New econometric models for longitudinal count data with an excess of zeros : two applications in health economics

The purpose of this doctoral thesis is to provide new econometric models to analyze longitudinal count data characterized by a high proportion of zeros in the data. Previous econometric studies have dealt with many characteristics such as the discrete and longitudinal aspects of the dependent count variable or the presence of covariates and unobserved individual heterogeneity. However, none have taken into account the issues associated with an excess of zeros in a longitudinal framework. While it is well known in the univariate case that when an excess of zeros is significant, the mean has to be corrected to take into account this feature of the data, this issue has often been ignored in the longitudinal case. An excess of zeros in the data may lead to important modeling issues associated with the analysis of longitudinal count data. Two new econometric models are presented to address the six following characteristics: (1) count outcome, (2) a limited number of repeated measurements, (3) presence of covariates, (4) unobserved heterogeneity, (5) presence of correlation due to the repeated nature of the data and (6) an excess of zeros. The first model, a Quadrivariate Negative Binomial Hurdle model, was developed to analyze the number of doctor visits made by a panel of more than 4,000 German followed over 4 years. In the second example, a Quadrivariate Negative Binomial Zero-Inflated model was used to analyze an unpublished subset of a longitudinal clinical trial in which the treatments were very effective in reducing the number of occurrences of one variable collected over time in this trial. These two new models were nested to the Quadrivariate Negative Binomial model, allowing us to test for an excess of zeros. The main result is that the excess of zeros was significant in our two examples and assuming that only one process generates the data is incorrect. As such, the Multivariate Negative Binomial Hurdle and Zero-Inflated models are superior than standard Univariate Negative Binomial model, Quadrivariate Negative Binomial model and Generalized Estimating Equations model. These new models performed well in predicting the mean counts and the mean proportion of zeros in the data at each time period. This thesis demonstrated that caution should be taken in analyzing longitudinal count data in the presence of a high proportion of zeros in the data and correlation over time. Models ignoring these features may yield inconsistent estimates

Health utilities index mark 3 scores for major chronic conditions : population norms for Canada based on the 2013-2014 Canadian Community Health Survey

Background: Utility scores are frequently used as preference weights when estimating quality-adjusted life-years within cost-utility analyses or health-adjusted life expectancies. Though previous Canadian estimates for specific chronic conditions have been produced, these may no longer reflect current patient populations. Data and methods: Data from the 2013-2014 Canadian Community Health Survey were used to provide Canadian utility score norms for seventeen chronic conditions. Utility scores were estimated using the Health Utilities Index Mark 3 (HUI3) instrument and were reported as weighted average (95% confidence intervals [95% CI]) values. In addition to age and sex-stratified analyses, results were also stratified according to the number of reported chronic conditions (i.e., “none” to “≥5”). All results were weighted using sampling and bootstrapped weights provided by Statistics Canada. Results: Utility scores were estimated for 123,654 (97.2%) respondents (weighted frequency = 29,337,370 [97.7%]). Of the chronic conditions that were examined, “Asthma” had the least detrimental effect (weighted average utility score = 0.803 [95%CI 0.795 – 0.811]) on respondents’ utility scores and “Alzheimer’s disease or any other dementia” had the worst (weighted average utility score = 0.374 [95%CI 0.323 – 0.426]). Respondents who reported suffering from no chronic conditions had, on average, the highest utility scores (weighted average utility score = 0.928 [95%CI 0.926 – 0.930]); estimates dropped as a function of the number of reported chronic conditions. Interpretation: Utility score differed between various chronic conditions and as a function of the number of reported chronic conditions. Results also highlight several differences with previously published Canadian utility norms

How Does the Canadian General Public Rate Moderate Alzheimer's Disease?

Objectives. The objectives of this study were to elicit health utility scores for moderate Alzheimer's disease (AD) using members of the general public. Methods. Five-hundred Canadians were chosen randomly to participate in a telephone interview. The EQ-5D was administered to estimate the health utility score for respondents' current health status (i.e., no AD) and for a hypothetical moderate AD health state. Regression analyses were conducted to explain the perceived utility decrement associated with AD. Results. The mean age of the respondents was 51 years, 60% were female, and 42% knew someone with AD. Respondents' mean EQ-5D scores for their current health status and a hypothetical moderate AD were 0.873 (SD: 0.138) and 0.638 (SD: 0.194), respectively (P < 0.001). Age, gender, and education were significant factors explaining this decrement in utility. Conclusion. Members of the general public may serve as an alternative to patients and caregivers in the elicitation of health-related quality of life in AD

A Multinational Pharmacoeconomic Evaluation of Acute Major Depressive Disorder (MDD): a Comparison of Cost-Effectiveness Between Venlafaxine, SSRIs and TCAs

AbstractMethodsWe conducted a multinational pharmacoeconomic evaluation comparing the immediate release form of a new class of serotonin norepinephrine reuptake inhibitor (SNRI), venlafaxine IR to the selective serotonin reuptake inhibitors (SSRIs) and the tricyclic antidepressants (TCAs) in the treatment of acute major depressive disorder (MDD) in 10 countries (Germany, Italy, Netherlands, Poland, Spain, Sweden, Switzerland, United Kingdom, United States, and Venezuela). We designed a decision analytic model assessing the acute phase of MDD treatment within a 6-month time horizon. Six decision tree models were customized with country-specific estimates from a clinical management analysis, meta-analytic rates from two published meta-analyses, and a resource valuation of treatment costs representing the inpatient and outpatient settings within each country. The meta-analyses provided the clinical rates of success defined as a 50% reduction in depression scores on the Hamilton Depression Scale (HAM-D) or the Montgomery-Asberg Depression Rating Scale (MADRS). Treatment regimen costs were determined from standard lists, fee schedules, and communication with local health economists in each country. The meta-analytic rates were applied to the decision analytic model to calculate the expected cost and expected outcomes for each antidepressant comparator. Cost-effectiveness was determined using the expected values for both a successful outcome, and a composite measure of outcome termed symptom-free days. A policy analysis was conducted to examine the health system budget impact in each country of increasing the utilization of the most effective antidepressant found in our study.ResultsInitiating treatment of MDD with venlafaxine IR yielded a lower expected cost compared to the SSRIs and TCAs in all countries except Poland in the inpatient setting, and Italy and Poland within the outpatient settings. The weighted average expected cost per patient varied from US$632 (Poland) to US$5647 (US) in the six-month acute phase treatment of MDD. The estimated total budgetary impact for each 1% of venlafaxine utilization, assuming a population of one million MDD patients, ranged from US$1600 (Italy) to US$29,049 (US).ConclusionsWithin the inpatient and outpatient treatment settings, venlafaxine IR was a more cost-effective treatment of MDD compared to the SSRIs and TCAs. Additionally, the results of this investigation indicate that increased utilization of venlafaxine in most settings across Europe and the Americas will have favorable impact on health care payer budgets.ADR, adverse drug reaction; CMA, clinical management analysis; ECT, electroconvulsive therapy; HAM-D, Hamilton Depression Scale; MADRS, Montgomery-Asberg depression rating scale; MDD, major depressive disorder; SFD, symptom-free day; SNRI, serotonin-norepinephrine reuptake inhibitor; SSRI, selective serotonin reuptake inhibitor; TCA, tricyclic antidepressant; WHO, world health organization

Just how much does it cost? A cost study of chronic pain following cardiac surgery

Objective: The study objective was to determine use of pain-related health care resources and associated direct and indirect costs over a two-year period in cardiac surgery patients who developed chronic post-surgical pain (CPSP). Methods: This multicentric observational prospective study recruited patients prior to cardiac surgery; these patients completed research assistant-administered questionnaires on pain and psychological characteristics at 6, 12 and 24 months post-operatively. Patients reporting CPSP also completed a one-month pain care record (PCR) (self-report diary) at each follow-up. Data were analyzed using descriptive statistics, multivariable logistic regression models, and generalized linear models with log link and gamma family adjusting for sociodemographic and pain intensity. Results: Out of 1,247 patients, 18%, 13%, and 9% reported experiencing CPSP at 6, 12, and 24 months, respectively. Between 16% and 28% of CPSP patients reported utilizing health care resources for their pain over the follow-up period. Among all CPSP patients, mean monthly pain-related costs were CAN$207 at 6 months and significantly decreased thereafter. More severe pain and greater levels of pain catastrophizing were the most consistent predictors of health care utilization and costs. Discussion: Health care costs associated with early management of CPSP after cardiac surgery seem attributable to a minority of patients and decrease over time for most of them. Results are novel in that they document for the first time the economic burden of CPSP in this population of patients. Longer follow-up time that would capture severe cases of CPSP as well as examination of costs associated with other surgical populations are warranted. Summary: Economic burden of chronic post-surgical pain may be substantial but few patients utilize resources. Health utilization and costs are associated with pain and psychological characteristics

Evaluation of health outcomes in osteoarthritis patients after total knee replacement: a two-year follow-up

10.1186/1477-7525-8-87Health and Quality of Life Outcomes8

A review of health utilities across conditions common in paediatric and adult populations

<p>Abstract</p> <p>Background</p> <p>Cost-utility analyses are commonly used in economic evaluations of interventions or conditions that have an impact on health-related quality of life. However, evaluating utilities in children presents several challenges since young children may not have the cognitive ability to complete measurement tasks and thus utility values must be estimated by proxy assessors. Another solution is to use utilities derived from an adult population. To better inform the future conduct of cost-utility analyses in paediatric populations, we reviewed the published literature reporting utilities among children and adults across selected conditions common to paediatric and adult populations.</p> <p>Methods</p> <p>An electronic search of Ovid MEDLINE, EMBASE, and the Cochrane Library up to November 2008 was conducted to identify studies presenting utility values derived from the Health Utilities Index (HUI) or EuroQoL-5Dimensions (EQ-5D) questionnaires or using time trade off (TTO) or standard gamble (SG) techniques in children and/or adult populations from randomized controlled trials, comparative or non-comparative observational studies, or cross-sectional studies. The search was targeted to four chronic diseases/conditions common to both children and adults and known to have a negative impact on health-related quality of life (HRQoL).</p> <p>Results</p> <p>After screening 951 citations identified from the literature search, 77 unique studies included in our review evaluated utilities in patients with asthma (n = 25), cancer (n = 23), diabetes mellitus (n = 11), skin diseases (n = 19) or chronic diseases (n = 2), with some studies evaluating multiple conditions. Utility values were estimated using HUI (n = 33), EQ-5D (n = 26), TTO (n = 12), and SG (n = 14), with some studies applying more than one technique to estimate utility values. 21% of studies evaluated utilities in children, of those the majority being in the area of oncology. No utility values for children were reported in skin diseases. Although few studies provided comparative information on utility values between children and adults, results seem to indicate that utilities may be similar in adolescents and young adults with asthma and acne. Differences in results were observed depending on methods and proxies.</p> <p>Conclusions</p> <p>This review highlights the need to conduct future research regarding measurement of utilities in children.</p