Biostatistics Commons^™

Variable Selection For Estimating The Optimal Treatment Regimes In The Presence Of A Large Number Of Covariate, Baqun Zhang, Min Zhang

The University of Michigan Department of Biostatistics Working Paper Series

Most of existing methods for optimal treatment regimes, with few exceptions, focus on estimation and are not designed for variable selection with the objective of optimizing treatment decisions. In clinical trials and observational studies, often numerous baseline variables are collected and variable selection is essential for deriving reliable optimal treatment regimes. Although many variable selection methods exist, they mostly focus on selecting variables that are important for prediction (predictive variables) instead of variables that have a qualitative interaction with treatment (prescriptive variables) and hence are important for making treatment decisions. We propose a variable selection method within a general classification …

Practical Targeted Learning From Large Data Sets By Survey Sampling, Patrice Bertail, Antoine Chambaz, Emilien Joly

U.C. Berkeley Division of Biostatistics Working Paper Series

We address the practical construction of asymptotic confidence intervals for smooth (i.e., pathwise differentiable), real-valued statistical
parameters by targeted learning from independent and identically
distributed data in contexts where sample size is so large that it poses
computational challenges. We observe some summary measure of all data and select a sub-sample from the complete data set by Poisson rejective sampling with unequal inclusion probabilities based on the summary measures. Targeted learning is carried out from the easier to handle sub-sample. We derive a central limit theorem for the targeted minimum loss estimator (TMLE) which enables the construction of …

Improved Estimation Of Optimal Cut-Off Point Associated With Youden Index Using Ranked Set Sampling, Jingjing Yin, Hani M. Samawi, Daniel Linder

Biostatistics: Faculty Publications

A diagnostic cut-off point of a biomarker measurement is needed for classifying a random subject to be either diseased or healthy. However, the cut-off point is usually unknown and needs to be estimated by some optimization criteria. One important criterion is the Youden index, which has been widely adopted in practice. The Youden index, which is defined as the maximum of (sensitivity + specificity −1), directly measures the largest total diagnostic accuracy a biomarker can achieve. Therefore, it is desirable to estimate the optimal cut-off point associated with the Youden index. Sometimes, taking the actual measurements of a biomarker is …

Novel Methods For Analyzing Longitudinal Data With Measurement Error In The Time Variable, Caroline Munindi Mulatya

Theses and Dissertations

In some longitudinal studies, the observed time points are often confounded with measurement error due to the sampling conditions, resulting into data with measurement error in the time variable. This type of data occurs mainly in observational studies when the onset of a longitudinal process is unknown or in clinical trials when individual visits do not take place as specified by the study protocol, but are often rounded to coincide with the study protocol. Methodological and inferential implications of error in time varying covariates for both linear and nonlinear models have been studied widely. In this dissertation, we shift attention …

Scalable Collaborative Targeted Learning For High-Dimensional Data, Cheng Ju, Susan Gruber, Samuel D. Lendle, Antoine Chambaz, Jessica M. Franklin, Richard Wyss, Sebastian Schneeweiss, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

Robust inference of a low-dimensional parameter in a large semi-parametric model relies on external estimators of infinite-dimensional features of the distribution of the data. Typically, only one of the latter is optimized for the sake of constructing a well behaved estimator of the low-dimensional parameter of interest. Optimizing more than one of them for the sake of achieving a better bias-variance trade-off in the estimation of the parameter of interest is the core idea driving the C-TMLE procedure.

The original C-TMLE procedure can be presented as a greedy forward stepwise algorithm. It does not scale well when the number $p$ …

Propensity Score Prediction For Electronic Healthcare Databases Using Super Learner And High-Dimensional Propensity Score Methods, Cheng Ju, Mary Combs, Samuel D. Lendle, Jessica M. Franklin, Richard Wyss, Sebastian Schneeweiss, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

The optimal learner for prediction modeling varies depending on the underlying data-generating distribution. Super Learner (SL) is a generic ensemble learning algorithm that uses cross-validation to select among a "library" of candidate prediction models. The SL is not restricted to a single prediction model, but uses the strengths of a variety of learning algorithms to adapt to different databases. While the SL has been shown to perform well in a number of settings, it has not been thoroughly evaluated in large electronic healthcare databases that are common in pharmacoepidemiology and comparative effectiveness research. In this study, we applied and evaluated …

Tmle For Marginal Structural Models Based On An Instrument, Boriska Toth, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

We consider estimation of a causal effect of a possibly continuous treatment when treatment assignment is potentially subject to unmeasured confounding, but an instrumental variable is available. Our focus is on estimating heterogeneous treatment effects, so that the treatment effect can be a function of an arbitrary subset of the observed covariates. One setting where this framework is especially useful is with clinical outcomes. Allowing the causal dose-response curve to depend on a subset of the covariates, we define our parameter of interest to be the projection of the true dose-response curve onto a user-supplied working marginal structural model. We …

Predictors Of Neonatal Abstinence Syndrome In Buprenorphine Exposed Newborn: Can Cord Blood Buprenorphine Metabolite Levels Help?, Darshan Shah, Stacy Brown, Nick Hagemeier, Shimin Zheng, Amy Kyle, Jason Pryor, Nilesh Dankhara, Piyuesh Singh

ETSU Faculty Works

Background

Buprenorphine is a semi-synthetic opioid used for the treatment of opioid dependence. Opioid use, including buprenorphine, has been increasing in recent years, in the general population and in pregnant women. Consequently, there has been a rise in frequency of neonatal abstinence syndrome (NAS), associated with buprenorphine use during pregnancy. The purpose of this study was to investigate correlations between buprenorphine and buprenorphine-metabolite concentrations in cord blood and onset of NAS in buprenorphine exposed newborns.

Methods

Nineteen (19) newborns who met inclusion criteria were followed after birth until discharge in a double-blind non-intervention study, after maternal consent. Cord blood and …

A Powerful Statistical Framework For Generalization Testing In Gwas, With Application To The Hchs/Sol, Tamar Sofer, Ruth Heller, Marina Bogomolov, Christy L. Avery, Mariaelisa Graff, Kari E. North, Alex Reiner, Timothy A. Thornton, Kenneth Rice, Yoav Benjamini, Cathy C. Laurie, Kathleen F. Kerr

UW Biostatistics Working Paper Series

In GWAS, “generalization” is the replication of genotype-phenotype association in a population with different ancestry than the population in which it was first identified. The standard for reporting findings from a GWAS requires a two-stage design, in which discovered associations are replicated in an independent follow-up study. Current practices for declaring generalizations rely on testing associations while controlling the Family Wise Error Rate (FWER) in the discovery study, then separately controlling error measures in the follow-up study. While this approach limits false generalizations, we show that it does not guarantee control over the FWER or False Discovery Rate (FDR) of …

Total Versus Partial Splenectomy In Pediatric Hereditary Spherocytosis: A Systematic Review And Meta-Analysis, Leonardo Guizzetti

Epidemiology and Biostatistics Publications

To compare the clinical effectiveness of total (TS) or partial (PS) splenectomy in pediatric hereditary spherocytosis, a systematic review and meta-analysis was performed (PROSPERO registration CRD42015030056). There were 14 observational studies comparing pre- and post- operative hematologic parameters. Secondary outcomes include in-hospital infections, surgical complications, symptomatic recurrence and biliary disease. TS is more effective than PS to increase hemoglobin (3.6 g/dL vs 2.2 g/dL) and reduce reticulocytes (12.5% vs 6.5%) after one year; outcomes following PS are stable for at least 6 years. There were no cases of overwhelming post-splenectomy sepsis. A population-based patient registry is needed for long-term follow-up.

Dealing With Zero-Numerators In Estimating Drug-Dependence Chances: A Bayesian Approach, Olga A. Vsevolozhskaya, Fernando A. Wagner, James C. Anthony

Biostatistics Presentations

Aims: At CPDD 2015, we applied parametric Hill functions to estimate the probability of drug dependence in relation to the duration of drug-taking experience. A problem we and others have encountered in the estimation of risk of becoming a drug dependence case is an observed point estimate of zero – the so-called “zero-numerator problem.” This problem can be easily observed in certain low risk subgroups even when the sample is large (e.g., the incidence of heroin dependence among 12 year old newly incident heroin users) or with small subgroup sample sizes. In these instances, tan observed zero point estimate …

Mapping Morels: Predicting The Locations Of Morchella Species Through Environmental Factors Using The Gis System, Emily M. Stanevicius

Celebration of Learning

Morel mushrooms, Morechella esculenta and M. deliciosa, are known delicacies across the globe, ranging from exquisite dishes in French cuisine to Eastern palates such as Japanese Matsutake. According to literature, true morels diverged as their own genus about 129 million years, again which has led to the development of more than 177 species and have been part of the human diet since their beginning. However, the elusiveness of morels has contributed to the mushrooms infamy for rarity, and has even been known to sell for more than $40 per pound. This project seeks to aid in the search for morels …

Putting Prep Into Practice: Lessons Learned From Early-Adopting U.S. Providers' Firsthand Experiences Providing Hiv Pre-Exposure Prophylaxis And Associated Care, S. K. Calabrese, Manya Magnus, K. H. Mayer, D. S. Krakower, A. I. Eldahan, L. A. Gaston Hawkins, +5 Additional Authors

Epidemiology Faculty Publications

Optimizing access to HIV pre-exposure prophylaxis (PrEP), an evidence-based HIV prevention resource, requires expanding healthcare providers' adoption of PrEP into clinical practice. This qualitative study explored PrEP providers' firsthand experiences relative to six commonly-cited barriers to prescription-financial coverage, implementation logistics, eligibility determination, adherence concerns, side effects, and anticipated behavior change (risk compensation)-as well as their recommendations for training PrEP-inexperienced providers. U.S.-based PrEP providers were recruited via direct outreach and referral from colleagues and other participants (2014-2015). One-on-one interviews were conducted in person or by phone, transcribed, and analyzed. The sample (n = 18) primarily practiced in the Northeastern (67%) or …

Partner Interfering Behaviors Affecting Cancer Quality Of Life, Ann L. Coker, Diane R. Follingstad, Lisandra S. Garcia, Heather M. Bush

Obstetrics and Gynecology Faculty Publications

Objective: Because partners are an important and unpaid resource in cancer care, understanding how destructive, controlling or interfering partner behaviors influence women's cancer care may be particularly relevant for health care providers seeking to provide cancer care and enhance recovery. Using a new measure of partner interfering behaviors in cancer care (PIB-C), we investigated whether women with a recent cancer diagnosis who additionally endorsed any PIB-C would report (a) more symptoms of depression and stress, and (b) lower Functional Assessment of Cancer Therapy (FACT-G) and lower Functional Assessment of Chronic Illness Therapy-Spiritual Well-being (FACIT-SP) scale scores indicating poorer quality of …

Effect Of Ambient Particulate Matter 2.5 Micrometer (Pm2.5) To Prevalence Of Impaired Lung Function And Asthma In Tangerang And Makassar, Budi Haryanto, Budy Resosoedarmo, Sri Tjahjani Budi Utami, Budi Hartono, Ema Hermawati

Kesmas

Emisi partikel debu 2,5 mikrometer (PM2.5) meningkat dengan bertambahnya jumlah penduduk kota akibat peningkatan angka kendaraan bermotor sebagai transportasi penduduk sehari-hari. Penelitian ini bertujuan untuk mengetahui tingkat gangguan fungsi paru dan asma serta hubungannya dengan kadar ambien PM2.5 pada masyarakat migran di Tangerang dan Makassar dan kondisi sosial ekonomi. Desain potong lintang digunakan dengan melibatkan 4.250 dan 2.900 responden di Tangerang dan Makassar pada bulan April sampai September 2010. Pendekatan cluster sampling diterapkan. Pengukuran ambien PM2.5 di masing-masing kota berdasarkan koordinat 40 lokasi Global Positioning System (GPS). Kadar PM2.5 ditemukan lebih tinggi pada pagi hari dibandingkan siang hari di kedua …

Birth Intervals Among Multiparous Women In Indonesia, Dini Kurniawati, Sabarinah Prasetyo

Kesmas

Angka kematian ibu dan angka kematian bayi di Indonesia masih tinggi. Salah satu faktor yang menyebabkan tingginya risiko kematian pada ibu dan bayi adalah kelahiran terlalu dekat. Penelitian ini bertujuan untuk mempelajari determinan jarak antarkelahiran pada perempuan multipara di Indonesia. Penelitian ini menggunakan data Survei Demografi Kesehatan Indonesia tahun 2012 pada 9.945 perempuan multipara. Analisis data menggunakan uji Mann Whitney, Kruskal Wallis, dan regresi logistik. Median jarak antarkelahiran sebesar 62 bulan dan 22,8% perempuan memiliki jarak antarkelahiran kurang dari tiga tahun. Hasil menunjukkan determinan jarak antarkelahiran pendek meliputi pendidikan ibu, usia terakhir melahirkan, ukuran ideal keluarga, pemakaian kontrasepsi, riwayat kematian …

Child Health Improvement Through Implementation Of Food Safety Model, Arief Safari, Machfud Machfud, Eriyatno Eriyatno, Heny Kuswanti Daryanto

Kesmas

Pemenuhan akan pangan merupakan komponen dasar untuk mewujudkan sumber daya manusia yang berkualitas. Namun, masih terdapat permasalahan dalam mewujudkannya, di antaranya masalah keamanan pangan dengan persentase kasus keracunan makanan masih tinggi. Penelitian ini bertujuan untuk menganalisis situasi pelaksanaan keamanan Pangan Jajanan Anak Sekolah (PJAS) yang ada saat ini dan memilih alternatif model keamanan pangan yang paling efektif dan efisien diterapkan di usaha mikro kecil (UMK) guna meningkatkan keamanan pangan yang dihasilkannya sehingga terjadi peningkatan kesehatan anak. Penelitian dilakukan pada kuartal II tahun 2015 sampai dengan awal kuartal III tahun 2015 melalui survei lapangan dan survei pakar dengan mengambil studi kasus …

Housewives’ Compliance In Reading Food Labels In Gorontalo City, Imran Tumenggung, Lucky Herawati, Sofyawati Talibo

Kesmas

Di Indonesia, masalah label pada kemasan makanan kurang mendapat perhatian konsumen. Penelitian ini bertujuan untuk mempelajari determinan kepatuhan membaca label pada kemasan makanan oleh ibu rumah tangga di Kota Gorontalo. Penelitian dengan metode survei ini dilakukan dari bulan Juni sampai Agustus 2013. Data dikumpulkan secara potong lintang dengan menggunakan angket. Variabel terikat adalah kepatuhan membaca label pada kemasan makanan yang terdiri dari label informasi nilai gizi, komposisi makanan, masa kedaluwarsa, harga, dan status halal. Variabel bebas adalah usia, tingkat pendidikan, dan keterpaparan dengan media informasi. Besar sampel 262 orang ditentukan secara accidental technique. Analisis data menggunakan uji kai kuadrat. Hasil …

Husband’S Support Towards Unmet Need Of Hiv Positive-Infected Women Of Childbearing Age, Sophia Sophia, Anita Deborah Anwar, Bony Wiem Lestari

Kesmas

Jutaan wanita usia subur (WUS) dengan HIV positif di negara berkembang saat ini tidak menggunakan kontrasepsi untuk menunda atau mengakhiri kehamilan. Pencegahan kehamilan yang tidak diinginkan pada WUS dengan HIV positif sangat penting untuk meningkatkan kualitas hidup ibu dan anak. Tujuan penelitian ini untuk menganalisis faktor-faktor yang berpengaruh terhadap unmet need pada WUS dengan HIV positif. Metode penelitian adalah cross sectional dengan sampel berjumlah 130 WUS dengan HIV positif yang diambil secara consecutive sampling. Penelitian dilakukan pada 24 Maret - 30 Juni 2015 di Klinik Mawar Kota Bandung. Pengumpulan data dilakukan melalui wawancara dengan menggunakan kuesioner, kemudian data dianalisis dengan …

Impact Of Husband’S Participation In Antenatal Care On The Use Of Skilled Birth Attendant, Febri Wicaksono

Kesmas

Pendekatan alternatif diperlukan untuk mengatasi persoalan kesehatan reproduksi, salah satunya dengan meningkatkan partisipasi laki-laki pada kesehatan reproduksi perempuan. Penelitian ini bertujuan untuk menelusuri dampak partisipasi suami dalam pelayanan antenatal pada penggunaan tenaga persalinan terlatih setelah mengontrol karakteristik sosial demografi. Sampel sebanyak 4.000 perempuan berusia 15 – 49 tahun yang memiliki persalinan terakhir pada tahun lalu sebelum survei diambil dari Survei Demografi dan Kesehatan Indonesia tahun 2012. Penelitian menggunakan model regresi logistik biner untuk mengidentifikasi dampak partisipasi suami dalam pelayanan antenatal pada penggunaan tenaga persalinan terlatih setelah mengontrol karakteristik ibu dan sosial demografi. Peluang setelah mengontrol faktor lainnya mengindikasikan perempuan yang …