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Browsing by Author "Xiao, Shan"
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Item Bayesian design and analysis of cluster randomized trials(2017-08-07) Xiao, Shan; Tu, Wanzhu; Liu, ZiyueCluster randomization is frequently used in clinical trials for convenience of inter ventional implementation and for reducing the risk of contamination. The opera tional convenience of cluster randomized trials, however, is gained at the expense of reduced analytical power. Compared to individually randomized studies, cluster randomized trials often have a much-reduced power. In this dissertation, I consider ways of enhancing analytical power with historical trial data. Specifically, I introduce a hierarchical Bayesian model that is designed to incorporate available information from previous trials of the same or similar interventions. Operationally, the amount of information gained from the previous trials is determined by a Kullback-Leibler divergence measure that quantifies the similarity, or lack thereof, between the histor ical and current trial data. More weight is given to the historical data if they more closely resemble the current trial data. Along this line, I examine the Type I error rates and analytical power associated with the proposed method, in comparison with the existing methods without utilizing the ancillary historical information. Similarly, to design a cluster randomized trial, one could estimate the power by simulating trial data and comparing them with the historical data from the published studies. Data analytical and power simulation methods are developed for more general situations of cluster randomized trials, with multiple arms and multiple types of data following the exponential family of distributions. An R package is developed for practical use of the methods in data analysis and trial design.Item An Educational Intervention to Improve HPV Vaccination: A Cluster Randomized Trial(AAP, 2019-01) Dixon, Brian E.; Zimet, Gregory D.; Xiao, Shan; Tu, Wanzhu; Lindsay, Brianna; Church, Abby; Downs, Stephen M.; Epidemiology, School of Public HealthBackground: Human Papillomavirus (HPV) infection can lead to serious health issues and remains the most common sexually transmitted infection. Despite availability of effective vaccines, HPV vaccination rates are suboptimal. Methods: In a cluster randomized trial, an intervention targeting parents of adolescents (11-17 years) eligible for a dose of HPV vaccine was tested in pediatric clinics part of an urban health system. Parents watched a digital video outlining the risks and benefits of vaccine using a tablet in the exam room. The primary outcome was change in HPV vaccine status two weeks after the clinic visit. An intention to treat analysis for the primary outcome utilized generalized estimating equations to accommodate the potential cluster effect of clinics. Results: A total of 1596 eligible adolescents were observed during the 7-month trial. One-third of adolescents visited an intervention clinic. Adolescents who attended an intervention clinic were more likely to be younger (11-12 years) than those who attended a control clinic (72.4% versus 49.8%; p<0.001). No differences in race or gender were observed. The proportion of adolescents with an observed change in vaccine status was higher for those attending an intervention clinic (64.8%) versus control clinic (50.1%; OR=1.82; 95% CI=1.47-2.25; p<0.001). Adolescents whose parents watched the video had a three times greater odds of receiving a dose of the HPV vaccine (78.0%; OR=3.07; 95% CI=1.47-6.42; p=0.003). Conclusions: Educational interventions delivered within a clinical setting hold promise to improve vaccination behaviors.Item Simple and Elaborated Clinician Reminder Prompts for Human Papillomavirus Vaccination: A Randomized Clinical Trial(Elsevier, 2018-03) Zimet, Gregory D.; Dixon, Brian E.; Xiao, Shan; Tu, Wanzhu; Kulkarni, Amit; Dugan, Tamara; Sheley, Meena; Downs, Stephen M.; Pediatrics, School of MedicineObjective To evaluate the effects of simple and elaborated health care provider (HCP) reminder prompts on human papillomavirus (HPV) vaccine initiation rates. Methods Twenty-nine pediatric HCPs serving 5 pediatric clinics were randomized to 1 of 3 arms: 1) usual practice control, 2) simple reminder prompt, and 3) elaborated reminder prompt, which included suggested language for recommending the early adolescent platform vaccines. Prompts were delivered via a computer-based clinical decision support system deployed in the 5 clinics. Eligible patients were ages 11 to 13 years, had not received HPV vaccine, and were due for meningococcal ACWY (MenACWY) vaccine and/or the tetanus, diphtheria, and pertussis booster (Tdap). Receipt of HPV vaccine was determined via automated queries sent to the Indiana immunization registry. Data were analyzed via logistic regression models, with generalized estimating equations used to account for the clustering of patients within HCPs. Results Ten HCPs in the control group saw 301 patients, 8 HCPs in the simple prompt group saw 124, and 11 HCPs in the elaborated prompt group saw 223. The elaborated prompt arm had a higher rate of HPV vaccination (62%) than the control arm (45%): adjusted odds ratio, 2.76; 95% confidence interval, 1.07 to 7.14. The simple prompt arm did not differ significantly from the control arm with respect to HPV vaccine initiation, which might have been because of the small sample size for this arm. MenACWY and Tdap rates did not vary across the 3 arms. Conclusions Results suggest that an elaborated HCP-targeted reminder prompt, with suggested recommendation language, might improve rates of HPV vaccine initiation.