- Browse by Author
Browsing by Author "Lourens, Spencer"
Now showing 1 - 10 of 15
Results Per Page
Sort Options
Item Acute Alcoholic Hepatitis: Natural History and Predictors of Mortality Using a Multicenter Prospective Study(Elsevier, 2017-04-28) Lourens, Spencer; Sunjaya, Dharma B.; Singal, Ashwani; Liangpunsakul, Suthat; Puri, Puneet; Sanyal, Arun; Ren, Xiaowei; Gores, Gregory J.; Radaeva, Svetlana; Chalasani, Naga; Crabb, David W.; Katz, Barry; Kamath, Patrick S.; Shah, Vijay H.; Biostatistics, School of Public HealthObjective: To examine the natural history of acute alcoholic hepatitis (AH) and identify predictors of mortality for AH using data from a prospective multicenter observational study. Participants and Methods: We analyzed data from 164 patients with AH and 131 heavy-drinking controls with no liver disease. Participants underwent clinical/laboratory assessment at baseline and 6 and 12 months after enrollment. Multivariable analyses were conducted to identify variables associated with mortality and examine the association between coffee drinking and risk of AH. Results: Thirty-six patients with AH died during follow-up, with estimated 30-day, 90-day, 180-day, and 1-year survival of 0.91 (95% CI, 0.87-0.96), 0.85 (95% CI, 0.80-0.91), 0.80 (95% CI, 0.74-0.87), and 0.75 (95% CI, 0.68-0.83), respectively. In the multivariable analysis, higher serum bilirubin level (hazard ratio [HR]=1.059; 95% CI, 1.022-1.089), lower hemoglobin level (HR=1.263; 95% CI, 1.012-1.575), and lower platelet count (HR=1.006; 95% CI, 1.001-1.012) were independently associated with mortality in AH. Compared with controls, fewer patients with AH regularly consumed coffee (20% vs 44%; P<.001), and this association between regular coffee drinking and lower risk of AH persisted after controlling for relevant covariates (odds ratio=0.26; 95% CI, 0.15-0.46). Time-dependent receiver operating characteristic curve analysis revealed that Model for End-Stage Liver Disease; Maddrey Discriminant Function; age, serum bilirubin, international normalized ratio, and serum creatinine; and Child-Pugh scores all provided similar discrimination performance at 30 days (area under the curve=0.73-0.77). Conclusion: Alcoholic hepatitis remains highly fatal, with 1-year mortality of 25%. Regular coffee consumption was associated with lower risk of AH in heavy drinkers.Item Analysis of longitudinal censored semicontinuous data with application to the study of executive dysfunction: the Towers Task(Sage, 2017) Lourens, Spencer; Zhang, Ying; Long, Jeffrey D.; Paulsen, Jane S.; Biostatistics and Health Data Science, School of MedicineExecutive dysfunction is a deficiency in skills of planning and problem solving that characterizes many neuropsychiatric disorders. The Towers Task is a commonly used measure of planning and problem solving for assessing executive function. Towers Task data are usually zero-inflated and right-censored, and ignoring these features can result in biased inference for the disease characterization of executive dysfunction. In this manuscript, a mixed-effects model for longitudinal censored semicontinuous data is developed for analyzing longitudinal Towers Task data from the PREDICT-HD study. The model is contrasted with current practice and implications for general use are discussed.Item Assessing Depression Improvement with the Remission Evaluation and Mood Inventory Tool (REMIT)(Elsevier, 2019-09) Bushey, Michael A.; Kroenke, Kurt; Baye, Fitsum; Lourens, Spencer; Psychiatry, School of MedicineObjective The Remission Evaluation and Mood Inventory Tool (REMIT) was developed as a brief complementary measure to provide a more robust assessment of depression improvement than tracking DSM-V symptom improvement alone. This study provides further validation of the REMIT tool and examines its utility in predicting depression improvement. Methods The sample comprised 294 primary care patients enrolled in a telecare trial of pain plus depression and/or anxiety. Assessments collected included: REMIT, PHQ-9 and measures assessing anxiety, pain, sleep, fatigue, somatization, health-related quality of life and disability. Data was analyzed to assess the REMIT's validity, its minimally important difference (MID), and its utility in predicting 6-month depression improvement. Results Convergent and construct validity of REMIT was supported by moderate correlations with mental health measures and weaker correlation with physical health measures. MID of approximately 2 points for REMIT was estimated by two metrics: 0.5 standard deviation and 1 standard error of measurement. Both baseline and 3-month change in REMIT scores predicted depression improvement at 6 months. Indeed, REMIT was as good or better predictor than the PHQ-9. Conclusion The REMIT measure is a brief 5-item tool that augments core DSM-V symptom-oriented metrics in assessing and predicting recovery from major depression.Item Challenges in Patient Enrollment and Retention in Clinical Studies for Alcoholic Hepatitis: Experience of the TREAT Consortium(Wiley, 2017) Comerford, Megan; Lourens, Spencer; Liangpunsakul, Suthat; Chalasani, Naga P.; Sanyal, Arun J.; Shah, Vijay H.; Kamath, Patrick S.; Puri, Puneet; Katz, Barry P.; Radaeva, Svetlana; Crabb, David W.; Medicine, School of MedicineThe TREAT Consortium has carried out clinical studies on alcoholic hepatitis (AH) for over 4 years. We encountered problems with participant recruitment, retention, and eligibility for specific protocols. To improve our ability to carry out such trials, we reviewed recruitment screening logs, end of study logs, and surveyed study coordinators to learn the reasons for missing patients, why patients declined enrollment, and the number of patients eligible for treatment trials. Associations of the recruited subjects’ demographics with their adherence to follow-up appointments were examined. Three hundred eight-seven patients (AH and heavy drinking controls) were enrolled in the observational study, and 55 AH patients were recruited into treatment trials. About half of patients identified with AH could not be recruited; no specific reason could be determined for about two-thirds of these. Among the patients who gave a reason for not participating, the most common reasons were feeling too sick to participate, desire to concentrate on abstinence, and lack of interest in research. Approximately a quarter of the AH patients met eligibility criteria for treatment trials for moderate or severe AH and we were able to recruit half to two-thirds of those eligible. Approximately 35% of participants in the observational study returned for both 6- and 12-month follow-up visits. We did not identify biopsychosocial or demographic correlates of retention in the study. This analysis revealed that attempts at recruitment into trials for AH miss some subjects because of structural issues surrounding their hospital admission, and encounter a high rate of patient refusal to participate. Nonetheless, more than half of the patients who met the eligibility criteria for moderate or severe AH were entered into clinical trials. Retention rates for the observational study are relatively low. These findings need to be accounted for in clinical trial design and power analysis.Item A clinical trial method to show delay of onset in Huntington disease(Wiley, 2019-02) Paulsen, Jane S.; Lourens, Spencer; Kieburtz, Karl; Zhang, Ying; Biostatistics, School of Public HealthBackground: Disease-modifying clinical trials in persons without symptoms are often limited in methods to assess the impact associated with experimental therapeutics. This study suggests sample enrichment approaches to facilitate preventive trials to delay disease onset in individuals with the dominant gene for Huntington disease. Methods: Using published onset prediction indexes, we conducted the receiver operating curve analysis for diagnosis within a 3-year clinical trial time frame. We determined optimal cut points on the indexes for participant recruitment and then conducted sample size and power calculations to detect varying effect sizes for treatment efficacy in reducing 3-year rates of disease onset (or diagnosis). Results: Area under the curve for 3 onset prediction indexes all demonstrated excellent value in sample enrichment methodology, with the best-performing index being the multivariate risk score (MRS). Conclusions: This study showed that conducting an intervention trial in premanifest and prodromal individuals with the gene expansion for Huntington disease is highly feasible using sample enrichment recruitment methods. Ongoing natural history studies are highly likely to indicate additional markers of disease prior to diagnosis. Statistical modeling of identified markers can facilitate participant enrichment to increase the likelihood of detecting a difference between treatment arms in a cost-effective and efficient manner. Such variations may expedite translation of emerging therapies to persons in an earlier phase of the disease.Item Comparing the Patient Health Questionnaire – 15 and the Somatic Symptom Scale – 8 as measures of somatic symptom burden(Elsevier, 2017-10) Toussaint, Anne; Kroenke, Kurt; Baye, Fitsum; Lourens, Spencer; Department of Medicine, School of MedicinePurpose The Patient Health Questionnaire – 15 (PHQ-15) and the Somatic Symptom Scale – 8 (SSS-8) are self-report measures which assess somatic symptom burden. The present study investigates whether the two measures are comparable in terms of their psychometric properties and estimates of symptom burden. Method Item characteristics, reliability, symptom severity and construct validity with regard to other relevant psychological, health-related quality of life and disability measures were compared for the PHQ-15m and the SSS-8 in 294 primary care patients who participated in a randomized comparative effectiveness trial targeting pain and mood symptoms. Results The reliabilities of the PHQ-15m and the SSS-8 were α = 0.66 and α = 0.72, respectively. Both measures were highly correlated (r = 0.79). All item characteristics were comparable and both instruments showed the same pattern of correlations with instruments measuring depression, anxiety, pain, quality of life and impairment (r = 0.25 to 0.53). A 1-point score increase (worsening of somatic symptoms) on either instrument resulted in a 3.7% to 3.9% increase in the number of disability days reported for the last four weeks. Using the same severity thresholds (5: low, 10: medium, 15: high), both measures identified nearly identical subgroups of patients with regard to health-related quality of life and disability. Conclusion The PHQ-15m and the SSS-8 are comparable measures in terms of reliability and validity and severity classifications. These findings are in line with previous results and support the use of the SSS-8 as a valuable and short alternative to the original PHQ-15 in settings with limited assessment time.Item Comparison of nonlinear curves and surfaces(Elsevier, 2020-10) Zhao, Shi; Bakoyannis, Giorgos; Lourens, Spencer; Tu, Wanzhu; Biostatistics, School of Public HealthEstimation of nonlinear curves and surfaces has long been the focus of semiparametric and nonparametric regression analysis. What has been less studied is the comparison of nonlinear functions. In lower-dimensional situations, inference typically involves comparisons of curves and surfaces. The existing comparative procedures are subject to various limitations, and few computational tools have been made available for off-the-shelf use. To address these limitations, two modified testing procedures for nonlinear curve and surface comparisons are proposed. The proposed computational tools are implemented in an R package, with a syntax similar to that of the commonly used model fitting packages. An R Shiny application is provided with an interactive interface for analysts who do not use R. The new tests are consistent against fixed alternative hypotheses. Theoretical details are presented in an appendix. Operating characteristics of the proposed tests are assessed against the existing methods. Applications of the methods are illustrated through real data examples.Item Composite measures of pain, anxiety, and depressive (PAD) symptoms: Construct and predictive validity(Elsevier, 2021-09) Bushey, Michael A.; Kroenke, Kurt; Baye, Fitsum; Lourens, Spencer; Psychiatry, School of MedicineObjective Pain, anxiety, and depression (PAD) are common, co-occurring symptoms that adversely affect one another and may respond to common treatments. PAD composite measures would be useful for tracking treatment response in patients with PAD symptoms. The goal of this study is to compare 3 different PAD composite scales in terms of construct validity, responsiveness, and utility in predicting global improvement. Method The sample consisted of 294 primary care patients enrolled in a telecare trial for treating pain, anxiety, and depression. Assessments at baseline and 3 months included the Brief Pain Inventory, PHQ-9 depression scale, GAD-7 anxiety scale, PROMIS measures, Medical Outcomes Study Short-Form items, disability measures, and patient-reported global improvement. Construct validity of the PAD composite measures, their responsiveness, and their ability to predict global improvement was analyzed using Pearson correlations, standardized response means, and receiver operating characteristics analysis. Results PAD composite measures correlated strongly with one another, and moderately with measures of function, vitality, and disability. Each PAD composite measure demonstrated similar responsiveness in detecting improvement at 3 months as assessed by standardized response means (SRMs) and area under the curve (AUC analyses).The SRMs for partial and substantial global improvement corresponded to moderate (Cohen's d of 0.58 to 0.69) and large (0.81 to 0.93) effect sizes, respectively. Conclusions Three different PAD composite measures demonstrate good construct validity as well as responsiveness in detecting global improvement of pain, anxiety and depression at 3 months.Item The Great One Is Born: Wayne Gretzky's Monumental Season(2019-05) Ison, Tyler; Fadel, William; Lourens, Spencer; Zhang, YingStatistics and athletic sports have always had a strong connection that many critics, fans and statisticians utilize to determine how successful a team or an individual player might be over an entire season or even throughout one’s career. The success of a player or team is often characterized by investigating the consistency that has been shown throughout the season or career, which has led to more investigation of the streakiness of players. Studies have been done to examine great streaks, such as Joe DiMaggio’s 56 game hitting streak or Tiger Woods’ 142 consecutive cuts made streak, but what about the outstanding streak that occurred during the 1983-1984 NHL season? Wayne Gretzky, of the Edmonton Oilers, managed to showcase just how elite he was as a playmaker during that season. Gretzky produced a remarkable 51-game point streak, in which he recorded at least one goal or point in 51 consecutive games; a streak that has not received the recognition that it deserves. Using game-by-game data for the entire 1983-1984 NHL season for all players, the research looks at not only the evaluation of Gretzky’s streak, but also compares his production and streak to the remainder of the league. Gretzky demonstrated why he is one of the greatest players to ever step foot on the ice, and his elite status is shown throughout this analysis. Comparing Gretzky’s streak to that of DiMaggio’s was shown to be a little challenging but, some general conclusions were made based on the comparison of analyses that were performed; but without the proper statistics being readily available, it is hard to adequately dictate which streak is ultimately more impressive or more rare.Item Integrating Data Science into T32 Training Programs at IUPUI(2019-06-30) Dixon, Brian E.; Stumpff, Julia C.; Kasthurirathne, Suranga N.; Lourens, Spencer; Janga, Sarath; Liu, Yunlong; Huang, KunData science is critically important to the biomedical research enterprise. Many research efforts currently and in the future will employ advanced computational techniques to analyze extremely large datasets in order to discover insights relevant to human health. Therefore the next generation of biomedical scientists requires knowledge of and proficiency in data science. With support from the U.S. National Library of Medicine, a team of faculty from Indiana University-Purdue University Indianapolis (IUPUI) facilitated curricula enhancement for National Institutes of Health (NIH) T32 research training programs with respect to data science. In collaboration with the existing NIH T32 Program Directors at IUPUI and the IU School of Medicine, the interdisciplinary team of faculty drawn from multiple schools and departments examined the existing landscape of data science offerings on campus in parallel with an assessment of the competencies that future biomedical and clinician scientists will require to be comfortable using data science methods to advance their research. The IUPUI campus possesses a rich tapestry of data science education programs across multiple schools and departments. Furthermore, the campus is home to more than a dozen world-class T32 programs funded by the NIH to train biomedical and clinician scientists. However, existing training programs do not currently emphasize data science or provide specific curriculum designed to ensure T32 graduates possess basic competencies in data science. To position the campus for the future, robust T32 programs need to connect with the rapidly growing data science programs. This report summarizes the rationale for the importance of connection and the competencies that future biomedical and clinical scientists will require to be successful. The report further describes the curriculum mapping efforts to link competencies with available degree programs, courses and workshops on campus. The report further recommends next steps for campus leadership, including but not limited to T32 Program Directors, the Office of the Vice Chancellor for Research, the Executive Associate Dean for Research Affairs at the IU School of Medicine, and the President and CEO of the Regenstrief Institute. Together we can strengthen the IUPUI campus and help ensure its T32 graduates are successful in their research careers.