or surgery (log-rank test P=0.02). Gap density was a significant predictor for risk of major events, with a hazard ratio of 1.10 (95% confidence interval=1.01, 1.20) associated with each increase of 1% in gap density. Gap density was also correlated with IBD disease duration (Spearman's correlation coefficient rho=0.44, P=0.004), and was higher in male patients (9.0 vs. 3.6 gaps per 100 cells, P=0.038). Conclusions: Increased epithelial gaps in the small intestine as determined by pCLE are a predictor for future hospitalization or surgery in IBD patients

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

Quantifying treatment effects in trials with multiple event-time outcomes

Background: Data on the occurrence times of multiple outcomes, reflecting the temporal profile of disease burden/progression, have been used to estimate treatment effects in various recent randomized trials. Most procedures for analyzing these data require specific model assumptions. When the assumptions are not met, the results may be misleading. Robust, model-free procedures for study design and analysis that enable clinically meaningful interpretations are warranted. Methods: For each treatment group, we constructed and summarized the estimated mean cumulative count of events over time by the area under the curve (AUC), which can be interpreted as the mean total event-free time lost from multiple undesirable outcomes. A higher curve, and resulting larger AUC, implies a worse treatment. The treatment effect is quantified by the ratio and/or difference of AUCs. The timing and occurrence of recurrent heart failure hospitalizations (HFHs) and cardiovascular (CV) death from Prospective Comparison of ARNI with ARB Global Outcomes in HF with Preserved Ejection Fraction (PARAGON-HF), comparing sacubitril/valsartan with valsartan, are presented for illustration. We also discuss the design of future studies on the basis of the proposed method. Results: With 48 months of follow-up, estimated AUCs, representing the total event-free time lost to HFHs and CV death, were 11.3 and 13.1 event-months for sacubitril/valsartan and valsartan, respectively. The ratio of these AUCs was 0.86 (95% confidence interval, 0.75 to 1.00; P=0.049), a 14% reduction of disease burden favoring combination therapy. A future study, similar to PARAGON-HF, designed using the new proposal would require fewer patients would than a conventional time-to-first-event analysis. Conclusions: The proposed method is robust and model-free and provides a clinically interpretable, time-scale summary of the treatment effect. (Funded by National Institutes of Health.

Application of Diagnostic Algorithms for Heart Failure With Preserved Ejection Fraction to the Community

Objectives This study sought to describe characteristics and risk of adverse outcomes associated with the H2FPEF and HFA-PEFF scores among participants in the community with unexplained dyspnea. Background Diagnosing heart failure with preserved ejection fraction (HFpEF) can be challenging. The H2FPEF and HFA-PEFF scores have recently been developed to estimate the likelihood that HFpEF is present among patients with unexplained dyspnea. Methods The study included 4,892 ARIC (Atherosclerosis Risk In Communities) study participants 67 to 90 years of age at visit 5 (2011 to 2013) without other common cardiopulmonary causes of dyspnea. Participants were categorized as asymptomatic (76.6%), having known HFpEF (10.3%), and having tertiles of each score among those with ≥moderate, self-reported dyspnea (13.1%). The primary outcome was heart failure (HF) hospitalization or death. Results Mean age was 75 ± 5 years, 58% were women, and 22% were black. After a mean follow-up of 5.3 ± 1.2 years, rates of HF hospitalization or death per 1,000 person-years for asymptomatic and known HFpEF were 20.7 (95% confidence interval [CI]: 18.9 to 22.7) and 71.6 (95% CI: 61.6 to 83.3), respectively. Among 641 participants with unexplained dyspnea, rates were 27.7 (95% CI: 18.2 to 42.1), 44.9 (95% CI: 34.9 to 57.7), and 47.3 (95% CI: 36.5 to 61.3) (tertiles of H2FPEF score) and 31.8 (95% CI: 20.3 to 49.9), 32.4 (95% CI: 23.4 to 44.9), and 54.3 (95% CI: 43.8 to 67.3) (tertiles of HFA-PEFF score). Participants with unexplained dyspnea and scores above the diagnostic threshold suggested for each algorithm, H2FPEF score ≥6 and HFA-PEFF score ≥5, had equivalent risk of HF hospitalization or death compared with known HFpEF. Among those with unexplained dyspnea, 28% had “discordant” findings (only high risk by 1 algorithm), while 4% were high risk by both. Conclusions Participants with unexplained dyspnea and higher H2FPEF or HFA-PEFF scores face substantial risks of HF hospitalization or death. A significant fraction of patients are classified discordantly by using both algorithms

Health‐related quality of life in acute heart failure: association between patient‐reported symptoms and markers of congestion

Aims: The aim of this study was to examine the association between patient-reported symptoms and the extent of pulmonary congestion in acute heart failure (AHF). Methods and results: In this prospective, observational study, patient-reported symptoms were assessed at baseline using the Kansas City Cardiomyopathy Questionnaire Total Symptom Score (KCCQ-TSS) (range 0-100; 0 worst) in patients hospitalized for AHF. In a subset, patient-reported dyspnea at rest and on exertion was examined (range 0-10; 10 worst) at baseline. In addition, 4-zone lung ultrasound (LUS) was performed at baseline at the time of echocardiography. B-lines were quantified offline, blinded to clinical findings, in a core laboratory. Chest x-ray (CXR) and physical examination findings were collected from the medical records. Among 322 patients (mean age 72, 60% men, mean LVEF 39%) with AHF, the median KCCQ-TSS score was 33 [interquartile range 18-48]. Worse KCCQ-TSS was associated with worse NYHA class, dyspnea at rest and on exertion, and peripheral edema (p trend <0.001 for all). However, KCCQ-TSS was not associated with the extent of pulmonary congestion, as assessed by the number of B-lines on LUS, or findings on CXR or physical examination (p trend > 0.30 for all). Similarly, KCCQ-TSS was not significantly associated with echocardiographic markers of left ventricular filling pressure, pulmonary pressure or with NT-proBNP. Conclusions: Among patients hospitalized for AHF, at baseline, KCCQ-TSS was not associated with pulmonary congestion assessed by LUS, CXR or physical examination. These findings suggest that the profound reduction in KCCQ-TSS in patients with AHF may not be solely explained by pulmonary congestion

Manipulations in the Peripheral Stalk of the Saccharomyces cerevisiae F1F0-ATP Synthase*

The Saccharomyces cerevisiae F1F0-ATP synthase peripheral stalk is composed of the OSCP, h, d, and b subunits. The b subunit has two membrane-spanning domains and a large hydrophilic domain that extends along one side of the enzyme to the top of F1. In contrast, the Escherichia coli peripheral stalk has two identical b subunits, and subunits with substantially altered lengths can be incorporated into a functional F1F0-ATP synthase. The differences in subunit structure between the eukaryotic and prokaryotic peripheral stalks raised a question about whether the two stalks have similar physical and functional properties. In the present work, the length of the S. cerevisiae b subunit has been manipulated to determine whether the F1F0-ATP synthase exhibited the same tolerances as in the bacterial enzyme. Plasmid shuffling was used for ectopic expression of altered b subunits in a strain carrying a chromosomal disruption of the ATP4 gene. Wild type growth phenotypes were observed for insertions of up to 11 and a deletion of four amino acids on a nonfermentable carbon source. In mitochondria-enriched fractions, abundant ATP hydrolysis activity was seen for the insertion mutants. ATPase activity was largely oligomycin-insensitive in these mitochondrial fractions. In addition, very poor complementation was seen in a mutant with an insertion of 14 amino acids. Lengthier deletions yielded a defective enzyme. The results suggest that although the eukaryotic peripheral stalk is near its minimum length, the b subunit can be extended a considerable distance

Sex differences in congestive markers in patients hospitalized for acute heart failure

Abstract Aims We sought to examine sex differences in congestion in patients hospitalized for acute heart failure (AHF). Understanding congestive patterns in women and men with AHF may provide insights into sex differences in the presentation and prognosis of AHF patients. Methods and results In a prospective, two‐site study in adults hospitalized for AHF, four‐zone lung ultrasound (LUS) was performed at the time of echocardiography at baseline (LUS1) and, in a subset, pre‐discharge (LUS2). B‐lines on LUS and echocardiographic images were analysed offline, blinded to clinical information and outcomes. Among 349 patients with LUS1 data (median age 74, 59% male, and 87% White), women had higher left ventricular ejection fraction (mean 43% vs. 36%, P < 0.001), higher tricuspid annular plane systolic excursion (mean 17 vs. 15 mm, P = 0.021), and higher measures of filling pressures (median E/e′ 20 vs. 16, P < 0.001). B‐line number on LUS1 (median 6 vs. 6, P = 0.69) and admission N‐terminal pro‐B‐type natriuretic peptide levels (median 3932 vs. 3483 pg/mL, P = 0.77) were similar in women and men. In 121 patients with both LUS1 and LUS2 data, there was a similar and significant decrease in B‐lines from baseline to discharge in both women and men. The risk of the composite 90 day outcome increased with higher B‐line number on four‐zone LUS2: unadjusted hazard ratio for each B‐line tertile was 1.86 (95% confidence interval 1.08–3.20, P = 0.025) in women and 1.65 (95% confidence interval 1.03–2.64, P = 0.037) in men (interaction P = 0.72). Conclusions Among patients with AHF, echocardiographic markers differed between women and men at baseline, whereas B‐line number on LUS did not. The dynamic changes in B‐lines during a hospitalization for AHF were similar in women and men

Sex differences in congestive markers in patients hospitalized for acute heart failure

Abstract Aims We sought to examine sex differences in congestion in patients hospitalized for acute heart failure (AHF). Understanding congestive patterns in women and men with AHF may provide insights into sex differences in the presentation and prognosis of AHF patients. Methods and results In a prospective, two‐site study in adults hospitalized for AHF, four‐zone lung ultrasound (LUS) was performed at the time of echocardiography at baseline (LUS1) and, in a subset, pre‐discharge (LUS2). B‐lines on LUS and echocardiographic images were analysed offline, blinded to clinical information and outcomes. Among 349 patients with LUS1 data (median age 74, 59% male, and 87% White), women had higher left ventricular ejection fraction (mean 43% vs. 36%, P < 0.001), higher tricuspid annular plane systolic excursion (mean 17 vs. 15 mm, P = 0.021), and higher measures of filling pressures (median E/e′ 20 vs. 16, P < 0.001). B‐line number on LUS1 (median 6 vs. 6, P = 0.69) and admission N‐terminal pro‐B‐type natriuretic peptide levels (median 3932 vs. 3483 pg/mL, P = 0.77) were similar in women and men. In 121 patients with both LUS1 and LUS2 data, there was a similar and significant decrease in B‐lines from baseline to discharge in both women and men. The risk of the composite 90 day outcome increased with higher B‐line number on four‐zone LUS2: unadjusted hazard ratio for each B‐line tertile was 1.86 (95% confidence interval 1.08–3.20, P = 0.025) in women and 1.65 (95% confidence interval 1.03–2.64, P = 0.037) in men (interaction P = 0.72). Conclusions Among patients with AHF, echocardiographic markers differed between women and men at baseline, whereas B‐line number on LUS did not. The dynamic changes in B‐lines during a hospitalization for AHF were similar in women and men