Modeling the impact of integrating HIV and outpatient health services on patient waiting times in an urban health clinic in Zambia

Background

Rapid scale up of HIV treatment programs in sub-Saharan Africa has refueled the long-standing health policy debate regarding the merits and drawbacks of vertical and integrated system. Recent pilots of integrating outpatient and HIV services have shown an improvement in some patient outcomes but deterioration in waiting times, which can lead to worse health outcomes in the long run.

Methods

A pilot intervention involving integration of outpatient and HIV services in an urban primary care facility in Lusaka, Zambia was studied. Data on waiting time of patients during two seven-day periods before and six months after the integration were collected using a time and motion study. Statistical tests were conducted to investigate whether the two observation periods differed in operational details such as staffing, patient arrival rates, mix of patients etc. A discrete event simulation model was constructed to facilitate a fair comparison of waiting times before and after integration. The simulation model was also used to develop alternative configurations of integration and to estimate the resulting waiting times.

Results

Comparison of raw data showed that waiting times increased by 32% and 36% after integration for OPD and ART patients respectively (p<0.01). Using simulation modeling, we found that a large portion of this increase could be explained by changes in operational conditions before and after integration such as reduced staff availability (p<0.01) and longer breaks between consecutive patients (p<0.05). Controlling for these differences, integration of services, per se, would have resulted in a significant decrease in waiting times for OPD and a moderate decrease for HIV services.

Conclusions

Integrating health services has the potential of reducing waiting times due to more efficient use of resources. However, one needs to ensure that other operational factors such as staff availability are not adversely affected due to integration.     

某院门诊排队信息的建模分析和整改对策

运用排队论原理,对某院门诊窗口排队信息进行建模调查分析,通过采取系列整改对策,提高了工作效率,减少了病员排队和等候。     

Vehicle dispatching for highly loaded semiconductor production considering bottleneck machines first

Semiconductor wafer fabrication lines can be characterized by re-entrant product flow, long production lead-time, large variety of production processes, and large capital investment. These distinctive characteristics make the flow control in the fab very complicated. Throughput rate and lead-time are among the most important performance measures. The throughput rate is usually determined by a bottleneck resource, and the lead-time depends on the machine utilization level and the amount of variability in the system. Due to the high efficiency of material handling and reduced particles, automated material handling systems such as automatic guided vehicles (AGVs), overhead hoist transporters (OHTs), and overhead shuttles (OHSs) are being widely used in wafer fabrication lines (wafer fabs) instead of human operators. Although a material handling system itself is seldom a bottleneck of production in a fab, it is important for that to effectively support the bottleneck machines to maximize the throughput and reduce production lead-time. This paper presents a vehicle dispatching procedure based on the concept of theory of constraints, in which vehicle dispatching decisions are made to utilize the bottleneck machines at the maximum level. Simulation experiments have been performed to compare the proposed vehicle dispatching procedure with existing ones under different levels of machine utilization, vehicle utilization, and local buffer capacity.     

Decreasing waiting time for treatment before and during implementation of cancer patient pathways in Norway

Background: In 2015, Norway implemented cancer patient pathways to reduce waiting times for treatment. The aims of this paper were to describe patterns in waiting time and their association with patient characteristics for colorectal, lung, breast and prostate cancers.Methods: National, population-based data from 2007 to 2016 were used. A multivariable quantile regression examined the association between treatment period, age, stage, sex, place of residence, and median waiting times.Results: Reduction in median waiting times for radiotherapy among colorectal, lung and prostate cancer patients ranged from 14 to 50 days. Median waiting time for surgery remained approximately 21 days for both colorectal and breast cancers, while it decreased by 7 and 36 days for lung and prostate cancers, respectively. The proportion of lung and prostate cancer patients with metastatic disease at the time of diagnosis decreased, while the proportion of colorectal patients with localised disease and patients with stage I breast cancer increased (p < 0.001). After adjusting for case-mix, a patient’s place of residence was significantly associated with waiting time for treatment (p < 0.001), however, differences in waiting time to treatment decreased over the study period.Conclusions: Between 2007 and 2016, Norway experienced improved stage distributions and consistently decreasing waiting times for treatment. While these improvements occurred gradually, no significant change was observed from the time of cancer patient pathway implementation.     

Traffic load monitoring and load balancing for the Internet

This paper proposes a class-based multipath routing algorithm to support Quality of Service (QoS). The algorithm is called Two-level Class-based Routing with Prediction (TCRP). Since frequently flooding routing information is very expensive for dynamic routing, the TCRP is designed to have the traffic load information monitored in one stable period as a guide to control traffic forwarding in the next stable period. The monitoring function is implemented by adopting the leaky bucket mechanism. In TCRP, the path selection function can utilize resources on multipath to achieve load balancing, increase network throughput and reduce the queuing delay. The extensive simulation is conducted to analyze the performance of the TCRP algorithm. The simulation results show that the TCRP can reduce packet drops and increase network throughput in any size network topology. This revised version was published online in July 2006 with corrections to the Cover Date.     

Simultaneous determination of lot size and production rate at capacity-constrained multiple-product systems

In the capacity constrained manufacturing systems where multiple product types are manufactured, the products are often produced in lots. Although the lot production may increase the system throughput by reducing changeover times, it may also increase production lead time because each item in a large lot has a long waiting time. Hence, a production manager should consider both throughput and lead time at the same time when deciding production lot sizes. This paper, which is an extension to the previous work done in Koo et al. (2007) that assumes homogeneous setup times, addresses a lot sizing problem in the system with multiple product types and unequal setup times. We develop a non-linear optimization model for simultaneous determination of throughput rate and lot size for each product. Since this optimization model cannot be solved analytically, we propose a heuristic solution procedure by analyzing the characteristics of the problem. Some numerical examples are presented to validate the proposed model, and finally the performance of the heuristic procedure is evaluated by comparison with the results of simulation experiments.     

Theory and applications of a computationally efficient cohort simulation model of human reproduction

Ease of implementation and computational efficiency are two necessary criteria if a simulation system is to be run repeatedly. Described in this paper is a cohort simulation model, based on the theory of terminating renewal processes, which satisfies these two criteria. There are two versions of the model. In one version, waiting times till pregnancy and times spent in the postpartum sterile state, as well as parity progression ratios reflecting hypothetical birth intentions, are taken into account. Unlike simulation systems described in earlier papers, pregnancy wastage is not accommodated in this version of the model. A second version is a model of birth intervals in which parity progression ratios and distributions of waiting times among live births, both of which may reflect pregnancy wastage when based on birth history data, serve as computer input. Female mortality, expressed as a survival function, and a distribution of age at marriage in a cohort are essential parts of both versions of the system. High efficiency in computing the many required convolutions has been obtained by use of a fast Fourier transform algorithm. After an overview of computer software design is given, the computer input for twelve simulation runs is described. These twelve runs are designed to test the impact of various combinations of levels of mortality, age of marriage, and fertility on population growth. One of the interesting substantive conclusions stemming from the simulation runs was that in populations of low mortality and fertility, late age at marriage, as observed in some historical populations, can be a significant factor in increasing the population doubling time.     

Strengthening Health Systems at Facility-Level: Feasibility of Integrating Antiretroviral Therapy into Primary Health Care Services in Lusaka,Zambia

Introduction

HIV care and treatment services are primarily delivered in vertical antiretroviral (ART) clinics in sub-Saharan Africa but there have been concerns over the impact on existing primary health care services. This paper presents results from a feasibility study of a fully integrated model of HIV and non-HIV outpatient services in two urban Lusaka clinics.

Methods

Integration involved three key modifications: i) amalgamation of space and patient flow; ii) standardization of medical records and iii) introduction of routine provider initiated testing and counseling (PITC). Assessment of feasibility included monitoring rates of HIV case-finding and referral to care, measuring median waiting and consultation times and assessing adherence to clinical care protocols for HIV and non-HIV outpatients. Qualitative data on patient/provider perceptions was also collected.

Findings

Provider and patient interviews at both sites indicated broad acceptability of the model and highlighted a perceived reduction in stigma associated with integrated HIV services. Over six months in Clinic 1, PITC was provided to 2760 patients; 1485 (53%) accepted testing, 192 (13%) were HIV positive and 80 (42%) enrolled. Median OPD patient-provider contact time increased 55% (6.9 vs. 10.7 minutes; p<0.001) and decreased 1% for ART patients (27.9 vs. 27.7 minutes; p = 0.94). Median waiting times increased by 36 (p<0.001) and 23 minutes (p<0.001) for ART and OPD patients respectively. In Clinic 2, PITC was offered to 1510 patients, with 882 (58%) accepting testing, 208 (24%) HIV positive and 121 (58%) enrolled. Median OPD patient-provider contact time increased 110% (6.1 vs. 12.8 minutes; p<0.001) and decreased for ART patients by 23% (23 vs. 17.7 minutes; p<0.001). Median waiting times increased by 47 (p<0.001) and 34 minutes (p<0.001) for ART and OPD patients, respectively.

Conclusions

Integrating vertical ART and OPD services is feasible in the low-resource and high HIV-prevalence setting of Lusaka, Zambia. Integration enabled shared use of space and staffing that resulted in increased HIV case finding, a reduction in stigma associated with vertical ART services but resulted in an overall increase in patient waiting times. Further research is urgently required to assess long-term clinical outcomes and cost effectiveness in order to evaluate scalability and generalizability.     

Towards operational cost minimization for cloud bursting with deadline constraints in hybrid clouds

In hybrid clouds, there is a technique named cloud bursting which can allow companies to expand their capacity to meet the demands of peak workloads in a low-priced manner. In this work, a cost-aware job scheduling approach based on queueing theory in hybrid clouds is proposed. The job scheduling problem in the private cloud is modeled as a queueing model. A genetic algorithm is applied to achieve optimal queues for jobs to improve the utilization rate of the private cloud. Then, the task execution time is predicted by back propagation neural network. The max–min strategy is applied to schedule tasks according to the prediction results in hybrid clouds. Experiments show that our cost-aware job scheduling algorithm can reduce the average job waiting time and average job response time in the private cloud. In additional, our proposed job scheduling algorithm can improve the system throughput of the private cloud. It also can reduce the average task waiting time, average task response time and total costs in hybrid clouds.     

Colored extrinsic fluctuations and stochastic gene expression

Stochasticity is both exploited and controlled by cells. Although the intrinsic stochasticity inherent in biochemistry is relatively well understood, cellular variation, or ‘noise’, is predominantly generated by interactions of the system of interest with other stochastic systems in the cell or its environment. Such extrinsic fluctuations are nonspecific, affecting many system components, and have a substantial lifetime, comparable to the cell cycle (they are ‘colored’). Here, we extend the standard stochastic simulation algorithm to include extrinsic fluctuations. We show that these fluctuations affect mean protein numbers and intrinsic noise, can speed up typical network response times, and can explain trends in high‐throughput measurements of variation. If extrinsic fluctuations in two components of the network are correlated, they may combine constructively (amplifying each other) or destructively (attenuating each other). Consequently, we predict that incoherent feedforward loops attenuate stochasticity, while coherent feedforwards amplify it. Our results demonstrate that both the timescales of extrinsic fluctuations and their nonspecificity substantially affect the function and performance of biochemical networks.     

Computer Simulation Model of an X-ray Department

A computer simulation model has been designed to predict the effects of changes in the work load and resources of an x-ray department. The model has been used to produce histograms of patient waiting times and to show the effect on these of introducing changes in the speed of processing films and in the numbers of cubicles and radiographers available. The predicted benefit of using a faster film processor has been confirmed in practice.     

排队论模型在军队医院门诊超声科设备配置中的应用

目的 探讨排队论模型在军队医院门诊超声科设备配置中的应用效果。方法 运用现场调查法和排队论模型,计算超声科设备工作强度（r）,患者排队等待人数（Lq）,窗口逗留人数（Ls）,平均排队等待时间（Wq）,平均逗留时间（Ws）,设备空闲概率（P0）患者到达必须等待的概率（P）等运行指标,并对应用排队论模型配置设备前后患者及技师进行满意度调查。结果 超声科上下午分别配置6台和3台设备较为合理,在应用排队论模型配置设备后,技师和患者的满意度均得到明显提高（P＜0.05）。结论 利用排队论的方法可以较好地配置超声科设备,为提高服务效率提供科学参考。     

Incidence of hospitalization in patients receiving short course palliative cranial radiotherapy on outpatient basis in a limited resource setting – Experience from a regional cancer center in India

AimTo investigate incidence of toxicity and related hospitalization among patients treated at our institute by a short course of palliative cranial radiotherapy against a longer, widely established schedule.BackgroundShorter schedule palliative cranial radiotherapy is more convenient for patients and reduce waiting times. Although many studies have established safety of short schedules, the need for hospitalization due to acute treatment toxicity remains under-explored. Hospital admissions are an economic burden both for the patient and healthcare system in a limited resource setting. Delivery of treatment on an outpatient basis and within shorter times is preferred by patients, caregivers and healthcare staff.Materials and methodsThis was a prospective study on 68 patients treated with palliative whole brain radiotherapy between November 2010 and October 2012. One group received 20 Gy in 5 fractions over 1 week and the other group, 30 Gy in 10 fractions over 2 weeks. Treatment toxicity due to cranial radiotherapy was assessed as per RTOG acute and late toxicity criteria. Need for hospitalization owing to acute toxicity was also noted. Significant differences in the study parameters between the two groups were calculated by Fisher's t-test.ResultsRequirement for hospital stay due to acute toxicity was not significantly different between the two groups. Patients in both groups experienced similar toxicity both during and after treatment.ConclusionsThe shorter course entailed no significant increase in toxicity related admissions, suitable for limited resource settings where patient transport is difficult, there are financial constraints, and the healthcare system is overburdened.     

非小细胞肺癌低分割放疗研究进展

肺癌是全球发病率和死亡率第一的恶性肿瘤,虽然放疗在NSCLC的治疗中具有可观的局部疗效,但临床上仍有部分患者出现治疗失败。放疗失败的主要原因是局部未控、复发或远处转移。与常规分割相比,大分割放疗可在不增加放疗次数的情况下提高总的放疗剂量;对于接受相同BED照射的NSCLC患者,大分割放疗除了能带来局部控制率上的增加外,还可减少治疗次数,节省治疗时间和费用,增加病人的便捷,提高医用加速器的使用效率。L-Q模型的数据在预测大分割放疗疗效时存在许多局限。除经典L-Q模型所模拟的机制外,还可能有其他机制的参与。分子影像是无创性评价放疗疗效的可靠手段,利用不同分子显像剂结合胞内特定靶分子,能够对恶性肿瘤的代谢水平、乏氧状态、增殖能力等情况进行较为准确的评估,为大分割放疗提供良好的疗效评估手段并成为研究其特殊放射生物效应的有力工具。     

Modeling the effect of imperfect staggering in product inflow using queuing theory: revisiting block stacking layout

Conventional approaches to layout design of block stacked warehouses assume perfect staggering of product inflow leading to perfect sharing of space among products. Since such an assumption is seldom true, we argue that warehouses designed using the conventional approach may result in choking situations with large quantities of inventory waiting outside the storage areas. On the other hand, liberal space allocation such as in dedicated policy might lead to under-utilization of space. In this paper, we take a fresh look at the block stacked layout problem, modeling the effect of imperfectly staggered product arrivals using queuing theory. Analytical expressions are derived for arrival time and processing time coefficients of variation using warehouse parameters and design variables. Further, we develop a bi-objective optimization model to minimize both the space cost and waiting time. Our approach provides design options over a total space cost-waiting time trade-off frontier as opposed to singular design points given by conventional approaches. Computational experiments are conducted to derive further insights into the design of block stacked warehouses.

     

A Discrete Event Simulation Model for Evaluating the Performances of an M/G/C/C State Dependent Queuing System

M/G/C/C state dependent queuing networks consider service rates as a function of the number of residing entities (e.g., pedestrians, vehicles, and products). However, modeling such dynamic rates is not supported in modern Discrete Simulation System (DES) software. We designed an approach to cater this limitation and used it to construct the M/G/C/C state-dependent queuing model in Arena software. Using the model, we have evaluated and analyzed the impacts of various arrival rates to the throughput, the blocking probability, the expected service time and the expected number of entities in a complex network topology. Results indicated that there is a range of arrival rates for each network where the simulation results fluctuate drastically across replications and this causes the simulation results and analytical results exhibit discrepancies. Detail results that show how tally the simulation results and the analytical results in both abstract and graphical forms and some scientific justifications for these have been documented and discussed.     

Waiting for coronary revascularization in Toronto: 2 years' experience with a regional referral office.

OBJECTIVES: To determine the frequency of major adverse events among patients awaiting coronary revascularization; to assess the match between referring physicians'' estimates of urgency, a computer-generated multifactorial urgency rating score and actual waiting times; to determine the changes in waiting times as capacity for bypass surgery increased; and to evaluate the influence of choice of procedure or operator on waiting times. DESIGN: Consecutive case series. SETTING: Greater Toronto region. SUBJECTS: All 571 patients referred to an organized referral office by cardiologists at hospitals without on-site revascularization facilities between Jan. 3, 1989, and June 30, 1991. MAIN OUTCOME MEASURES: Preoperative fatal or nonfatal myocardial infarction; proportions of patients waiting longer than the maximum period recommended for their urgency rating; mean waiting times for various subgroups; and correlations among referring physicians'' urgency ratings, computer-generated multifactorial urgency scores and waiting times. RESULTS: Of the 496 patients accepted for a procedure 5 had fatal cardiac events and 3 nonfatal myocardial infarction. Events occurred three times more often in patients with left mainstem disease than in those in other anatomic categories (relative risk [RR] 3.05, 95% confidence interval [CI] 1.48 to 6.27, p = 0.03). Both the computer-generated scores and the referring physicians'' scores were correlated with the actual waiting time (r = 0.46 and 0.57 respectively). Waiting times and the proportion of patients with excessive waiting times fell during the study period (p < 0.0001). However, urgent cases were much less likely to be done "on time" than those with a recommended waiting time of more than 2 weeks (RR 0.16, 95% CI 0.11 to 0.25, p < 0.0001). The mean wait for coronary artery bypass grafting (CABG) was 22.73 days if the referral office was allowed to find a surgeon or interventional cardiologist and 35.31 days if one was requested (p = 0.002 after adjustment for urgency scores). CONCLUSIONS: Death of a patient on the waiting list is uncommon in an organized referral system. Patients with left main-stem disease are at higher risk of death than those in other anatomic categories. There were significant correlations between referring physicians'' ratings of urgency, multifactorial urgency scores and actual waiting times. Expansion of capacity for CABG led to shorter waiting times, but patients with unstable symptoms continued to wait longer than recommended. Requests for a specific surgeon caused significantly longer delays.     

The More the Tubular: Dynamic Bundling of Actin Filaments for Membrane Tube Formation

Tubular protrusions are a common feature of living cells, arising from polymerization of stiff protein filaments against a comparably soft membrane. Although this process involves many accessory proteins in cells, in vitro experiments indicate that similar tube-like structures can emerge without them, through spontaneous bundling of filaments mediated by the membrane. Using theory and simulation of physical models, we have elaborated how nonequilibrium fluctuations in growth kinetics and membrane shape can yield such protrusions. Enabled by a new grand canonical Monte Carlo method for membrane simulation, our work reveals a cascade of dynamical transitions from individually polymerizing filaments to highly cooperatively growing bundles as a dynamical bottleneck to tube formation. Filament network organization as well as adhesion points to the membrane, which bias filament bending and constrain membrane height fluctuations, screen the effective attractive interactions between filaments, significantly delaying bundling and tube formation.     

A policy management game for mass casualty incidents: an experimental study

The number of complex and unique mass casualty incidents has increased due to natural and technological disasters as well as man-made disasters such as political instabilities, economic recession, and terrorism. Thus, health care policy-makers such as the Austrian Samaritan Organization have been continuously improving the training of emergency staff to enable them to quickly evacuate an emergency site, to minimize the number of fatalities at the incident site, and to decrease the patients’ waiting time for treatment. We developed a policy management game to provide a training tool for emergency staff to support such policy-makers. In addition, with this game students can be educated on scheduling and planning techniques such as simulation, queuing theory, and resource allocation. To investigate the potential of our policy management game, we conducted an experimental study with 96 participants including students, practitioners from health care services, and researchers. They acted as incident commanders to decide on sending medical staff to triage, to different treatment rooms for care and to on-site transportation, as well as to transportation to hospitals during three game runs. The participants rated the general structure and organization of the experiment as high. The performance was also improved by many participants during the experiment. We found differences in performance among the different participant groups.