Greg Zaric

• Naderi, B.; Begen, M. A.; Zaric, G. S., (Forthcoming), "Type-2 integrated process-planning and scheduling problem: Reformulation and solution algorithms", Computers and Operations Research
  Abstract: We study the type-2 integrated process-planning and scheduling (IPPS) problem where each job is represented by a directed network graph. To the best of our knowledge, there is only one mathematical model in the literature implementing the type-2 IPPS partially, and the solution methods available for this problem are all based on heuristics and metaheuristics. We introduce three properties that enable us to fully formulate all aspects of the type-2 IPPS problem with a mathematical programming model for the first time. To solve our model, we develop a logic-based Benders decomposition method hybridized with constraint programming. We decompose the problem into two smaller ones such that we can use the best solution technique for each one, master problem and subproblem. To enhance our solution approach, we incorporate a combinatorial relaxation of subproblem into the master problem. We evaluate our method using a well-known benchmark including 24 instances and compare its performance with six existing solution methods solving the same benchmark. We solve all the 24 instances of this benchmark to optimality where seven of these 24 instances are solved to optimality for the first time. We also generate a new set of 144 larger instances to further evaluate our solution methods and provide insights on when each method performs better.
• Strohbehn, G. W.; Cooperrider, J. H.; Yang, D.; Fendrick, A. M.; Ratain, M. J.; Zaric, G. S., 2022, "Pfizer and Palbociclib in China: Analyzing an Oncology Pay-for-Performance Plan", Value in Health Regional Issues, September 31: 34 - 38.
• Reid, G. J.; Stewart, S. L.; Barwick, M.; Cunningham, C.; Carter, J.; Evans, B.; Leschied, A.; Neufeld, R. W. J.; St. Pierre, J.; Tobon, J., et al., (Forthcoming), "Exploring Patterns of Service Utilization Within Children’s Mental Health Agencies", Journal of Child and Family Studies
  Abstract: The natural history of psychopathology indicates that many children will re-experience mental health problems. However, little is known about service use over extended time periods. We explored service use of a 5-year time period, and expected to find that some children received mental health services for many months, and some received services in episodes. Administrative visit data from 6 child and youth mental health service agencies and over 7000 children, 4 to 11 years old at their first visit in 2000–2003, were analyzed. Episodes of care were coded based on having a minimum of three visits with 180-day free period between episodes. Chart reviews were conducted for a stratified random sample of 319 cases to obtain clinical and demographic sample characteristics not available in the administrative data. Five patterns of service use were identified in 5 years of visit data using latent class cluster analyses. Close to a third of children were involved for longer than a year, and 19% received two or more episodes of care within the 5-year study period. Children who had patterns of service use with long durations of involvement tended to have a higher percentage of cases with child welfare involvement, and children had fewer strengths in terms of relationships with peers and adults, and abilities to manage negative life experiences. Best methods of caring for children with ongoing or episodic problems need to be developed, and we need to improve methods for identifying those children who might benefit from alternative models of care.

  Link(s) to publication:

  http://dx.doi.org/10.1007/s10826-020-01859-2

• Ghamat, S.; Zaric, G. S.; Pun, H., 2021, "Care-coordination: Gain-sharing Agreements in Bundled Payment Models", Production and Operations Management, June 30(5): 1457 - 1474.
  Abstract: We study gain-sharing agreements in a target price-minimum quality payment system. Our work is inspired by the Centers for Medicare and Medicaid Services’ (CMS) Comprehensive Care for Joint Replacement (CJR) bundled payment model. In our model, patients receive care from a hospital and a post-acute care provider. A third-party payer establishes target levels for total billing by the hospital and provider, and a target on the overall quality of care. The hospital and provider receive fee-for-service (FFS) billings during an episode of care, defined as the period that starts with an admission of a patient to the hospital and ends 90 days post-discharge. The hospital may also receive an incentive payment if total FFS billing by both parties is below the target price and total quality by both parties is above the minimum quality. The goal of the incentive payment is to encourage hospitals to enter into “gain-sharing” agreements with providers. We model the interactions between the three parties. We show that while using a gain-sharing agreement might be a “win-win-win” scenario for the three parties, good design of the payment scheme by the payer is essential to incentivize a hospital to participate in the bundled payment model (e.g., CJR) and sign a gain-sharing agreement with the provider. Furthermore, we illustrate that a target price-minimum quality bundled payment model would be more effective, in care-coordination, in healthcare settings where the provider is much more effective than the hospital in reducing its billing.

  Link(s) to publication:

  http://dx.doi.org/10.1111/poms.13332

• Bamimore, M. A.; Devlin, R. A.; Zaric, G. S.; Garg, A. X.; Sarma, S., 2021, "Quality of Diabetes Care in Blended Fee-for-Service and Blended Capitation Payment Systems", Canadian Journal of Diabetes, April 45(3): 261 - 268.
  Abstract: © 2020 Canadian Diabetes Association Objectives: In the middle to late 2000s, many family physicians switched from a Family Health Group (FHG; a blended fee-for-service model) to a Family Health Organization (FHO; a blended capitation model) in Ontario, Canada. The evidence on the link between physician remuneration schemes and quality of diabetes care is mixed in the literature. We examined whether physicians who switched from the FHG to FHO model provided better care for individuals living with diabetes relative to those who remained in the FHG model. Methods: Using longitudinal health administrative data from 2006 to 2016, we investigated the impact of physicians switching from FHG to FHO on 8 quality indicators related to diabetes care. Because FHO physicians are likely to be systematically different from FHGs, we employed propensity-score-based inverse probability-weighted fixed-effects regression models. All analyses were conducted at the physician level. Results: We found that FHO physicians were more likely to provide glycated hemoglobin testing by 2.75% (95% confidence interval [CI], 1.89% to 3.60%), lipid assessment by 2.76% (CI, 1.95% to 3.57%), nephropathy screening by 1.08% (95% CI, 0.51% to 1.66%) and statin prescription by 1.08% (95% CI, 0.51% to 1.66%). Patients under FHOs had a lower estimated risk of mortality by 0.0124% (95% CI, 0.0123% to 0.0126%) per physician per year. However, FHG and FHO physicians were similar for annual eye examination, prescription of angiotensin-converting enzyme inhibitors (or angiotensin II receptor blockers) and patients’ risk of avoidable diabetes-related hospitalizations. Conclusions: Compared with blended fee-for-service, blended capitation payment is associated with a small, but statistically significant, improvement in some aspects of diabetes care.

  Link(s) to publication:

  http://dx.doi.org/10.1016/j.jcjd.2020.09.002

• Qu, X. M.; Chen, Y.; Zaric, G. S.; Senan, S.; Olson, R. A.; Harrow, S.; John-Baptiste, A.; Gaede, S.; Mulroy, L. A.; Schellenberg, D., et al., 2021, "Is SABR Cost-Effective in Oligometastatic Cancer? An Economic Analysis of the SABR-COMET Randomized Trial", International Journal of Radiation Oncology Biology Physics, April 109(5): 1176 - 1184.
  Abstract: The phase 2 randomized study SABR-COMET demonstrated that in patients with controlled primary tumors and 1 to 5 oligometastatic lesions, SABR was associated with improved progression-free survival (PFS) compared with standard of care (SoC), but with higher costs and treatment-related toxicities. The aim of this study was to assess the cost-effectiveness of SABR versus SoC in this setting. Methods and Materials: A Markov model was constructed to perform a cost-utility analysis from the Canadian health care system perspective. Utility values and transition probabilities were derived from individual-level data from the SABR-COMET trial. One-way, 2-way, and probabilistic sensitivity analyses were performed. Costs were expressed in 2018 CAD. A separate analysis based on US payer's perspective was performed. An incremental cost-effectiveness ratio (ICER) at a willingness-to-pay threshold of $100,000 per quality-adjusted life year (QALY) was used. Results: In the base case scenario, SABR was cost-effective at an ICER of $37,157 per QALY gained. This finding was most sensitive to the number of metastatic lesions treated with SABR (ICER: $28,066 per QALY for 2, increasing to $64,429 per QALY for 5), difference in chemotherapy use (ICER: $27,173-$53,738 per QALY), and PFS hazard ratio (HR) between strategies (ICER: $31,548-$53,273 per QALY). Probabilistic sensitivity analysis revealed that SABR was cost-effective in 97% of all iterations. Two-way sensitivity analysis demonstrated a nonlinear relationship between the number of lesions and the PFS HR. To maintain cost-effectiveness for each additional metastasis, the HR must decrease by approximately 0.047. The US cost analysis yielded similar results, with an ICER of $54,564 (2018 USD per QALY) for SABR. Conclusions: SABR is cost-effective for patients with 1 to 5 oligometastatic lesions compared with SoC.

  Link(s) to publication:

  http://dx.doi.org/10.1016/j.ijrobp.2020.12.001

• Schraeder, K. E.; Barwick, M.; Cairney, J.; Carter, J.; Kurdyak, P.; Neufeld, R. W. J.; Stewart, S. L.; Pierre, J. S.; Tobon, J.; Vingilis, E., et al., 2021, "Re-accessing mental health care after age 18: A longitudinal cohort study of youth involved with community-based child and youth mental health agencies in Ontario", Journal of the Canadian Academy of Child and Adolescent Psychiatry, February 30(1): 12 - 24.
  Abstract: Objective: About 20-26% of children and youth with a mental health disorder (depending on age and respondent) report receiving services from a community-based Child and Youth Mental Health (CYMH) agency. However, because agencies have an upper age limit of 18-years old, youth requiring ongoing mental health services must “transition” to adult-oriented care. General healthcare providers (e.g., family physicians) likely provide this care. The objective of this study was to compare the likelihood of receiving physician-based mental health services after age 18 between youth who had received community-based mental health services and a matched population sample. Method: A longitudinal matched cohort study was conducted in Ontario, Canada. A CYMH cohort that received mental health care at one of five CYMH agencies, aged 7-14 years at their first visit (N=2,822), was compared to age, sex, region-matched controls (N=8,466). Results: CYMH youth were twice as likely as the comparison sample to have a physician-based mental health visit (i.e., by a family physician, pediatrician, psychiatrists) after age 18; median time to first visit was 3.3 years. Having a physician mental health visit before age 18 was associated with a greater likelihood of experiencing the outcome than community-based CYMH services alone. Conclusion: Most youth involved in community-based CYMH agencies will re-access services from physicians as adults. Youth receiving mental health services only within community agencies, and not from physicians, may be less likely to receive physician-based mental health services as adults. Collaboration between CYMH agencies and family physicians may be important for youth who require ongoing care into adulthood.
• Hong, M.; Thind, A.; Zaric, G. S.; Sarma, S., 2021, "Emergency department use following incentives to provide after-hours primary care: A retrospective cohort study", Canadian Medical Association Journal, January 193(3): E85 - E93.
  Abstract: BACKGROUND: Access to primary care outside of regular working hours is limited in many countries. This study investigates the relation between the after-hours premium, an incentive for primary care physicians to provide services after hours, and less-urgent visits to the emergency department in Ontario, Canada. METHODS: We analyzed a retrospective cohort of a random sample of Ontario residents from April 2002 to March 2006, and a subcohort of patients followed from April 2005 to March 2016. We linked patient and primary care physician data with emergency department visit data. We used fixed-effects regression models to analyze the association between the introduction of the after-hours premium, as well as subsequent increases in the value of the premium, and the number of monthly emergency department visits. RESULTS: The sample consisted of 586 534 patients between 2002 and 2006, and 201 594 patients from 2005 to 2016. After controlling for patient and physician characteristics, seasonality and time-invariant patient confounding factors, introduction of the after-hours premium was associated with a reduction of 1.26 less-urgent visits to the emergency department per 1000 patients per month (95% confidence interval -1.48 to -1.04). Most of this reduction was observed in after-hours visits. Sensitivity analysis showed that the monthly reduction in less-urgent visits to the emergency department was in the range of -1.24 to -1.16 per 1000 patients. Subsequent increases in the after-hours premium were associated with a small reduction in less-urgent visits to the emergency department. INTERPRETATION: Ontario's experience suggests that incentivizing physicians to improve access to after-hours primary care reduces some less-urgent visits to the emergency department. Other jurisdictions may consider incentives to limit less-urgent visits to the emergency department.

  Link(s) to publication:

  http://dx.doi.org/10.1503/cmaj.200277

• Zaric, G. S., 2021, "How Risky Is That Risk Sharing Agreement? Mean-Variance Tradeoffs and Unintended Consequences of Six Common Risk Sharing Agreements", Medical Decision Making: Policy & Practice, January 6(1): 238146832199040 - 238146832199040.
  Abstract: Background. Pharmaceutical risk sharing agreements (RSAs) are commonly used to manage uncertainties in costs and/or clinical benefits when new drugs are added to a formulary. However, existing mathematical models of RSAs ignore the impact of RSAs on clinical and financial risk. Methods. We develop a model in which the number of patients, total drug consumption per patient, and incremental health benefits per patient are uncertain at the time of the introduction of a new drug. We use the model to evaluate the impact of six common RSAs on total drug costs and total net monetary benefit (NMB). Results. We show that, relative to not having an RSA in place, each RSA reduces expected total drug costs and increases expected total NMB. Each RSA also improves two measures of risk by reducing the probability that total drug costs exceed any threshold and reducing the probability of obtaining negative NMB. However, the effects on variance in both NMB and total drug costs are mixed. In some cases, relative to not having an RSA in place, implementing an RSA can increase variability in total drug costs or total NMB. We also show that, for some RSAs, when their parameters are adjusted so that they have the same impact on expected total drug cost, they can be rank-ordered in terms of their impact on variance in drug costs. Conclusions. Although all RSAs reduce expected total drug costs and increase expected total NMB, some RSAs may actually have the undesirable effect of increasing risk. Payers and formulary managers should be aware of these mean-variance tradeoffs and the potentially unintended results of RSAs when designing and negotiating RSAs.

  Link(s) to publication:

  http://dx.doi.org/10.1177/2381468321990404

• Thavam, T.; Devlin, R. A.; Thind, A.; Zaric, G. S.; Sarma, S., 2020, "The impact of the diabetes management incentive on diabetes-related services: evidence from Ontario, Canada", European Journal of Health Economics, December 21(9): 1279 - 1293.
  Abstract: Financial incentives have been introduced in several countries to improve diabetes management. In Ontario, the most populous province in Canada, a Diabetes Management Incentive (DMI) was introduced to family physicians practicing in patient enrollment models in 2006. This paper examines the impact of the DMI on diabetes-related services provided to individuals with diabetes in Ontario. Longitudinal health administrative data were obtained for adults diagnosed with diabetes and their family physicians. The study population consisted of two groups: DMI group (patients enrolled with a family physician exposed to DMI for 3 years), and comparison group (patients affiliated with a family physician ineligible for DMI throughout the study period). Diabetes-related services was measured using the Diabetic Management Assessment (DMA) billing code claimed by patient’s physician. The impact of DMI on diabetes-related services was assessed using difference-in-differences regression models. After adjusting for patient- and physician-level characteristics, patient fixed-effects and patient-specific time trend, we found that DMI increased the probability of having at least one DMA fee code claimed by patient’s physician by 9.3% points, and the probability of having at least three DMA fee codes claimed by 2.1% points. Subgroup analyses revealed the impact of DMI was slightly larger in males compared to females. We found that Ontario’s DMI was effective in increasing the diabetes-related services provided to patients diagnosed with diabetes in Ontario. Financial incentives for physicians help improve the provision of targeted diabetes-related services.

  Link(s) to publication:

  http://dx.doi.org/10.1007/s10198-020-01216-6

• Somé, N. H.; Devlin, R. A.; Mehta, N.; Zaric, G. S.; Sarma, S., 2020, "Team-based primary care practice and physician's services: Evidence from Family Health Teams in Ontario, Canada", Social Science and Medicine, November 264: 113310 - 113310.
  Abstract: Team-based primary care offers a wide range of health services to patients by using interdisciplinary health care providers committed to delivering comprehensive, coordinated and high-quality care through team collaboration. Ontario's Family Health Team (FHT), the largest team-based practice model in Canada, was introduced to improve access to and effectiveness of primary health care services, and was available primarily for physicians paid under blended capitation models (Family Health Organizations and Family Health Networks). Using health administrative data on physicians practicing under blended capitation models in Ontario between 2006 and 2015, we study the impact of switching from non-FHT to FHTs on the production of capitated comprehensive care services, after-hours services, non-incentivized services, and services provided to non-enrolled patients by family physicians. We find that when in FHTs, physicians increase the production of total services and non-incentivized services by 26% and 5% per annum and reduce capitated comprehensive care services by 3.2% per annum. When in FHTs, physicians also see and enroll more patients relative to those practicing in non-FHTs. We find evidence of improved access to physician's services under team-based primary care, but switching to FHTs has no effect on the production of after-hours services and services provided to non-enrolled patients.

  Link(s) to publication:

  http://dx.doi.org/10.1016/j.socscimed.2020.113310

• Somé, N. H.; Devlin, R. A.; Mehta, N.; Zaric, G. S.; Sarma, S., 2020, "Stirring the pot: Switching from blended fee-for-service to blended capitation models of physician remuneration", HEALTH ECONOMICS, November 29(11): 1435 - 1455.
  Abstract: In Canada's most populous province, Ontario, family physicians may choose between the blended fee-for-service (Family Health Group [FHG]) and blended capitation (Family Health Organization [FHO] payment models). Both models incentivize physicians to provide after-hours (AH) and comprehensive care, but FHO physicians receive a capitation payment per enrolled patient adjusted for age and sex, plus a reduced fee-for-service while FHG physicians are paid by fee-for-service. We develop a theoretical model of physician labor supply with multitasking to predict their behavior under FHG and FHO, and estimable equations are derived to test the predictions empirically. Using health administrative data from 2006 to 2014 and a two-stage estimation strategy, we study the impact of switching from FHG to FHO on the production of a capitated basket of services, after-hours services and nonincentivized services. Our results reveal that switching from the FHG to FHO reduces the production of capitated services to enrolled patients and services to nonenrolled patients by 15% and 5% per annum and increases the production of after-hours and nonincentivized services by 8% and 15% per annum.

  Link(s) to publication:

  http://dx.doi.org/10.1002/hec.4145

• Hong, M.; Thind, A.; Zaric, G. S.; Sarma, S., 2020, "The impact of improved access to after-hours primary care on emergency department and primary care utilization: A systematic review", Health Policy, August 124(8): 812 - 818.
  Abstract: Access to after-hours primary care is problematic in many developed countries, leading patients to instead visit the emergency department for non-urgent conditions. However, emergency department utilization for conditions treatable in primary care settings may contribute to emergency department overcrowding and increased health system costs. This systematic review examines the impact of various initiatives by developed countries to improve access to after-hours primary care on emergency department and primary care utilization. We performed a systematic review on the impact of improved access to after-hours primary and searched CINAHL, EMBASE, MEDLINE, and Scopus. We identified 20 studies that examined the impact of improved access to after-hours primary care on ED utilization and 6 studies that examined the impact on primary care utilization. Improved access to after-hours primary care was associated with increased primary care utilization, but had a mixed effect on emergency department utilization, with limited evidence of a reduction in non-urgent and semi-urgent emergency department visits. Although our review suggests that improved access to after-hours primary care may limit emergency department utilization by shifting patient care from the emergency department back to primary care, rigorous research in a given institutional context is required before introducing any initiative to improve access to after-hours primary care.

  Link(s) to publication:

  http://dx.doi.org/10.1016/j.healthpol.2020.05.015

• Hannouf, M. B.; Zaric, G. S.; Blanchette, P.; Brezden-Masley, C.; Paulden, M.; McCabe, C.; Raphael, J.; Brackstone, M., 2020, "Cost-effectiveness analysis of multigene expression profiling assays to guide adjuvant therapy decisions in women with invasive early-stage breast cancer", Pharmacogenomics Journal, February 20(1): 27 - 46.
  Abstract: Gene expression profiling (GEP) testing using 12-gene recurrence score (RS) assay (EndoPredict®), 58-gene RS assay (Prosigna®), and 21-gene RS assay (Oncotype DX®) is available to aid in chemotherapy decision-making when traditional clinicopathological predictors are insufficient to accurately determine recurrence risk in women with axillary lymph node-negative, hormone receptor-positive, and human epidermal growth factor-receptor 2-negative early-stage breast cancer. We examined the cost-effectiveness of incorporating these assays into standard practice. A decision model was built to project lifetime clinical and economic consequences of different adjuvant treatment-guiding strategies. The model was parameterized using follow-up data from a secondary analysis of the Anastrozole or Tamoxifen Alone or Combined randomized trial, cost data (2017 Canadian dollars) from the London Regional Cancer Program (Canada) and secondary Canadian sources. The 12-gene, 58-gene, and 21-gene RS assays were associated with cost-effectiveness ratios of $36,274, $48,525, and $74,911/quality-adjusted life year (QALY) gained and resulted in total gains of 379, 284.3, and 189.5 QALYs/year and total budgets of $12.9, $14.2, and $16.6 million/year, respectively. The total expected-value of perfect information about GEP assays’ utility was $10.4 million/year. GEP testing using any of these assays is likely clinically and economically attractive. The 12-gene and 58-gene RS assays may improve the cost-effectiveness of GEP testing and offer higher value for money, although prospective evidence is still needed. Comparative field evaluations of GEP assays in real-world practice are associated with a large societal benefit and warranted to determine the optimal and most cost-effective assay for routine use.

  Link(s) to publication:

  http://dx.doi.org/10.1038/s41397-019-0089-x

• Some, N.; Devlin, R. A.; Mehta, N.; Zaric, G. S.; Li, L.; Shariff, S.; Belhadji, B.; Thind, A.; Garg, A.; Sarma, S., et al., 2019, "Production of Physician Services under Fee-For-Service and Blended Fee-For-Service: Evidence from Ontario, Canada", Health Economics, December 28(12): 1418 - 1434.
  Abstract: We examine family physicians' responses to financial incentives for medical services in Ontario, Canada. We use administrative data covering 2003–2008, a period during which family physicians could choose between the traditional fee for service (FFS) and blended FFS known as the Family Health Group (FHG) model. Under FHG, FFS physicians are incentivized to provide comprehensive care and after‐hours services. A two‐stage estimation strategy teases out the impact of switching from FFS to FHG on service production. We account for the selection into FHG using a propensity score matching model, and then we use panel‐data regression models to account for observed and unobserved heterogeneity. Our results reveal that switching from FFS to FHG increases comprehensive care, after‐hours, and nonincentivized services by 3%, 15%, and 4% per annum. We also find that blended FFS physicians provide more services by working additional total days as well as the number of days during holidays and weekends. Our results are robust to a variety of specifications and alternative matching methods. We conclude that switching from FFS to blended FFS improves patients' access to after‐hours care, but the incentive to nudge service production at the intensive margin is somewhat limited.

  Link(s) to publication:

  http://dx.doi.org/10.1002/hec.3951

For more publications please see our Research Database