Modeling complex treatment strategies: construction and validation of a discrete event simulation model for glaucoma

Cost-effectiveness of monitoring ocular hypertension based on a risk prediction tool

BACKGROUND/AIMS

To assess the cost-effectiveness of making treatment decisions for patients with ocular hypertension (OHT) based on a risk prediction (RP) tool in the United Kingdom.

METHODS

A discrete event simulation model was constructed to compare the cost-effectiveness of an alternative care pathway in which the treatment decision was guided by a validated RP tool in secondary care against decision-making based on the standard care (SC). Individual patient sampling was used. Patients diagnosed with OHT and with an intraocular pressure of 24 mm Hg or over entered the model with a set of predefined individual characteristics related to their risk of conversion to glaucoma. These characteristics were retrieved from electronic medical records (n=5740). Different stages of glaucoma were modelled following conversion to glaucoma.

RESULTS

Almost all (99%) patients were treated using the RP strategy, and less than half (47%) of the patients were treated using the SC strategy. The RP strategy produced higher cost but also higher quality-adjusted life years (QALYs) than the SC strategy. The RP strategy was cost-effective compared with the SC strategy in the base-case analysis, with an incremental cost-effectiveness ratio value of £11 522. The RP strategy had a 96% probability of being cost-effective under a £20 000 per QALY threshold.

CONCLUSIONS

The use of an RP tool for the management of patients with OHT is likely to be cost-effective. However, the generalisability of the result might be limited due to the high-risk nature of this cohort and the specific RP threshold used in the study.

Feasibility of in-home monitoring for people with glaucoma: the I-TRAC mixed-methods study

Background

Glaucoma is a chronic disease of the optic nerve and a leading cause of severe visual loss in the UK. Once patients have been diagnosed, they need regular monitoring at hospital eye services. Recent advances in technology mean patients with glaucoma can now monitor their disease at home. This could be more convenient for patients and potentially reduce costs and increase capacity for the NHS. However, it is uncertain whether self-monitoring would be acceptable or possible for patients with glaucoma.

Objectives

The objectives were to: identify which patients are most appropriate for home monitoring; understand views of key stakeholders (patients, clinicians, researchers) on whether home glaucoma monitoring is feasible and acceptable; develop a conceptual framework for the economic evaluation of home glaucoma monitoring; and explore the need for and provide evidence on the design of a future study to evaluate the clinical and cost-effectiveness of digital technologies for home monitoring of glaucoma.

Design

In-home Tracking of glaucoma: Reliability, Acceptability, and Cost (I-TRAC) was a multiphase mixed-methods feasibility study with key components informed by theoretical and conceptual frameworks.

Setting

Expert glaucoma specialists in the UK recruited through professional glaucoma societies; study site staff and patient participants recruited through three UK hospital eye services (England, Scotland, Northern Ireland); and UK research teams recruited though existing networks.

Intervention

Home tonometer that measures intraocular pressure and a tablet computer with a visual function application. Patients were asked to use the technology weekly for 12 weeks.

Results

Forty-two patients were recruited. Retention and completion of follow-up procedures was successful, with 95% (n = 40) completing the 3-month follow-up clinic visits. Adherence to the interventions was generally high [adherence to both devices (i.e. ≥ 80% adherence) was 55%]. Overall, patients and healthcare professionals were cautiously optimistic about the acceptability of digital technologies for home monitoring of patients with glaucoma. While most clinicians were supportive of the potential advantages glaucoma home monitoring could offer, concerns about the technologies (e.g. reliability and potential to miss disease progression) and how they would fit into routine care need to be addressed. Additionally, clarity is required on defining the ideal population for this intervention. Plans for how to evaluate value for money in a future study were also identified. However, the study also highlighted several unknowns relating to core components of a future evaluative study that require addressing before progression to a definitive effectiveness trial.

Limitations

The main limitation relates to our sample and its generalisability, for example, the over-representation of educated persons of white ethnicity who were generally experienced with technology and research motivated.

Conclusions

The In-home Tracking of glaucoma: Reliability, Acceptability, and Cost study has demonstrated 'cautious optimism' when considering patients' and healthcare professionals' views on the acceptability of digital technologies for home monitoring of patients with glaucoma. However, the study also highlighted several unknowns relating to the research question and design of a future evaluative study that require addressing before progression to a randomised controlled trial.

Future work

Further research is required to determine the appropriate population (i.e. low vs. high risk of progression) and further refine the intervention components and delivery for planning of future evaluation studies.

Study registration

This study is registered as Research Registry #6213.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR129248) and is published in full in Health Technology Assessment; Vol. 28, No. 44. See the NIHR Funding and Awards website for further award information.

A Cost Analysis with the Discrete-Event Simulation Application in Nurse and Doctor Employment Management

AIM

This study aimed to analyze the treatment cost of a patient, depending on the number of patients treated, patient waiting times, and the number of nurses and doctors employed in an emergency department of a private hospital.

BACKGROUND

Within health systems, changes in healthcare resources can be very costly, especially if these changes are long-term. The discrete-event simulation method described in this paper allows for the monitoring and analysis of complicated changes in real systems by using computer-based modeling.

METHOD

The discrete event simulation model was derived from 9 scenarios according to the number of nurses and doctors, and a comparison was made between the results of the scenarios and the actual results.

RESULTS

Among the scenarios, scenario 6 provided the lowest treatment cost for a patient by employing three doctors and two nurses with the best performance. The cost of treatment for a patient varies betweenŧ 9.00-ŧ 11.00 depending on the value of δ, and the daily cost of these resources to the hospital is ŧ1300.77.

CONCLUSIONS

This study provides a clear picture of a cost analysis comparison based on changes made about the actual health system in the computer-based simulated environment. Implications for Nursing Management The workforce data of nurses and doctors offers enough detail for cost analysis in healthcare settings to calculate the cost of treatment for a patient.

Evaluating Montréal's harm reduction interventions for people who inject drugs: protocol for observational study and cost-effectiveness analysis

INTRODUCTION

The main harm reduction interventions for people who inject drugs (PWID) are supervised injection facilities, needle and syringe programmes and opioid agonist treatment. Current evidence supporting their implementation and operation underestimates their usefulness by excluding skin, soft tissue and vascular infections (SSTVIs) and anoxic/toxicity-related brain injury from cost-effectiveness analyses (CEA). Our goal is to conduct a comprehensive CEA of harm reduction interventions in a setting with a large, dispersed, heterogeneous population of PWID, and include prevention of SSTVIs and anoxic/toxicity-related brain injury as measures of benefit in addition to HIV, hepatitis C and overdose morbidity and mortalities averted.

METHODS AND ANALYSIS

This protocol describes how we will develop an open, retrospective cohort of adult PWID living in Québec between 1 January 2009 and 31 December 2020 using administrative health record data. By complementing this data with non-linkable paramedic dispatch records, regional monthly needle and syringe dispensation counts and repeated cross-sectional biobehavioural surveys, we will estimate the hazards of occurrence and the impact of Montréal's harm reduction interventions on the incidence of drug-use-related injuries, infections and deaths. We will synthesise results from our empirical analyses with published evidence to simulate infections and injuries in a hypothetical population of PWID in Montréal under different intervention scenarios including current levels of use and scale-up, and assess the cost-effectiveness of each intervention from the public healthcare payer's perspective.

ETHICS AND DISSEMINATION

This study was approved by McGill University's Institutional Review Board (Study Number: A08-E53-19B). We will work with community partners to disseminate results to the public and scientific community via scientific conferences, a publicly accessible report, op-ed articles and open access peer-reviewed journals.

Modeling Early Warning Systems: Construction and Validation of a Discrete Event Simulation Model for Heart Failure

OBJECTIVES

Developing and validating a discrete event simulation model that is able to model patients with heart failure managed with usual care or an early warning system (with or without a diagnostic algorithm) and to account for the impact of individual patient characteristics in their health outcomes.

METHODS

The model was developed using patient-level data from the Trans-European Network - Home-Care Management System study. It was coded using RStudio Version 1.3.1093 (version 3.6.2.) and validated along the lines of the Assessment of the Validation Status of Health-Economic decision models tool. The model includes 20 patient and disease characteristics and generates 8 different outcomes. Model outcomes were generated for the base-case analysis and used in the model validation.

RESULTS

Patients managed with the early warning system, compared with usual care, experienced an average increase of 2.99 outpatient visits and a decrease of 0.02 hospitalizations per year, with a gain of 0.81 life years (0.45 quality-adjusted life years) and increased average total costs of €11 249. Adding a diagnostic algorithm to the early warning system resulted in a 0.92 life year gain (0.57 quality-adjusted life years) and increased average costs of €9680. These patients experienced a decrease of 0.02 outpatient visits and 0.65 hospitalizations per year, while they avoided being hospitalized 0.93 times. The model showed robustness and validity of generated outcomes when comparing them with other models addressing the same problem and with external data.

CONCLUSIONS

This study developed and validated a unique patient-level simulation model that can be used for simulating a wide range of outcomes for different patient subgroups and treatment scenarios. It provides useful information for guiding research and for developing new treatment options by showing the hypothetical impact of these interventions on a large number of important heart failure outcomes.

Genetic pre-screening for glaucoma in population-based epidemiology: protocol for a double-blind prospective screening study within Lifelines (EyeLife)

Background

Early detection of glaucoma is paramount to maintain patients’ eyesight, however glaucomatous vision loss tends to begin in the periphery with up to 50% of patients unaware they are affected. Because glaucomatous vision loss is permanent, screening appears attractive, but currently is not cost-effective. Therefore we aim to investigate the utility of genetic pre-screening for glaucoma in a population-based setting, called EyeLife.

Methods

EyeLife adopts a double blind prospective design with contrasting groups. Selected participants (n = 1600) from the Lifelines cohort are 55 years of age or older, and of either the highest or lowest 20% of the genetic risk distribution for glaucoma. We obtained a highly curated list of genetic variants from the literature to obtain each participants’ genetic risk for glaucoma. Participants will undergo comprehensive ophthalmic screening. The primary outcome is the relative risk of glaucoma given a high genetic risk compared to a low genetic risk.

Discussion

If genetic pre-screening is successful, it will increase the yield of a glaucoma screening program by focusing on high-risk individuals. This, in turn, may improve long-term visual health of middle-aged and elderly people.

Trial registration

Ethics approval was obtained on January 31, 2019, and the study was retrospectively registered with the Netherlands Trial Register (NL8718) on the 17th of June, 2020.

Assessment of technical errors and validation processes in economic models submitted by the company for NICE technology appraisals

BACKGROUND

Economic models play a central role in the decision-making process of the National Institute for Health and Care Excellence (NICE). Inadequate validation methods allow for errors to be included in economic models. These errors may alter the final recommendations and have a significant impact on outcomes for stakeholders.

OBJECTIVE

To describe the patterns of technical errors found in NICE submissions and to provide an insight into the validation exercises carried out by the companies prior to submission.

METHODS

All forty-one single technology appraisals (STAs) completed in 2017 by NICE were reviewed and all were on medicines. The frequency of errors and information on their type, magnitude, and impact was extracted from publicly available NICE documentation along with the details of model validation methods used.

RESULTS

Two STAs (5 percent) had no reported errors, nineteen (46 percent) had between one and four errors, sixteen (39 percent) had between five and nine errors, and four (10 percent) had more than ten errors. The most common errors were transcription errors (29 percent), logic errors (29 percent), and computational errors (25 percent). All STAs went through at least one type of validation. Moreover, errors that were notable enough were reported in the final appraisal document (FAD) in eight (20 percent) of the STAs assessed but each of these eight STAs received positive recommendations.

CONCLUSIONS

Technical errors are common in the economic models submitted to NICE. Some errors were considered important enough to be reported in the FAD. Improvements are needed in the model development process to ensure technical errors are kept to a minimum.

Intraocular and intracranial pressure in glaucoma patients taking acetazolamide

The alternative mechanical theory of glaucoma, in which an increased pressure difference across the lamina cribrosa (difference between intraocular and intracranial pressure; IOP and ICP), rather than solely an elevated IOP, leads to structural and functional vision loss, is still controversial. If the theory is true, a drug that simultaneously lowers both the IOP and ICP may be ineffective. The aim of this study was to determine how acetazolamide (AAZ; a drug prescribed in glaucoma that aims to lower the IOP) affects both IOP and ICP in glaucoma patients and to compare the magnitude and time course of the induced pressure changes with those of healthy subjects not taking AAZ. IOP and noninvasive ICP (measured through emissions from the ear) were measured in 20 glaucoma patients taking 125 mg of AAZ twice daily. Measurements were taken for 30 minutes before taking the drug and for 2 hours post-ingestion. Comparisons were made with 13 age-similar controls. After 12 hours with no anti-glaucoma medication, AAZ did not further reduce IOP in glaucoma patients compared to controls (P = 0.58) but did reduce ICP compared to controls (P = 0.035), by approximately 4 mmHg. Our findings suggest that there are periods during the day when the pressure difference across the lamina cribrosa is larger in case of AAZ use. Future studies should focus on improving the noninvasive ICP testing, different doses and dosing schedules of AAZ, and the time course of IOP in glaucoma patients not taking AAZ.

TECH-VER: A Verification Checklist to Reduce Errors in Models and Improve Their Credibility

BACKGROUND

In health economic literature, checklists or best practice recommendations on model validation/credibility always declare verification of the programmed model as a fundamental step, such as 'is the model implemented correctly and does the implementation accurately represent the conceptual model?' However, to date, little operational guidance for the model verification process has been given. In this study, we aimed to create an operational checklist for model users or reviewers to verify the technical implementation of health economic decision analytical models and document their verification efforts.

METHODS

Literature on model validation, verification, programming errors and credibility was reviewed systematically from scientific databases. An initial beta version of the checklist was developed based on the checklists/tests identified from the literature and from authors' previous modeling/appraisal experience. Next, the first draft checklist was presented to a number of health economists on several occasions and was tested on different models (built in different software, developed by different stakeholders, including drug manufacturers, consultancies or academia), each time leading to an update of the checklist and culminating in the final version of the TECHnical VERification (TECH-VER) checklist, introduced in this paper.

RESULTS

The TECH-VER necessitates a model reviewer (preferably independent), an executable and transparent model, its input sources, and detailed documentation (e.g. technical report/scientific paper) in which the conceptual model, its implementation, programmed model inputs, and results are reported. The TECH-VER checklist consists of five domains: (1) input calculations; (2) event-state (patient flow) calculations; (3) result calculations; (4) uncertainty analysis calculations; and (5) other overall checks (e.g. validity or interface). The first four domains reflect the verification of the components of a typical health economic model. For these domains, as a prerequisite of verification tests, the reviewer should identify the relevant calculations in the electronic model and assess the provided justifications for the methods used in the identified calculations. For this purpose, we recommend completeness/consistency checks. Afterwards, the verification tests can be conducted for the calculations in each of these stages by checking the correctness of the implementation of these calculations. For this purpose, the following type of tests are recommended in consecutive order: (i) black-box tests, i.e. checking if model calculations are in line with a priori expectations; (ii) white-box testing, i.e. going through the program code details line by line, or cell by cell (recommended for some crucial calculations and if there are some unexpected results from the black-box tests); and (iii) model replication/parallel programming (recommended only in certain situations, and if the issues related to the identified unexpected results from black-box tests could not be resolved through white-box testing). To reduce the time burden of model verification, we suggest a hierarchical order in tests i-iii, where going to the next step is necessary when the previous step fails.

CONCLUSIONS

The TECH-VER checklist is a comprehensive checklist for the technical verification of decision analytical models, aiming to help identify model implementation errors and their root causes while improving the transparency and efficiency of the verification efforts. In addition to external reviews, we consider that the TECH-VER can be used as an internal training and quality control tool for new health economists, while developing their initial models. It is the authors' aim that the TECH-VER checklist transforms itself to an open-source living document, with possible future versions, or 'bolt-on' extensions for specific applications with additional 'fit-for-purpose' tests, as well as 'tips and tricks' and some demonstrative error examples. For this reason, the TECH-VER checklist and the list of black-box tests created in this paper and a few model verification examples is uploaded to an open access, online platform (github and the website of the institute), where other users will also be able to upload their original verification efforts and tests.

Dynamic Monitoring and Control of Irreversible Chronic Diseases with Application to Glaucoma

To manage chronic disease patients effectively, clinicians must know (1) how to monitor each patient (i.e., when to schedule the next visit and which tests to take), and (2) how to control the disease (i.e., what levels of controllable risk factors will sufficiently slow progression). Our research addresses these questions simultaneously and provides the optimal solution to a novel linear quadratic Gaussian state space model. For the objective of minimizing the relative change in state over time (i.e., disease progression), which is necessary for managing irreversible chronic diseases while also considering the cost of tests and treatment, we show that the classical two-way separation of estimation and control holds. This makes a previously intractable problem solvable by decomposition into two separate, tractable problems while maintaining optimality. The resulting optimization is applied to the management of glaucoma. Based on data from two large randomized clinical trials, we validate our model and demonstrate how our decision support tool can provide actionable insights to the clinician caring for a patient with glaucoma. This methodology can be applied to a broad range of irreversible chronic diseases to devise patient-specific monitoring and treatment plans optimally.

Employment of Emergency Advanced Nurses of Turkey: A Discrete-Event Simulation Application

In the present study, problems in emergency services (ESs) were dealt with by analyzing the working system of ESs in Turkey. The purpose of this study was to reduce the waiting times spent in hospitals by employing advanced nurses (ANs) to treat patients who are not urgent, or who may be treated as outpatients in ESs. By applying discrete-event simulation on a 1/24 (daily) and 7/24 (weekly) basis, and by employing ANs, it was determined that the number of patients that were treated increased by 26.71% on a 1/24 basis, and by 15.13% on a 7/24 basis. The waiting time that was spent from the admission to the ES until the treatment time decreased by 38.67% on a 1/24 basis and 53.66% on a 24/7 basis. Similarly, the length of stay was reduced from 82.46 min to 53.97 min in the ES. Among the findings, it was observed that the efficiency rate of the resources was balanced by the employment of ANs, although it was not possible to obtain sufficient efficiency from the resources used in the ESs prior to the present study.

A Generic Model for Follicular Lymphoma: Predicting Cost, Life Expectancy, and Quality-Adjusted-Life-Year Using UK Population-Based Observational Data

OBJECTIVES

To use real-world data to develop a flexible generic decision model to predict cost, life expectancy, and quality-adjusted life-years (QALYs) for follicular lymphoma (FL) in the general patient population.

METHODS

All patients newly diagnosed with FL in the UK's population-based Haematological Malignancy Research Network (www.hmrn.org) between 2004 and 2011 were followed until 2015 (N = 740). Treatment pathways, QALYs, and costs were incorporated into a discrete event simulation to reflect patient heterogeneity, including age and disease management. Two scenario analyses, based on the latest National Institute for Health and Clinical Excellence (NICE) guidelines (rituximab induction therapy for newly diagnosed asymptomatic patients and rituximab maintenance therapy for patients between treatments), were conducted and their economic impacts were compared to current practice.

RESULTS

Incidence-based analysis revealed expected average lifetime costs ranging from £6,165 [US$7,709] to £63,864 [US$79,862] per patient, and average life expectancy from 75 days to 17.56 years. Prevalence-based analysis estimated average annual treatment costs of £60-65 million [US$75-80 million], accounting for approximately 10% of the United Kingdom's annual National Health Service budget for hematological cancers as a whole. Assuming that treatment effects reported in trials are applicable to all patient groups, scenario analyses for two recent NICE guidelines demonstrated potential annual cost savings for the United Kingdom that ranged with uptake frequency from £0.6 million to £11 million [US$0.75-2.75 million].

CONCLUSIONS

Costs, survival, and QALYs associated with FL vary markedly with patient characteristics and disease management. Allowing the production of more realistic outcomes across the patient population as a whole, our model addresses this heterogeneity and is a useful tool with which to evaluate new technologies/treatments to support healthcare decision makers.

Simulation model of the relationship between cesarean section rates and labor duration

Cesarean delivery is the most common major abdominal surgery in many parts of the world, and it accounts for nearly one-third of births in the United States. For a patient who requires a C-section, allowing prolonged labor is not recommended because of the increased risk of infection. However, for a patient who is capable of a successful vaginal delivery, performing an unnecessary C-section can have a substantial adverse impact on the patient's future health. We develop two stochastic simulation models of the delivery process for women in labor; and our objectives are (i) to represent the natural progression of labor and thereby gain insights concerning the duration of labor as it depends on the dilation state for induced, augmented, and spontaneous labors; and (ii) to evaluate the Friedman curve and other labor-progression rules, including their impact on the C-section rate and on the rates of maternal and fetal complications. To use a shifted lognormal distribution for modeling the duration of labor in each dilation state and for each type of labor, we formulate a percentile-matching procedure that requires three estimated quantiles of each distribution as reported in the literature. Based on results generated by both simulation models, we concluded that for singleton births by nulliparous women with no prior complications, labor duration longer than two hours (i.e., the time limit for labor arrest based on the Friedman curve) should be allowed in each dilation state; furthermore, the allowed labor duration should be a function of dilation state.

Systematic Literature Review of Clinical and Economic Outcomes of Micro-Invasive Glaucoma Surgery (MIGS) in Primary Open-Angle Glaucoma

INTRODUCTION

Primary open-angle glaucoma is estimated to affect 3% of the population aged 40-80 years. Trabeculectomy is considered the gold standard in surgical management of glaucoma; however, it is a technically complex procedure that may result in a range of adverse outcomes. Device-augmented, minimally invasive procedures (micro-invasive glaucoma surgeries, MIGS) have been developed aiming for safer and less invasive intraocular pressure (IOP) reduction compared with traditional surgery.

METHODS

This paper presents results from a systematic literature review conducted in accordance with National Institute for Health and Care Excellence requirements for the Medical Technology Evaluation Programme via multiple databases from 2005 to 2016. For clinical outcomes, randomized clinical trials (RCTs) comparing MIGS with trabeculectomy or other therapies, observational studies, and other non-RCTs were included. Clinical outcomes reviewed were the change from baseline in mean IOP levels and change in topical glaucoma medication. Safety was assessed by reported harm and adverse events. For economic evidence, trials on cost-effectiveness, cost-utility, cost-benefit, cost-consequences, cost-minimization, cost of illness, and specific procedure costs were included. Risk of bias was assessed for clinical studies using the Cochrane Risk of Bias tool.

RESULTS

A total of nine RCTs (seven iStents®, one Hydrus®, and one CyPass®), seven non-RCTs (three iStent®, three CyPass®, and one Hydrus®), and 23 economic studies were analyzed. While various forms of trabeculectomy can achieve postoperative IOP of between 11.0 and 13.0 mmHg, MIGS devices described in this review were typically associated with higher postoperative IOP levels. In addition, MIGS devices may result in increased hypotony rates or bleb needling in subconjunctival placed devices, requiring additional medical resources to manage. There is limited available evidence on the cost-effectiveness of MIGS and therefore it remains unclear whether the cost of using MIGS is outweighed by cost savings through decreased medication and need for further interventions.

CONCLUSION

Larger randomized trials and real-world observational studies are needed for MIGS devices to better assess clinical and economic effectiveness. Given the shortage of published data and increasing use of such procedures, living systematic reviews may help to provide ongoing and timely evidence-based direction for clinicians and decision makers. This review highlights the current unmet need for treatments that are easy to implement and reduce long-term IOP levels without increasing postoperative aftercare and cost.

FUNDING

Santen GmbH, Germany.

Early warning systems for the management of chronic heart failure: a systematic literature review of cost-effectiveness models

INTRODUCTION

Describing the general and methodological characteristics of decision-analytical models used in the economic evaluation of early warning systems for the management of chronic heart failure patients and performing a quality assessment of their methodological characteristics is expected to provide concise and useful insight to inform the future development of decision-analytical models in the field of heart failure management.

AREAS COVERED

The literature on decision-analytical models for the economic evaluation of early warning systems for the management of chronic heart failure patients was systematically reviewed. Nine electronic databases were searched through the combination of synonyms for heart failure and sensitive filters for cost-effectiveness and early warning systems.

EXPERT COMMENTARY

The retrieved models show some variability with regards to their general study characteristics. Overall, they display satisfactory methodological quality, even though some points could be improved, namely on the consideration and discussion of any competing theories regarding model structure and disease progression, identification of key parameters and the use of expert opinion, and uncertainty analyses. A comprehensive definition of early warning systems and further research under this label should be pursued. To improve the transparency of economic evaluation publications, authors should make available detailed technical information regarding the published models.

Tracing the natural course of visual acuity and quality of life in neovascular age-related macular degeneration: a systematic review and quality of life study

Background

Describing the natural course of neovascular age-related macular degeneration (nAMD) is essential in discussing prognosis and treatment options with patients and to support cost-effectiveness studies.

Methods

First, we performed a literature search in PubMed, Embase, and Cochrane. We included randomized clinical trials and prospective observational studies reporting visual acuity (VA) in non-treated patients, 24 studies in total. We integrated VA data using best fit on Lineweaver-Burke plots and modelled with non-linear regression using reciprocal terms. Second, we performed a quality-of-life (QoL) study in nAMD patients. We measured VA with Radner reading charts and QoL with the Health Utilities Index issue 3 (HUI-3) questionnaire in 184 participants. We studied the relation VA-QoL with linear regression. Third, with Monte Carlo simulation, we integrated the VA model from the literature review and the relation VA-QoL from the QoL study.

Results

Visual acuity was 0.4 and 0.07 after 5 years in the better-seeing, and worse-seeing eye, respectively. After 4.3 years, VA was <0.5 in the better-seeing eye; <0.3 after 7 years; 0.05 after 17 years. QoL score decreased from 0.6 to 0.45 after 10 years.

Conclusions

The natural course of nAMD in both eyes needs to be considered when informing patients. Visual acuity in the best eye decreases to below 0.5 in 4.3 years. This affects QoL significantly.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-017-0514-3) contains supplementary material, which is available to authorized users.

Evaluation on the cost-effective threshold of osteoporosis treatment on elderly women in China using discrete event simulation model

This study used a simulation model to determine the cost-effective threshold of fracture risk to treat osteoporosis among elderly Chinese women. Osteoporosis treatment is cost-effective among average-risk women who are at least 75 years old and above-average-risk women who are younger than 75 years old.

INTRODUCTION

Aging of the Chinese population is imposing increasing economic burden of osteoporosis. This study evaluated the cost-effectiveness of osteoporosis treatment among the senior Chinese women population.

METHODS

A discrete event simulation model using age-specific probabilities of hip fracture, clinical vertebral fracture, wrist fracture, humerus fracture, and other fracture; costs (2015 US dollars); and quality-adjusted life years (QALYs) was used to assess the cost-effectiveness of osteoporosis treatment. Incremental cost-effectiveness ratio (ICER) was calculated. The willingness to pay (WTP) for a QALY in China was compared with the calculated ICER to decide the cost-effectiveness. To determine the absolute 10-year hip fracture probability at which the osteoporosis treatment became cost-effective, average age-specific probabilities for all fractures were multiplied by a relative risk (RR) that was systematically varied from 0 to 10 until the WTP threshold was observed for treatment relative to no intervention. Sensitivity analyses were also performed to evaluate the impacts from WTP and annual treatment costs.

RESULTS

In baseline analysis, simulated ICERs were higher than the WTP threshold among Chinese women younger than 75, but much lower than the WTP among the older population. Sensitivity analyses indicated that cost-effectiveness could vary due to a higher WTP threshold or a lower annual treatment cost. A 30 % increase in WTP or a 30 % reduction in annual treatment costs will make osteoporosis treatment cost-effective for Chinese women population from 55 to 85.

CONCLUSIONS

The current study provides evidence that osteoporosis treatment is cost-effective among a subpopulation of Chinese senior women. The results also indicate that the cost-effectiveness of using osteoporosis treatment is sensitive to the WTP threshold and annual treatment costs.

Expected lifetime numbers, risks, and burden of osteoporotic fractures for 50-year old Chinese women: a discrete event simulation incorporating FRAX

This work was undertaken to provide an estimation of expected lifetime numbers, risks, and burden of fractures for 50-year-old Chinese women. A discrete event simulation model was developed to simulate the lifetime fractures of 50-year-old Chinese women at average risk of osteoporotic fracture. Main events in the model included hip fracture, clinical vertebral fracture, wrist fracture, humerus fracture, and other fracture. Fracture risks were calculated using the FRAX^® tool. Simulations of 50-year-old Chinese women without fracture risks were also carried out as a comparison to determine the burden of fractures. A 50-year-old Chinese woman at average risk of fracture is expected to experience 0.135 (95 % CI: 0.134-0.137) hip fractures, 0.120 (95 % CI: 0.119-0.122) clinical vertebral fractures, 0.095 (95 % CI: 0.094-0.096) wrist fractures, 0.079 (95 % CI: 0.078-0.080) humerus fractures, and 0.407 (95 % CI: 0.404-0.410) other fractures over the remainder of her life. The residual lifetime risk of any fracture, hip fracture, clinical vertebral fracture, wrist fracture, humerus fracture, and other fracture for a 50-year-old Chinese woman is 37.36, 11.77, 10.47, 8.61, 7.30, and 27.80 %, respectively. The fracture-attributable excess quality-adjusted life year (QALY) loss and lifetime costs are estimated at 0.11 QALYs (95 % CI: 0.00-0.22 QALYs) and US $714.61 (95 % CI: US $709.20-720.02), totaling a net monetary benefit loss of US $1,104.43 (95 % CI: US $904.09-1,304.78). Chinese women 50 years of age are at high risk of osteoporotic fracture, and the expected economic and quality-of-life burden attributable to osteoporotic fractures among Chinese women is substantial.

More frequent, more costly? Health economic modelling aspects of monitoring glaucoma patients in England

BACKGROUND

Chronic open angle glaucoma (COAG) is an age-related eye disease causing irreversible loss of visual field (VF). Health service delivery for COAG is challenging given the large number of diagnosed patients requiring lifelong periodic monitoring by hospital eye services. Yet frequent examination better determines disease worsening and speed of VF loss under treatment. We examine the cost-effectiveness of increasing frequency of VF examinations during follow-up using a health economic model.

METHODS

Two different VF monitoring schemes defined as current practice (annual VF testing) and proposed practice (three VF tests per year in the first 2 years after diagnosis) were examined. A purpose written health economic Markov model is used to test the hypothesis that cost effectiveness improves by implementing proposed practice on groups of patients stratified by age and severity of COAG. Further, a new component of the model, estimating costs of visual impairment, was added. Results were derived from a simulated cohort of 10000 patients with quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) used as main outcome measures.

RESULTS

An ICER of £21,392 per QALY was derived for proposed practice improving to a value of £11,382 once savings for prevented visual impairment was added to the model. Proposed practice was more cost-effective in younger patients. Proposed practice for patients with advanced disease at diagnosis generated ICERs > £60,000 per QALY; these cases would likely be on the most intensive treatment pathway making clinical information on speed of VF loss redundant. Sensitivity analysis indicated results to be robust in relation to hypothetical willingness to pay threshold identified by national guidelines, although greatest uncertainty was allied to estimates of implementation and visual impairment costs.

CONCLUSION

Increasing VF monitoring at the earliest stages of follow-up for COAG appears to be cost-effective depending on reasonable assumptions about implementation costs. Our health economic model highlights benefits of stratifying patients to more or less monitoring based on age and stage of disease at diagnosis; a prospective study is needed to prove these findings. Further, this works highlights gaps in knowledge about long term costs of visual impairment.

The long term effectiveness and cost-effectiveness of initiating treatment for ocular hypertension

PURPOSE

To investigate the long-term health and economic consequences of direct treatment initiation in ocular hypertension patients.

METHODS

A cost-effectiveness analysis with a societal perspective and a lifelong horizon was performed. The primary outcomes were the incremental quality-adjusted life years (QALYs) and costs of direct pressure-lowering treatment for ocular hypertension, compared to a strategy where treatment is postponed until conversion to glaucoma has been observed. We used a decision analytic model based on individual patient simulation to forecast disease progression and treatment decisions in both strategies in a representative heterogeneous patient population and in 18 patient subgroups stratified by initial intraocular pressure and additional risk factors for conversion.

RESULTS

The incremental discounted health gain of direct treatment was 0.27 QALYs, whereas the incremental discounted costs were -€ 649 during an average lifetime of 26 years. In the simulations of patient subgroups, the model outcomes moved towards higher health gains and lower incremental costs with increasing risk of conversion in the patient population. The incremental cost-effectiveness ratio of direct treatment ranged from € 15,425 per QALY gained in the lowest-risk subgroup to dominance in the highest-risk subgroup. Probabilistic sensitivity analysis indicated that uncertainty surrounding the model input parameters did not affect the conclusions.

CONCLUSION

Direct, early, pressure-lowering treatment is a dominant cost-effective treatment strategy over a strategy to start the same treatment approach later, after glaucoma has occurred for patients with ocular hypertension. Its implementation and consequences should be discussed with ophthalmologists and individual patients.

When to use discrete event simulation (DES) for the economic evaluation of health technologies? A review and critique of the costs and benefits of DES

Modelling in economic evaluation is an unavoidable fact of life. Cohort-based state transition models are most common, though discrete event simulation (DES) is increasingly being used to implement more complex model structures. The benefits of DES relate to the greater flexibility around the implementation and population of complex models, which may provide more accurate or valid estimates of the incremental costs and benefits of alternative health technologies. The costs of DES relate to the time and expertise required to implement and review complex models, when perhaps a simpler model would suffice. The costs are not borne solely by the analyst, but also by reviewers. In particular, modelled economic evaluations are often submitted to support reimbursement decisions for new technologies, for which detailed model reviews are generally undertaken on behalf of the funding body. This paper reports the results from a review of published DES-based economic evaluations. Factors underlying the use of DES were defined, and the characteristics of applied models were considered, to inform options for assessing the potential benefits of DES in relation to each factor. Four broad factors underlying the use of DES were identified: baseline heterogeneity, continuous disease markers, time varying event rates, and the influence of prior events on subsequent event rates. If relevant, individual-level data are available, representation of the four factors is likely to improve model validity, and it is possible to assess the importance of their representation in individual cases. A thorough model performance evaluation is required to overcome the costs of DES from the users' perspective, but few of the reviewed DES models reported such a process. More generally, further direct, empirical comparisons of complex models with simpler models would better inform the benefits of DES to implement more complex models, and the circumstances in which such benefits are most likely.

Diagnosing Alzheimer's disease: a systematic review of economic evaluations

BACKGROUND

The objective of this study is to systematically review the literature on economic evaluations of interventions for the early diagnosis of Alzheimer's disease (AD) and related disorders and to describe their general and methodological characteristics. We focused on the diagnostic aspects of the decision models to assess the applicability of existing decision models for the evaluation of the recently revised diagnostic research criteria for AD.

METHODS

PubMed and the National Institute for Health Research Economic Evaluation database were searched for English-language publications related to economic evaluations on diagnostic technologies. Trial-based economic evaluations were assessed using the Consensus on Health Economic Criteria list. Modeling studies were assessed using the framework for quality assessment of decision-analytic models.

RESULTS

The search retrieved 2109 items, from which eight decision-analytic modeling studies and one trial-based economic evaluation met all eligibility criteria.

CONCLUSIONS

Diversity among the study objective and characteristics was considerable and, despite considerable methodological quality, several flaws were indicated. Recommendations were focused on diagnostic aspects and the applicability of existing models for the evaluation of recently revised diagnostic research criteria for AD.

Comparison of resource utilization in the treatment of open-angle glaucoma between two cities in Finland: is more better?

INTRODUCTION

Glaucoma is a progressive optic neuropathy associated with neural rim loss of the optic disc and the retinal nerve fibre layer typically causing visual field (VF) deterioration. Generally, glaucomatous lesions in the eye and in the visual field progress slowly over the years. In population-based cross-sectional studies, the percentage of unilateral or bilateral visual impairment varied between 3-12%. In screening studies, 0.03-2.4% of patients have been found to suffer visual impairment. Glaucoma has previously been associated with substantial healthcare costs and resource consumption attributable to the treatment of the disease. The disease also causes reduction in health-related quality of life (HRQoL) in patients with glaucoma.

OBJECTIVE AND METHODS

This study compares patients with diagnosed open-angle glaucoma from two geographically different regions in Finland. A total of 168 patients were examined, 85 subjects from an area with higher per patient treatment costs (Oulu) and 83 patients from a region with lower per patient treatment costs (Turku). All patients had a history of continuous glaucoma medication use for a period of 11 years. For each patient, the total direct costs from glaucoma treatment were calculated and the total amount of resource consumption was determined from registries and patient records. Each patient underwent a clinical examination with visual field assessment and fundus photography. These data were used to determine the current stage of disease for each patient. Health-related quality of life questionnaire (15D) was used in determining each patient's subjective HRQoL score.

RESULTS

When applying the current diagnostic criteria for open-angle glaucoma, a total of 40% of patients did not to display any structural or functional damage suggesting glaucoma after 11 years of continuous medical treatment and follow-up. Patients with higher glaucoma stage (worse disease) were found to have statistically higher treatment costs compared with those at lower disease stages. Resource consumption was also greater in the patients in higher glaucoma stage. Patients in the Oulu district consumed more resources, and glaucoma treatment was more expensive than in the Turku area. The total treatment cost in Oulu and Turku was 6010 € and 4452 €, respectively, for the whole 11-year period. There was no statistically significant difference in quality-of-life scores between the two areas. No difference was noted between the higher-spending and lower-spending areas in this respect. However, when the population was analysed as a whole, patients with higher glaucoma stage were found to have lower vision-based 15D scores compared with those at lower disease stages. This observation was made also at both districts independently.

CONCLUSIONS

Major cost source in open-angle glaucoma treatment is medication, up to 74% of annual costs. In addition, it seems that higher resource consumption and higher treatment costs do not increase the patients' HRQoL as assessed by the 15D instrument.

The long-term outcomes of four alternative treatment strategies for primary open-angle glaucoma

PURPOSE

To evaluate the long-term effects and costs of four treatment strategies for primary open-angle glaucoma compared to usual care.

METHODS

Cost-effectiveness analyses with a lifelong horizon were made from a societal perspective. Data were generated with a patient-level model based on discrete event simulation. The model structure and parameter estimates were based on literature, particularly clinical studies on the natural course of glaucoma and the effect of treatment. We simulated heterogeneous cohorts of 3000 patients and explored the impact of uncertainty with sensitivity analyses.

RESULTS

The incremental cost-effectiveness ratio (ICER) of initial treatment with a prostaglandin analogue compared with a β-blocker was €12.931 per quality-adjusted life year (QALY) gained. A low initial target pressure (15 mmHg) resulted in 0.115 QALYs gained and €1550 saved compared to a gradual decrease from 21 to 15 mmHg upon progression. Visual field (VF) measurements every 6 rather than 12 months lead to health gains at increased costs (ICER €173,486 per QALY gained), whereas measurements every 24 months lead to health losses at reduced costs (ICER €21,516 per QALY lost). All treatment strategies were dominant over 'withholding treatment'.

CONCLUSIONS

From a cost-effectiveness point of view, it seems advantageous to aim for a low intraocular pressure in all glaucoma patients. The feasibility of this strategy should therefore be investigated. Additionally, the cost-effectiveness outcomes of initiating monotherapy with a prostaglandin analogue and reducing the frequency of VF testing may be acceptable.

The role of the expected value of individualized care in cost-effectiveness analyses and decision making

OBJECTIVE

To explore the feasibility and potential role of the expected value of individualized care (EVIC) framework.

METHODS

The EVIC quantifies how much benefits are forgone when a treatment decision is based on the best-expected outcomes in the population rather than in the individual patient. We have reviewed which types of patient-level attributes contribute to the EVIC and how they affect the interpretation of the outcomes. In addition, we have applied the EVIC framework to the outcomes of a microsimulation-based cost-effectiveness analysis for glaucoma treatment.

RESULTS

For EVIC outcomes to inform decisions about clinical practice, we need to calculate the parameter-specific EVIC of known or knowable patient-level attributes and compare it with the real costs of implementing individualized care. In the case study, the total EVIC was €580 per patient, but patient-level attributes known at treatment decision had minimal impact. A subgroup policy based on individual disease progression could be worthwhile if a predictive test for glaucoma progression could be developed and implemented for less than €130 per patient.

CONCLUSIONS

The EVIC framework is feasible in cost-effectiveness analyses and can be informative for decision making. The EVIC outcomes are particularly informative when they are (close to) zero. When the EVIC has a high value, implications depend on the type of patient-level attribute. EVIC can be a useful tool to identify opportunities to improve efficiency in health care by individualization of care and to quantify the maximal investment opportunities for implementing subgroup policy.

Economic considerations of the diagnosis and management for glaucoma in the developed world

PURPOSE OF REVIEW

This review evaluates the last 18-month literature related to costs and glaucoma. The emphasis is to look at evidence as a big picture and evaluate the critical points and challenges in methodology, current knowledge and future research.

RECENT FINDINGS

On the basis of simulation models, treating glaucoma appears to be cost-effective compared with no treatment. The results of the simulation models are, however, not consistent regarding when to treat ocular hypertension and when comparing different therapeutic interventions. Most models simulated starting treatment with prostaglandins compared with other medications, whereas one study simulated also initial laser therapy which appeared to be cost saving compared with medical therapy. The models utilized input data both from randomized controlled trials (ideal outcomes) and observational studies (with incomplete and selective reporting). Models suffer from unreliability of data, for example data from randomized diagnostic trials, empirical data of utility values and glaucoma-induced visual disability are limited.

SUMMARY

As the number of economic evaluations increases, the interpretation and evaluation of their extensive reporting appears very challenging. The published studies highlight the range of uncertainties due to the shortages of our current knowledge and evidence. There is a need for reliable and 'realistic' data for economic evaluations, preferably data from pragmatic randomized trials of 'usual patients'. Similar to emphasizing the cost-effectiveness of care, there is a need to evaluate the expected payback and cost-effectiveness of research interventions. However, even high-quality evidence cannot help our patients if we do not adopt cost-effective interventions.

Discrete event simulation: the preferred technique for health economic evaluations?

OBJECTIVES

To argue that discrete event simulation should be preferred to cohort Markov models for economic evaluations in health care.

METHODS

The basis for the modeling techniques is reviewed. For many health-care decisions, existing data are insufficient to fully inform them, necessitating the use of modeling to estimate the consequences that are relevant to decision-makers. These models must reflect what is known about the problem at a level of detail sufficient to inform the questions. Oversimplification will result in estimates that are not only inaccurate, but potentially misleading.

RESULTS

Markov cohort models, though currently popular, have so many limitations and inherent assumptions that they are inadequate to inform most health-care decisions. An event-based individual simulation offers an alternative much better suited to the problem. A properly designed discrete event simulation provides more accurate, relevant estimates without being computationally prohibitive. It does require more data and may be a challenge to convey transparently, but these are necessary trade-offs to provide meaningful and valid results.

CONCLUSION

In our opinion, discrete event simulation should be the preferred technique for health economic evaluations today.