Peer-Reviewed Publications
[2020] Evaluating Diabetic Retinopathy Screening Interventions in a Microsimulation Model
2020 Winter Simulation Conference (WSC)
Authors: Breanna Swan, Siddhartha Nambiar, Priscille Koutouan, Maria E. Mayorga, Julia Ivy, Stephen Fransen
About: We developed a microsimulation integrating the natural history model of diabetic retinopathy (DR) with a patient’s interaction with the care system. We introduced a DR screening device in primary care, with and without care coordination by a medical professional, in two interventions to the current care path. We found the interventions increased adherence of patients with vision-threatening DR (VTDR) to follow-up eye care, decreased the number of ‘unnecessary’ visits in specialty eye care from patients without VTDR, and decreased the total years spent blind.
[2020] Improving Hospital Operational Efficiency when Staff Workload Affects Patient Outcomes
Dissertation | North Carolina State University
Authors: Siddhartha Nambiar
About: In this dissertation, I aimed to improve hospital operational efficiency by developing a set of models that optimize different decisions within the health care process, such as patient flow and resource utilization. In developing these models, I proposed incorporating features unique to healthcare systems that make the models better abstractions of reality. These features include the use of nurse workload to affect patient outcomes, the use of floating nurses to handle abrupt variation in demand, and the pooling of resources within a hospital unit to care for the patients within the unit.
[2020] Objective measures of workload in healthcare: a narrative review
International Journal of Health Care Quality Assurance
Authors: Daniela Fishbein, Siddhartha Nambiar, Kendall McKenzie, Maria Mayorga, Kristen Miller, Kevin Tran, Laura Schubel, Joseph Agor, Tracy Kim, Muge Capan
About: Workload is a critical concept in the evaluation of performance and quality in healthcare systems, but its definition relies on the perspective (e.g. individual clinician-level vs unit-level workload) and type of available metrics (e.g. objective vs subjective measures). The purpose of this paper is to provide an overview of objective measures of workload associated with direct care delivery in tertiary healthcare settings, with a focus on measures that can be obtained from electronic records to inform operationalization of workload measurement.
[2019] Mailed FIT (fecal immunochemical test), navigation or patient reminders? Using microsimulation to inform selection of interventions to increase colorectal cancer screening in Medicaid enrollees
Preventive Medicine
Authors: Melinda M Davis, Siddhartha Nambiar, Maria E Mayorga, Eliana Sullivan, Karen Hicklin, Meghan C O’Leary, Kristen Dillon, Kristen Hassmiller Lich, Yifan Gu, Bonnie K Lind, Stephanie B Wheeler
About: We used microsimulation to project CRC screening patterns, CRC cases averted, and life-years gained in the population of 68,077 Oregon Medicaid enrollees 50–64 over a five year period starting in January 2019. The simulation estimated the cost-effectiveness of five intervention scenarios - academic detailing plus provider audit and feedback (Detailing+), patient reminders (Reminders), mailing a Fecal Immunochemical Test (FIT) directly to the patient’s home (Mailed FIT), patient navigation (Navigation), and mailed FIT with Navigation (Mailed FIT+Navigation) – compared to usual care. Over a five year period, Reminders, Mailed FIT and Mailed FIT+Navigation were expected to be cost effective if stakeholders were willing to pay $230 or less per additional year up-to-date (at a cost of $22, $59, and $227 respectively), whereas Detailing+ and Navigation were more costly for the same benefits.
[2019] Estimating the impact of insurance expansion on colorectal cancer and related costs in North Carolina: A population-level simulation analysis
Preventive Medicine
Authors: Kristen Hassmiller Lich, Meghan C O’Leary, Siddhartha Nambiar, Rachel M Townsley, Maria E Mayorga, Karen Hicklin, Leah Frerichs, Paul R Shafer, Melinda M Davis, Stephanie B Wheeler
About: We simulated the full lifetime of a synthetic population of 3,298,265 residents age-eligible for CRC screening (ages 50–75) during a 5-year period starting January 1, 2018, including polyp incidence and progression and CRC screening, diagnosis, treatment, and mortality. Insurance scenarios included: status quo, which in NC includes access to the Health Insurance Exchange (HIE) under the Affordable Care Act (ACA); no ACA; NC Medicaid expansion, and Medicare-for-all. The insurance expansion scenarios would increase percent up-to-date with screening by 0.3 and 7.1 percentage points for Medicaid expansion and Medicare-for-all, respectively, while insurance reduction would reduce percent up-to-date by 1.1 percentage points, compared to the status quo (51.7% up-to-date), at the end of the 5-year period.
[2018] A Simulation Model To Assess The Impact Of Insurance Expansion On Colorectal Cancer Screening At The Population Level
2018 Winter Simulation Conference (WSC)
Authors: Siddhartha Nambiar, Maria E Mayorga, Meghan C O’Leary, Kristen Hassmiller Lich, Stephanie B Wheeler
About: In this work, we present the development of an individual-based discrete-event simulation model to estimate the impact of insurance expansion scenarios on CRC screening, incidence, mortality, and costs. A national repeated cross-sectional survey was used to estimate which individuals obtained insurance in North Carolina (NC) after the Affordable Care Act (ACA). The potential impact of expanding the state’s Medicaid program is tested and compared to no insurance reform and the ACA without Medicaid expansion.
[2018] On scheduling a photolithography area containing cluster tools
Computers & Industrial Engineering
Authors: Sreenath Chalil Madathil, Siddhartha Nambiar, Scott J Mason, Mary E Kurz
About: In this paper, we present a model for optimizing the scheduling of the photolithography process in the presence of both individual and cluster tools. The combination of these individual and cluster tools that process various layers (stages) of the semiconductor manufacturing process flow is a special type of flexible flowshop. We seek separately to minimize total weighted completion time and maximize on-time delivery performance. Experimental results suggest that our solution algorithms show promise for real world implementation as they can help to improve resource utilization, reduce job completion times, and decrease unnecessary delays in a wafer fab.
[2016] Low-cost sensor system design for in-home physical activity tracking
IEEE journal of translational engineering in health and medicine
Authors: Siddhartha Nambiar, Alexander Nikolaev, Melissa Greene, Lora Cavuoto, Ann Bisantz
About: This research uses simulation, optimization, and regression analyses to assess the feasibility of using a small number of sensors to track movement and infer physical activity levels of older adults. Based on activity data from the American Time Use Survey and assisted living apartment layouts, we determined that using three to four doorway sensors can be used to effectively capture a sufficient amount of movements in order to estimate activity. The research also identified preferred approaches for assigning sensor locations, evaluated the error magnitude inherent in the approach, and developed a methodology to identify which apartment layouts would be best suited for these technologies.
[2016] Towards evaluating and enhancing the reach of online health forums for smoking cessation
Network Modeling Analysis in Health Informatics and Bioinformatics
Authors: Michael Stearns, Siddhartha Nambiar, Alexander Nikolaev, Alexander Semenov, Scott McIntosh
About: This paper quantitatively studies the effect of engagement on the users of the Alt.Support.Stop-Smoking forum that served the needs of an online smoking cessation community for more than 10 years. The paper then demonstrates how online service evaluation and planning by social network analysts can be applied towards strategic interventions targeting increased user engagement in online health forums.