Robust implementation in general mechanisms

A social choice function is robustly implemented if every equilibrium on every type space achieves outcomes consistent with it. We identify a robust monotonicity condition that is necessary and (with mild extra assumptions) sufficient for robust implementation.Robust monotonicity is strictly stronger than both Maskin monotonicity (necessary and almost sufficient for complete information implementation) and ex post monotonicity (necessary and almost sufficient for ex post implementation). It is equivalent to Bayesian monotonicity on all type spaces.     

α‐SERIAL MECHANISMS FOR THE PROVISION OF AN EXCLUDABLE PUBLIC GOOD

We present a new class of “α‐serial mechanisms” for the provision of an excludable public good. Those mechanisms have a similar structure to the serial mechanism, but may let the non‐consumers pay a positive cost. They inherit desirable properties such as anonymity, envy‐freeness, Maskin monotonicity, and population monotonicity from the serial mechanism. We calculate the “maximal efficiency loss” and “maximal manipulation” of α‐serial mechanisms and point out a trade‐off between these two properties.     

An alternative characterization of top trading cycles

This paper introduces two new characterizations of the top trading cycles algorithm. The key to our characterizations is a new condition, independence of irrelevant rankings (IIR). Intuitively, a mechanism satisfies IIR if whenever an agent’s ranking at an object is irrelevant to her assignment, then it is irrelevant to the assignment of all agents. We demonstrate that a mechanism is Pareto efficient, strategy-proof, IIR, and satisfies mutual best if and only if it is top trading cycles. This provides a new insight into what distinguishes top trading cycles from all other efficient and strategy-proof assignment mechanisms. We provide a second characterization in terms of weak Maskin monotonicity. A mechanism satisfies Pareto efficiency, weak Maskin monotonicity, IIR, and mutual best if and only if it is top trading cycles. This allows us to directly compare top trading cycles to known characterizations of the deferred acceptance algorithm in terms of weak Maskin monotonicity.     

Healthcare costs for Crohn’s disease patients treated with infliximab: a propensity weighted comparison of the effects of treatment adherence

Objective:

The objective for the research was to evaluate the direct healthcare costs for Crohn’s disease (CD) patients categorized by adherence status.

Methods:

Adult patients with ≥1 claim for infliximab and ≥2 claims for CD who were continuously insured for 12 months before and after their first infliximab infusion (index date) were identified in a 2006–2009 US managed care database. Patients were excluded if they had rheumatoid arthritis claims, received infliximab billed as a pharmacy benefit, or received another biologic drug. Patients were categorized as being either adherent or intermittently adherent to infliximab using a pre-defined algorithm. Total and component direct costs, CD-related costs, rates of surgery, and days of hospitalization were estimated for the 360-day post-index period. Propensity weighted generalized linear models were used to adjust the cost estimates for potential confounding variables.

Results:

The total propensity weighted cost for infliximab adherent patients was $40,425 (95% CI?=?[$38,686, $42,242]), compared to $41,082 (95% CI?=?[$38,163, $44,223]) for the intermittently adherent (p?=?0.71). However, adherent patients had lower total direct medical costs, exclusive of infliximab, that were $13,097 (95% CI?=?[$12,141, $14,127]) compared with $20,068 (95% CI?=?[$17,676, $22,784]) for intermittently adherent patients as a result of substantially lower hospital and outpatient costs (p?Conclusions:

Greater drug-related costs for infliximab adherent patients were offset by lower costs from hospitalization and outpatient visits. These findings indicate that adherent patients have improved clinical outcomes, at a similar aggregate cost, than patients who are only intermittently adherent to therapy.     

Quantifying the defensive medicine contribution to primary care costs

Background:

Defensive medicine represents one cause of economic losses in healthcare. Studies that measured its cost have produced conflicting results.

Objective:

To directly measure the proportion of primary care costs attributable to defensive medicine.

Research design and methods:

Six-week prospective study of primary care physicians from four outpatient practices. On 3 distinct days, participants were asked to rate each order placed the day before on the extent to which it represented defensive medicine, using a 5-point scale from 0 (not at all defensive) to 4 (entirely defensive).

Main outcome measures:

This study calculated the order defensiveness score for each order (the defensiveness/4) and the physician defensive score (the mean of all orders defensiveness scores). Each order was assigned a weighted cost by multiplying the total cost of that order (based on Medicare reimbursement rates) by the order defensiveness score. The proportion of total cost attributable to defensive medicine was calculated by dividing the weighted cost of defensive orders by the total cost of all orders.

Results:

Of 50 eligible physicians, 23 agreed to participate; 21 returned the surveys and rated 1234 individual orders on 347 patients. Physicians wrote an average of 3.6?±?1.0 orders/visit with an associated total cost of $72.60?±?18.5 per order. Across physicians, the median physician defensive score was 0.018 (IQR?=?[0.008, 0.049]) and the proportion of costs attributable to defensive medicine was 3.1% (IQR?=?[0.5%, 7.2%]). Physicians with defensive scores above vs below the median had a similar number of orders and total costs per visit. Physicians were more likely to place defensive orders if trained in community hospitals vs academic centers (OR?=?4.29; 95% CI?=?1.55–11.86; p?=?0.01).

Conclusions:

This study describes a new method to directly quantify the cost of defensive medicine. Defensive medicine appears to have minimal impact on primary care costs.     

Weak monotonicity and Bayes–Nash incentive compatibility

An allocation rule is called Bayes–Nash incentive compatible, if there exists a payment rule, such that truthful reports of agents' types form a Bayes–Nash equilibrium in the direct revelation mechanism consisting of the allocation rule and the payment rule. This paper provides a characterization of Bayes–Nash incentive compatible allocation rules in social choice settings where agents have multi-dimensional types, quasi-linear utility functions and interdependent valuations. The characterization is derived by constructing complete directed graphs on agents' type spaces with cost of manipulation as lengths of edges. Weak monotonicity of the allocation rule corresponds to the condition that all 2-cycles in these graphs have non-negative length. For the case that type spaces are convex and the valuation for each outcome is a linear function in the agent's type, we show that weak monotonicity of the allocation rule together with an integrability condition is a necessary and sufficient condition for Bayes–Nash incentive compatibility.     

Distribution and drivers of costs in type 2 diabetes mellitus treated with oral hypoglycemic agents: a retrospective claims data analysis

Objective:

To describe the distribution of costs and to identify the drivers of high costs among adult patients with type 2 diabetes mellitus (T2DM) receiving oral hypoglycemic agents.

Methods:

T2DM patients using oral hypoglycemic agents and having HbA1c test data were identified from the Truven MarketScan databases of Commercial and Medicare Supplemental insurance claims (2004–2010). All-cause and diabetes-related annual direct healthcare costs were measured and reported by cost components. The 25% most costly patients in the study sample were defined as high-cost patients. Drivers of high costs were identified in multivariate logistic regressions.

Results:

Total 1-year all-cause costs for the 4104 study patients were $55,599,311 (mean cost per patient?=?$13,548). Diabetes-related costs accounted for 33.8% of all-cause costs (mean cost per patient?=?$4583). Medical service costs accounted for the majority of all-cause and diabetes-related total costs (63.7% and 59.5%, respectively), with a minority of patients incurring >80% of these costs (23.5% and 14.7%, respectively). Within the medical claims, inpatient admission for diabetes-complications was the strongest cost driver for both all-cause (OR?=?13.5, 95% CI?=?8.1–23.6) and diabetes-related costs (OR?=?9.7, 95% CI?=?6.3–15.1), with macrovascular complications accounting for most inpatient admissions. Other cost drivers included heavier hypoglycemic agent use, diabetes complications, and chronic diseases.

Limitations:

The study reports a conservative estimate for the relative share of diabetes-related costs relative to total cost. The findings of this study apply mainly to T2DM patients under 65 years of age.

Conclusions:

Among the T2DM patients receiving oral hypoglycemic agents, 23.5% of patients incurred 80% of the all-cause healthcare costs, with these costs being driven by inpatient admissions, complications of diabetes, and chronic diseases. Interventions targeting inpatient admissions and/or complications of diabetes may contribute to the decrease of the diabetes economic burden.     

Weak monotonicity and Bayes–Nash incentive compatibility

An allocation rule is called Bayes–Nash incentive compatible, if there exists a payment rule, such that truthful reports of agents' types form a Bayes–Nash equilibrium in the direct revelation mechanism consisting of the allocation rule and the payment rule. This paper provides a characterization of Bayes–Nash incentive compatible allocation rules in social choice settings where agents have multi-dimensional types, quasi-linear utility functions and interdependent valuations. The characterization is derived by constructing complete directed graphs on agents' type spaces with cost of manipulation as lengths of edges. Weak monotonicity of the allocation rule corresponds to the condition that all 2-cycles in these graphs have non-negative length. For the case that type spaces are convex and the valuation for each outcome is a linear function in the agent's type, we show that weak monotonicity of the allocation rule together with an integrability condition is a necessary and sufficient condition for Bayes–Nash incentive compatibility.     

Profit sharing in unique Nash equilibrium: Characterization in the two-agent case

Two agents jointly operate a decreasing marginal returns technology to produce a private good. We characterize the class of output-sharing rules for which the labor-supply game has a unique Nash equilibrium. It consists of two families: rules of the serial type which protect a small user from the negative externality imposed by a large user, and rules of the reverse serial type, where one agent effectively employs the other agent's labor. Exactly two rules satisfy symmetry; a result in sharp contrast with Moulin and Shenker's characterization of their serial mechanism as the unique cost-sharing rule satisfying the same incentives property [Moulin, H., Shenker, S., 1992. Serial cost sharing. Econometrica 60 (5), 1009–1037]. We also show that the familiar stand-alone test characterizes the class of fixed-path methods under our incentives criterion [Friedman, E.J., 2004. Strong monotonicity in surplus sharing. Econ. Theory 23, 643–658].     

Medical cost reductions associated with the usage of novel oral anticoagulants vs warfarin among atrial fibrillation patients,based on the RE-LY,ROCKET-AF,and ARISTOTLE trials

Abstract

Objective:

The randomized clinical trials, RE-LY, ROCKET-AF, and ARISTOTLE, demonstrate that the novel oral anticoagulants (NOACs) are effective options for stroke prevention among non-valvular atrial fibrillation (AF) patients. This study aimed to evaluate the medical cost reductions associated with the use of individual NOACs instead of warfarin from the US payer perspective.

Methods:

Rates for efficacy and safety clinical events for warfarin were estimated as the weighted averages from the RE-LY, ROCKET-AF and ARISTOTLE trials, and event rates for NOACs were determined by applying trial hazard ratios or relative risk ratios to such weighted averages. Incremental medical costs to a US health payer of an AF patient experiencing a clinical event during 1 year following the event were obtained from published literature and inflation adjusted to 2010 cost levels. Medical costs, excluding drug costs, were evaluated and compared for each NOAC vs warfarin. Sensitivity analyses were conducted to determine the influence of variations in clinical event rates and incremental costs on the medical cost reduction.

Results:

In a patient year, the medical cost reduction associated with NOAC usage instead of warfarin was estimated to be ?$179, ?$89, and ?$485 for dabigatran, rivaroxaban, and apixaban, respectively. When clinical event rates and costs were allowed to vary simultaneously, through a Monte Carlo simulation, the 95% confidence interval of annual medical costs differences ranged between ?$424 and +$71 for dabigatran, ?$301 and +$135 for rivaroxaban, and ?$741 and ?$252 for apixaban, with a negative number indicating a cost reduction. Of the 10,000 Monte-Carlo iterations 92.6%, 79.8%, and 100.0% were associated with a medical cost reduction >$0 for dabigatran, rivaroxaban, and apixaban, respectively.

Conclusions:

Usage of the NOACs, dabigatran, rivaroxaban, and apixaban may be associated with lower medical (excluding drug costs) costs relative to warfarin, with apixaban having the most substantial medical cost reduction.     

Evaluation of the costs and resource use associated with adjuvant chemotherapy for breast cancer in France

Abstract

Objectives:

There is a paucity of recent data on breast cancer costs, particularly on the burden of chemotherapy. The present study was designed to estimate resource use and costs associated with the current standard of care for adjuvant chemotherapy for breast cancer.

Methods:

Costs and resource use were assessed by retrospective analysis of medical records at a single comprehensive cancer care center, Hôpital Tenon, Paris, France. Data were extracted from files of female patients having undergone surgical resection of breast cancer between January–July 2010. Patients were included if they received chemotherapy at the hospital and had medical records available. Patients were followed from the start of adjuvant chemotherapy (including pre-chemotherapy) to the end of treatment. Costs were collected for each resource use item from a societal perspective using standard, published sources and expressed in 2011 Euros (€). Limitations of the analysis included the single-center study design and the use of pre-defined questionnaires on resource use (which may conservatively estimate costs).

Results:

A total of 62 patients were included in the study with a mean age of ～54 years. Most patients had stage II (50.8%) or stage III (40.7%) disease. Anthracycline plus taxane-based chemotherapy regimens were most commonly prescribed (77% of patients). Mean cost of adjuvant chemotherapy was estimated to be ～€15,740 per patient from a societal perspective. The acquisition costs of chemotherapy agents were responsible for 26% of the total, with lost productivity (27%), chemotherapy administration (19%), and adverse events (16%) also contributing substantially.

Conclusions:

Evaluation of costs in patients with non-metastatic breast cancer in France has shown that the costs of adjuvant chemotherapy are substantial. The main components of total cost were the cost of chemotherapy agents, lost productivity, chemotherapy administration, and management and prevention of adverse events.     

Cost effectiveness of posaconazole in the prophylaxis of invasive fungal infections in acute leukaemia patients for the French healthcare system

Abstract

Background:

Acute myeloblastic leukaemia (AML) patients are at high risk of suffering from invasive fungal infections (IFI). Posaconazole demonstrated higher efficacy than standard azole agents (SAA) in the prophylaxis of IFI in this population.

The authors estimated the cost effectiveness of posaconazole versus SAA in France.

Methods:

A decision-tree model was developed to compare posaconazole with SAA with the results of a published clinical trial. Clinical events were modelled with chance nodes reflecting probabilities of IFI, IFI-related death, and death from other causes. Medical resource consumption and costs were obtained from results of the clinical trial and from a dedicated survey on the costs of treating IFI using a retrospective chart review design.

Results:

IFI treatment costs were estimated using medical files from 50 AML patients from six French centres, with a proven and probable IFI, who had been followed-up for 298 days on average. Direct costs directly related to IFI were estimated at €51,033, including extra costs of index hospitalisation, costs of antifungal therapy and additional hospitalisations related to IFI treatment. The model indicated that the healthcare costs for the posaconazole strategy were €5,223 (€2,697 for prophylaxis and €2,526 for IFI management), which was €859 less than the €6,083 in costs with SAA (€469 for prophylaxis and €5614 for IFI management). A sensitivity analysis indicated that there was an 80% probability that prophylaxis using the posaconazole strategy would be superior.

Conclusion:

The findings from this analysis suggest that posaconazole use is a clinically and economically dominant strategy in the prophylaxis of IFI in AML patients, given the usual limits of economic models and the uncertainty of costs estimates.     

The core in an oligopoly market with indivisibility

Summary. This paper studies the core in an oligopoly market with indivisibility. It provides necessary and sufficient conditions for core existence in a general m-buyer n-seller market with indivisibility. When costs are dominated by opportunity costs (i.e., a firm's variable costs are sufficiently small), the core condition can be characterized by the primitive market parameters. In a 3-2 market with opportunity cost, the core is non-empty if and only if the larger seller's opportunity cost is either sufficiently large or sufficiently small. Received: June 9, 1999; revised version: October 22, 1999     

Minimum cost spanning tree problems with indifferent agents

We consider an extension of minimum cost spanning tree (mcst) problems in which some agents do not need to be connected to the source, but might reduce the cost of others to do so. Even if the cost usually cannot be computed in polynomial time, we extend the characterization of the Kar solution (Kar, 2002) for classic mcst problems. It is obtained by adapting the Equal treatment property: if the cost of the edge between two agents changes, their cost shares are affected in the same manner if they have the same demand. If not, their changes are proportional to each other. We obtain a family of weighted Shapley values. Three interesting solutions in that family are characterized using stability, fairness and manipulation-proofness properties.     

Hospital economic impact from hemostatic matrix usage in cardiac surgery

Objective:

Improved health outcomes can result in economic savings for hospitals and payers. While effectiveness of topical hemostatic agents in cardiac surgery has been demonstrated, evaluations of their economic benefit are limited. This study quantifies the cost consequences to hospitals, based on clinical outcomes, from using a flowable hemostatic matrix vs non-flowable topical hemostatic agents in cardiac surgery.

Research design and methods:

Applying clinical outcomes from a prospective randomized clinical trial, a cost consequence framework was utilized to model the economic impact of comparator groups. From that study, clinical outcomes were obtained and analyzed for a flowable hemostatic matrix (FLOSEAL, Baxter Healthcare Corporation) vs non-flowable topical hemostats (SURGICEL Nu-Knit, Ethicon–Johnson &; Johnson; GELFOAM, Pfizer). Costing analyses focused on the following outcomes: complications, blood transfusions, surgical revisions, and operating room (OR) time. Cardiac surgery costs were analyzed and expressed in 2012 US dollars based on available literature searches and US data. Comparator group variability in cost consequences (i.e., cost savings) was calculated based on annualized impact and scenario testing.

Results:

Results suggest that if a flowable hemostatic matrix (rather than a non-flowable hemostat) was utilized exclusively in 600 mixed cardiac surgeries annually, a hospital could improve patient outcomes by a reduction of 33 major complications, 76 minor complications, 54 surgical revisions, 194 transfusions, and 242?h of OR time. These outcomes correspond to a net annualized cost consequence savings of $5.38 million, with complication avoidance as the largest contributor.

Conclusions:

This cost consequence framework and supportive modeling was used to evaluate the hospital economic impact of outcomes resulting from the usage of various hemostatic agents. These analyses support that cost savings can be achieved from routine use of a flowable hemostatic matrix, rather than a non-flowable topical hemostat, in cardiac surgery.     

Adalimumab,etanercept, and infliximab utilization patterns and drug costs among rheumatoid arthritis patients

Abstract

Objectives:

To evaluate the utilization patterns of the anti-tumor necrosis factor (anti-TNF) agents Humira (adalimumab), Enbrel (etanercept), and Remicade (infliximab) in patients with rheumatoid arthritis (RA) and compare medication costs during the first year of treatment. (Humira is a registered trademark of Abbott Laboratories, IL; Enbrel is a registered trademark of Immunex Corporation, CA; and Remicade is a registered trademark of Janssen Biotech, Inc., PA).

Methods:

This retrospective analysis of medical and pharmacy claims included patients who were aged ≥18 years, had ≥2 RA diagnosis codes, and had ≥365 days of persistence with the index anti-TNF. Patients excluded had claims for anti-TNF agents within 6 months before the index date. Refill patterns for adalimumab and etanercept, number of infliximab infusions, time between infusions, and dose per infusion were analyzed for 12 months. Direct anti-TNF medication costs were compared among anti-TNFs for the initial treatment year.

Results:

Infliximab-treated patients (n?=?457) were significantly older than adalimumab- (n?=?337) or etanercept-treated patients (n?=?902). Time between refills was longer than recommended for 28% and 30% of adalimumab and etanercept refill periods, respectively. Potential cumulative time without therapy was 33 days for adalimumab and 43 days for etanercept. Statistically significant differences in mean per-patient anti-TNF medication costs for the first year were reported for adalimumab, etanercept, and infliximab ($14,991, $13,361, and $18,139, respectively; p?<?0.0001); however, a cost assessment using labeled dosing of the anti-TNF agents with optimal treatment compliance yielded comparable annual medication costs.

Limitations:

This analysis only evaluated utilization patterns for selected anti-TNF agents and was not inclusive of other medications that patients may have been using for RA. Absolute patient adherence could not be assessed due to lack of information on how patients were self-administering adalimumab and etanercept or if samples of the agents were made available.

Conclusions:

This study identified gaps in patients’ refills compared with prescriber recommendations. The infliximab-treated group had infusion patterns consistent with prescribing information. Potential clinical and economic implications of dose attenuation with adalimumab and etanercept should be explored further.     

Characterizations of the pivotal mechanism

The pivotal mechanism is strategyproof (demand revealing) in public decision problems where preferences are quasi-linear. Moreover, no agent has an incentive to “free ride” by withdrawing from the committee and consuming whatever decision is taken by the remaining agents. Strategyproofness plus No Free Ride characterize the pivotal mechanism. This mechanism is anonymous and neutral. Yet together Strategyproofness, Anonymity and Neutrality do not characterize it. They will, however, if reasonable lower (or upper) bounds on final utilities are imposed. Our last characterization of the pivotal mechanism uses the No Free Ride axiom and two mild monotonicity properties, but not Strategyproofness.     

Farsightedly stable networks

A set of networks G is pairwise farsightedly stable (i) if all possible farsighted pairwise deviations from any network g G to a network outside G are deterred by the threat of ending worse off or equally well off, (ii) if there exists a farsighted improving path from any network outside the set leading to some network in the set, and (iii) if there is no proper subset of G satisfying conditions (i) and (ii). A non-empty pairwise farsightedly stable set always exists. We provide a full characterization of unique pairwise farsightedly stable sets of networks. Contrary to other pairwise concepts, pairwise farsighted stability yields a Pareto dominant network, if it exists, as the unique outcome. Finally, we study the relationship between pairwise farsighted stability and other concepts such as the largest pairwise consistent set and the von Neumann–Morgenstern pairwise farsightedly stable set.     

Network topology and the efficiency of equilibrium

Different kinds of networks, such as transportation, communication, computer, and supply networks, are susceptible to similar kinds of inefficiencies. These arise when congestion externalities make the cost for each user depend on the other users' choice of routes. If each user chooses the least expensive (e.g., the fastest) route from the users' common point of origin to the common destination, the result may be Pareto inefficient in that an alternative choice of routes would reduce the costs for all users. Braess's paradox represents an extreme kind of inefficiency, in which the equilibrium costs may be reduced by raising the cost curves. As this paper shows, this paradox occurs in an (undirected) two-terminal network if and only if it is not series-parallel. More generally, Pareto inefficient equilibria occur in a network if and only if one of three simple networks is embedded in it.