@article{nambiar_mayorga_liu_2023, title={Routing and staffing in emergency departments: A multiclass queueing model with workload dependent service times}, volume={13}, ISSN={["2472-5587"]}, DOI={10.1080/24725579.2022.2100522}, abstractNote={Abstract Efficient patient flow through an emergency department is a critical factor that contributes to a hospital’s performance, which influences overall patient health outcomes. In this work, we model a multiclass multiserver queueing system where patients of varying acuity receive care from one of several wards, each ward is attended by several nurses who work as a team. Supported by empirical evidence that a patient’s time-in-ward is a function of the nurse-patient ratio in that ward, we incorporate state-dependent service times into our model. Our objective is to reduce patient time in system and to control nurse workload by jointly optimizing patient routing and nurse allocation decisions. Due to the computational challenges in formulating and solving the queueing model representation, we study a corresponding deterministic fluid model which serves as a first-order approximation of the multiclass queueing model. Next, we formulate and solve an optimization model using the first-order control equations and input the results into a discrete-event simulation to estimate performance measures, such as patient length-of-stay and ward workload. Finally, we present a case study using retrospective data from a real hospital which highlights the importance of accounting for nurse workload and service behavior in developing routing and staffing policies.}, number={1}, journal={IISE TRANSACTIONS ON HEALTHCARE SYSTEMS ENGINEERING}, author={Nambiar, Siddhartha and Mayorga, Maria E. and Liu, Yunan}, year={2023}, month={Jan}, pages={46–61} }
 @article{khasawneh_madathil_taaffe_zinzow_ponathil_madathil_nambiar_nanda_rosopa_2022, title={Dynamic simulation of social media challenge participation to examine intervention strategies}, volume={9}, ISSN={["2432-2725"]}, DOI={10.1007/s42001-022-00183-7}, journal={JOURNAL OF COMPUTATIONAL SOCIAL SCIENCE}, author={Khasawneh, Amro and Madathil, Kapil Chalil and Taaffe, Kevin M. and Zinzow, Heidi and Ponathil, Amal and Madathil, Sreenath Chalil and Nambiar, Siddhartha and Nanda, Gaurav and Rosopa, Patrick J.}, year={2022}, month={Sep} }
 @article{swan_nambiar_koutouan_mayorga_ivy_fransen_2020, title={EVALUATING DIABETIC RETINOPATHY SCREENING INTERVENTIONS IN A MICROSIMULATION MODEL}, ISSN={["0891-7736"]}, DOI={10.1109/WSC48552.2020.9384074}, abstractNote={Diabetic retinopathy (DR) is the leading cause of blindness for working age Americans. Early detection, timely treatment, and appropriate follow-up care reduce the risk of severe vision loss from DR by 95%, yet, less than 50% of people with diabetes adhere to the recommended screening guidelines. Diabetes is a complicated disease for patients and their physicians to manage. We developed a microsimulation integrating the natural history model of 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.}, journal={2020 WINTER SIMULATION CONFERENCE (WSC)}, author={Swan, Breanna and Nambiar, Siddhartha and Koutouan, Priscille and Mayorga, Maria E. and Ivy, Julie and Fransen, Stephen}, year={2020}, pages={944–955} }
 @inproceedings{a simulation model to assess the impact of insurance expansion on colorectal cancer screening at the population level_2019, volume={2018-December}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85062602689&partnerID=MN8TOARS}, DOI={10.1109/WSC.2018.8632261}, abstractNote={Recent health care reform debates have triggered substantial discussion on how best to improve access to insurance. Colorectal cancer (CRC) is an example of a largely preventable condition, if access to and use of healthcare is increased. Early and ongoing screening and intervention can identify and remove polyps before they become cancerous. 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. The model integrates a census-based synthetic population, national data, claims based statistical models, and a natural history module in which simulated polyps and cancer progress.}, booktitle={Proceedings - Winter Simulation Conference}, year={2019}, pages={2701–2712} }
 @article{lich_meghan c. o'leary_nambiar_townsley_mayorga_hicklin_frerichs_shafer_davis_wheeler_2019, title={Estimating the impact of insurance expansion on colorectal cancer and related costs in North Carolina: A population-level simulation analysis}, volume={129}, ISSN={["1096-0260"]}, url={http://dx.doi.org/10.1016/j.ypmed.2019.105847}, DOI={10.1016/j.ypmed.2019.105847}, abstractNote={Although screening is effective in reducing incidence, mortality, and costs of treating colorectal cancer (CRC), it remains underutilized, in part due to limited insurance access. We used microsimulation to estimate the health and financial effects of insurance expansion and reduction scenarios in North Carolina (NC). We simulated the full lifetime of a simulated 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. Throughout these individuals' lifetimes, this change in CRC screening/testing results in an estimated 498 CRC cases averted with Medicaid expansion and 6031 averted with Medicare-for-all, and an additional 1782 cases if health insurance gains associated with ACA are lost. Estimated cost savings – balancing increased CRC screening/testing costs against decreased cancer treatment costs – are approximately $30 M and $970 M for Medicaid expansion and Medicare-for-all scenarios, respectively, compared to status quo. Insurance expansion is likely to improve CRC screening both overall and in underserved populations while saving money, with the largest savings realized by Medicare.}, journal={PREVENTIVE MEDICINE}, author={Lich, Kristen Hassmiller and Meghan C. O'Leary and Nambiar, Siddhartha and Townsley, Rachel M. and Mayorga, Maria E. and Hicklin, Karen and Frerichs, Leah and Shafer, Paul R. and Davis, Melinda M. and Wheeler, Stephanie B.}, year={2019}, month={Dec} }
 @article{davis_nambiar_mayorga_sullivan_hicklin_meghan c. o'leary_dillon_lich_gu_lind_et al._2019, title={Mailed FIT (fecal immunochemical test), navigation or patient reminders? Using microsimulation to inform selection of interventions to increase colorectal cancer screening in Medicaid enrollees}, volume={129}, ISSN={["1096-0260"]}, url={http://dx.doi.org/10.1016/j.ypmed.2019.105836}, DOI={10.1016/j.ypmed.2019.105836}, abstractNote={Colorectal cancer (CRC) can be effectively prevented or detected with guideline concordant screening, yet Medicaid enrollees experience disparities. 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. Each intervention scenario raised CRC screening rates compared to usual care, with improvements as high as 11.6 percentage points (Mailed FIT + Navigation) and as low as 2.5 percentage points (Reminders) after one year. Compared to usual care, Mailed FIT + Navigation would raise CRC screening rates 20.2 percentage points after five years - averting nearly 77 cancer cases (a reduction of 113 per 100,000) and exceeding national screening targets. 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. To approach national CRC screening targets, health system stakeholders are encouraged to implement Mailed FIT with or without Navigation and Reminders.}, journal={PREVENTIVE MEDICINE}, author={Davis, Melinda M. and Nambiar, Siddhartha and Mayorga, Maria E. and Sullivan, Eliana and Hicklin, Karen and Meghan C. O'Leary and Dillon, Kristen and Lich, Kristen Hassmiller and Gu, Yifan and Lind, Bonnie K. and et al.}, year={2019}, month={Dec} }
 @misc{fishbein_nambiar_mckenzie_mayorga_miller_tran_schubel_agor_kim_capan_2019, title={Objective measures of workload in healthcare: a narrative review}, volume={33}, ISSN={["1758-6542"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85077284434&partnerID=MN8TOARS}, DOI={10.1108/IJHCQA-12-2018-0288}, abstractNote={PurposeWorkload 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.}, number={1}, journal={INTERNATIONAL JOURNAL OF HEALTH CARE QUALITY ASSURANCE}, author={Fishbein, Daniela and Nambiar, Siddhartha and McKenzie, Kendall and Mayorga, Maria and Miller, Kristen and Tran, Kevin and Schubel, Laura and Agor, Joseph and Kim, Tracy and Capan, Muge}, year={2019}, month={Dec}, pages={1–17} }
 @inproceedings{simulating uncertainty of early warning scores in sepsis detection_2019, url={http://dx.doi.org/10.1145/3307339.3343252}, DOI={10.1145/3307339.3343252}, abstractNote={Sepsis, a syndrome of acute organ dysfunction secondary to a systemic infection, has been recognized as a growing burden on healthcare systems and is responsible for nearly $24 billion annually. Various early sepsis detection scores have been developed to quantify the risk of clinical deterioration. While the scores quantify risk, they often overlook the uncertainties associated with the scores, defined as a feature of a scoring system caused by any absence of a component in documented Electronic Health Records (EHR). Using a discrete-event simulation approach, we analyzed the simulated 1) composition of a selected early warning score, 2) timing of worst and best score values of sepsis population in the Emergency Department, and 3) changes over time in uncertainty throughout the hospitalization. Composition referred to simulated availability of score components and uncertainty was represented by the percent of components that are unavailable at a given time point. Data was collected from 15,982 patients with 22,968 visits meeting infection and sepsis criteria within subpopulations with different levels of severity of sepsis. Simulated trajectories indicated differences among the sub-populations. The first complete score and worst score values were found to be higher for those who died with sepsis compared to those that survived with infection and/or with sepsis. The findings from this study provide a framework to capture the stochastic nature of early warning scores and can inform implementation of scores in clinical practice with the goal of supporting early detection of sepsis.}, booktitle={Proceedings of the 10th ACM International Conference on Bioinformatics, Computational Biology and Health Informatics  - BCB '19}, year={2019} }
 @inproceedings{nambiar_mayorga_o’leary_lich_wheeler_2018, title={A simulation model to assess the impact of insurance expansion on colorectal cancer screening at the population level}, booktitle={Proceedings of the 2018 Winter Simulation Conference}, author={Nambiar, Siddhartha and Mayorga, Maria E and O’Leary, Meghan C and Lich, Kristen Hassmiller and Wheeler, Stephanie B}, year={2018}, pages={2701–2712} }
 @article{madathil_nambiar_mason_kurz_2018, title={On scheduling a photolithography area containing cluster tools}, volume={121}, ISSN={["1879-0550"]}, url={http://dx.doi.org/10.1016/j.cie.2018.05.036}, DOI={10.1016/j.cie.2018.05.036}, abstractNote={Photolithography is typically the bottleneck process in semiconductor manufacturing. 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.}, journal={COMPUTERS & INDUSTRIAL ENGINEERING}, author={Madathil, Sreenath Chalil and Nambiar, Siddhartha and Mason, Scott J. and Kurz, Mary E.}, year={2018}, month={Jul}, pages={177–188} }
 @article{nambiar_nikolaev_greene_cavuoto_bisantz_2016, title={Low-Cost Sensor System Design for In-Home Physical Activity Tracking}, volume={4}, url={http://dx.doi.org/10.1109/jtehm.2016.2620971}, DOI={10.1109/jtehm.2016.2620971}, abstractNote={An aging and more sedentary population requires interventions aimed at monitoring physical activity, particularly within the home. 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.}, journal={IEEE Journal of Translational Engineering in Health and Medicine}, author={Nambiar, S. and Nikolaev, A. and Greene, M. and Cavuoto, L. and Bisantz, A.}, year={2016} }
 @article{stearns_nambiar_nikolaev_semenov_mcintos_2014, title={Towards evaluating and enhancing the reach of online health forums for smoking cessation}, volume={3}, url={http://dx.doi.org/10.1007/s13721-014-0069-7}, DOI={10.1007/s13721-014-0069-7}, abstractNote={Online pro-health social networks facilitating smoking cessation through web-assisted interventions have flourished in the past decade. In order to properly evaluate and increase the impact of this form of treatment on society, one needs to understand and be able to quantify its reach, as defined within the widely-adopted RE-AIM framework. In the online communication context, user engagement is an integral component of reach. 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 ten 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. To this end, the challenges and opportunities are identified in the development of thread recommendation systems using core-users as a strategic resource for effective and efficient spread of healthy behaviors, in particular smoking cessation.}, number={1}, journal={Network Modeling Analysis in Health Informatics and Bioinformatics}, author={Stearns, M. and Nambiar, S. and Nikolaev, A. and Semenov, A. and McIntos, S.}, year={2014}, month={Dec} }
 @inproceedings{nambiar_madathil_paul_zelaya_koikkara_gramopadhye_2013, title={Understanding the visualization strategies used by experts when reading mechanical part drawings using eye tracking}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900300219&partnerID=MN8TOARS}, booktitle={IIE Annual Conference and Expo 2013}, author={Nambiar, S. and Madathil, K.C. and Paul, M.D. and Zelaya, M. and Koikkara, R. and Gramopadhye, A.K.}, year={2013}, pages={503–511} }
 @inproceedings{subash_nambiar_kumar_2012, title={BrailleKey: An alternative Braille text input system: Comparative study of an innovative simplified text input system for the visually impaired}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875701592&partnerID=MN8TOARS}, DOI={10.1109/IHCI.2012.6481790}, abstractNote={This paper explores the efficacy of using an alternate text input system for the blind, based entirely on Braille alphabets for touch-screen mobile devices. A comparative study was performed wherein a prototype application developed by the authors was compared against the Voice-Over technology developed for iOS (Apple's mobile operating system. The study conducted on five blind subjects show that this system can be used as a viable alternative to the existing input methods that have been developed for this purpose.}, booktitle={4th International Conference on Intelligent Human Computer Interaction: Advancing Technology for Humanity, IHCI 2012}, author={Subash, N.S. and Nambiar, S. and Kumar, V.}, year={2012} }