Joel Tsevat

Model Transparency and Validation A Report of the ISPOR-SMDM Modeling Good Research Practices Task Force–7

Trust and confidence are critical to the success of health care models. There are two main methods for achieving this: transparency (people can see how the model is built) and validation (how well it reproduces reality). This report describes recommendations for achieving transparency and validation, developed by a task force appointed by the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) and the Society for Medical Decision Making (SMDM). Recommendations were developed iteratively by the authors. A nontechnical description should be made available to anyone—including model type and intended applications; funding sources; structure; inputs, outputs, other components that determine function, and their relationships; data sources; validation methods and results; and limitations. Technical documentation, written in sufficient detail to enable a reader with necessary expertise to evaluate the model and potentially reproduce it, should be made available openly or under agreements that protect intellectual property, at the discretion of the modelers. Validation involves face validity (wherein experts evaluate model structure, data sources, assumptions, and results), verification or internal validity (check accuracy of coding), cross validity (comparison of results with other models analyzing same problem), external validity (comparing model results to real-world results), and predictive validity (comparing model results with prospectively observed events). The last two are the strongest form of validation. Each section of this paper contains a number of recommendations that were iterated among the authors, as well as the wider modeling task force jointly set up by the International Society for Pharmacoeconomics and Outcomes Research and the Society for Medical Decision Making.

Spirituality and Religion in Patients with HIV/AIDS

BackgroundSpirituality and religion are often central issues for patients dealing with chronic illness. The purpose of this study is to characterize spirituality/religion in a large and diverse sample of patients with HIV/AIDS by using several measures of spirituality/religion, to examine associations between spirituality/religion and a number of demographic, clinical, and psychosocial variables, and to assess changes in levels of spirituality over 12 to 18 months.MethodsWe interviewed 450 patients from 4 clinical sites. Spirituality/religion was assessed by using 8 measures: the Functional Assessment of Chronic Illness Therapy—Spirituality-Expanded scale (meaning/peace, faith, and overall spirituality); the Duke Religion Index (organized and nonorganized religious activities, and intrinsic religiosity); and the Brief RCOPE scale (positive and negative religious coping). Covariates included demographics and clinical characteristics, HIV symptoms, health status, social support, self-esteem, optimism, and depressive symptoms.ResultsThe patients’ mean (SD) age was 43.3 (8.4) years; 387 (86%) were male; 246 (55%) were minorities; and 358 (80%) indicated a specific religious preference. Ninety-five (23%) participants attended religious services weekly, and 143 (32%) engaged in prayer or meditation at last daily. Three hundred thirty-nine (75%) patients said that their illness had strengthened their faith at least a little, and patients used positive religious coping strategies (e.g., sought God’s love and care) more often than negative ones (e.g., wondered whether God has abandoned me; P<.0001). In 8 multivariable models, factors associated with most facets of spirituality/religion included ethnic and racial minority status, greater optimism, less alcohol use, having a religion, greater self-esteem, greater life satisfaction, and lower overall functioning (R2=.16 to .74). Mean levels of spirituality did not change significantly over 12 to 18 months.ConclusionsMost patients with HIV/AIDS belonged to an organized religion and use their religion to cope with their illness. Patients with greater optimism, greater self-esteem, greater life satisfaction, minorities, and patients who drink less alcohol tend to be both more spiritual and religious. Spirituality levels remain stable over 12 to 18 months.

Impact of morbid obesity on medical expenditures in adults.

CONTEXT:Morbid obesity (body mass index (BMI) ≥40 kg/m2) is associated with substantially increased morbidity and mortality from chronic health conditions and with poorer health-related quality of life; however, less is known about the impact of morbid obesity on healthcare expenditures.OBJECTIVE:To examine the impact of morbid obesity on healthcare expenditures using a nationally representative sample of US adults.DESIGN, SETTING, AND PARTICIPANTS:We performed a cross-sectional analysis of 16 262 adults from the 2000 Medical Expenditure Panel Survey, a nationally representative survey of the noninstitutionalized civilian population of the United States. Per capita healthcare expenditures were calculated for National Institutes of Health BMI categories, based on self-reported height and weight, using a two-part, multivariable model adjusted for age, gender, race, income, education level, type of health insurance, marital status, and smoking status.MAIN OUTCOME MEASURES:Odds of incurring any healthcare expenditure and per capita healthcare expenditures associated with morbid obesity in 2000.RESULTS:When compared with normal-weight adults, the odds of incurring any healthcare expenditure in 2000 were two-fold greater among adults with morbid obesity. Per capita healthcare expenditures for morbidly obese adults were 81% (95% confidence interval (CI): 48–121%) greater than normal-weight adults, 65% (95% CI: 37–110%) greater than overweight adults, and 47% (95% CI: 11–96%) greater than adults with class I obesity. Excess costs among morbidly obese adults resulted from greater expenditures for office-based visits, outpatient hospital care, in-patient care, and prescription drugs. Aggregate US healthcare expenditures associated with excess body weight among morbidly obese US adults exceeded

Expected gains in life expectancy from various coronary heart disease risk factor modifications.

11 billion in 2000.CONCLUSIONS:The economic burden of morbid obesity among US adults is substantial. Further research is needed to identify interventions to reduce the incidence and prevalence of morbid obesity and improve the health and economic outcomes of morbidly obese adults.

Stability of Time-tradeoff Utilities in Survivors of Myocardial Infarction

BackgroundDespite much evidence that modifying risk factors for coronary heart disease can decrease morbidity and mortality, little is known about the impact of risk-factor modification on life expectancy. Methods and ResultsWe used the Coronary Heart Disease Policy Model, a state-transition computer simulation of the US population, to forecast potential gains in life expectancy firom risk-factor modification for the cohort of Americans turning age 35 in 1990. Among 35-year-old men, we projected that the population-wide increase in life expectancy would be about 1.1 years from strict blood pressure control, 0.8 years from smoking cessation, 0.7 years from reduction of serum cholesterol to 200 mg/dl, and about 0.6 years from weight loss to ideal body weight. For women, reducing cholesterol to 200 mg/dl would have the greatest estimated impact-a gain of 0.8 years whereas smoking cessation, blood pressure control, or weight loss would yield populationwide gains of 0.7, 0.4, and 0.4 years, respectively. Gains for 35-year-old individuals having a given risk factor are greater. We estimate that, on average, male smokers would gain 2.3 years from quitting smoking; males with hypertension would gain 1.1-5.3 years from reducing their diastolic blood pressure to 88 mm Hg; men with serum cholesterol levels exceeding 200 mg/dl would gain 0.5-4.2 years from lowering their serum cholesterol level to 200 mg/dl; and overweight men would gain an average of 0.7-1.7 years from achieving ideal body weight. Corresponding projected gains for at-risk women are 2.8 years from quitting smoking, 0.9-5.7 years from lowering blood pressure, 0.4-6.3 years from decreasing serum cholesterol, and 0.5-1.1 years from losing weight. Eliminating coronary heart disease mortality is estimated to extend the average life expectancy of a 35-year-old man by 3.1 years and a 35-year-old woman by 3.3 years. ConclusionsPopulation-wide gains in life expectancy from single risk-factor modifications are modest, but gains to individuals at risk can be more substantial.

Willingness to Pay for a Quality-Adjusted Life Year: Implications for Societal Health Care Resource Allocation:

To investigate whether time-tradeoff utilities of survivors of myocardial infarction change over time and whether changes in utilities correlate with changes in functional status, the authors conducted serial interviews using a time tradeoff and three measures of functional status in a cohort of 67 patients who had recently had myocardial infarction. The patients were also asked to rate their overall health on a rating scale and were asked about chest pain, exercise status, and employment status. Each patient was interviewed two to five times over one and a half years. The mean (95% Cl) time-tradeoff score for all patients was 0.88 (0.84, 0.93). Over a mean interval of 8.4 months, 28 (42%) patients changed Karnofsky scores, 28 (42%) changed Specific Activity Scale classes, and 11 (16%) changed New York Heart Association classes, with most changes representing improvements in functional status. Scores on the rating scale improved by a mean (95% Cl) of 0.06 [(0.03, 0.10); p < 0.002], but scores on the time tradeoff remained stable, with a mean (95% Cl) change of 0.03 [(-0.02, 0.08); p = NS]. Changes in time-tradeoff scores did not correlate with changes in Specific Activity Scale classes (Kendalls τ = 0.21), New York Heart Association classes (τ = -0.02), or Karnofsky scores (τ = 0.14); with changes on the verbal rating scale (R = 0.20); with changes in chest pain status (τ = -0.05), exercise status (τ = 0.11), or employment status (τ = 0.11); or with interim hospitalizations (τ = 0.05). The authors conclude that, in this relatively stable group of survivors of myocardial infarction, time-tradeoff utilities remained stable, and that changes in time-tradeoff utilities did not correlate with changes in function. Key words: functional status; quality of life; utility; patient preferences; myocardial infarction. (Med Decis Making 1993;13:161-165)

Religious Coping and Physiological, Psychological, Social, and Spiritual Outcomes in Patients with HIV/AIDS: Cross-sectional and Longitudinal Findings

Background . Health-state preferences can be combined with willingness-to-pay (WTP) data to calculate WTP per quality-adjusted life year (QALY). The WTP/QALY ratios provide insight into societal valuations of expenditures for medical interventions. Methods . The authors measured preferences for current health in 3 patient populations (N = 391) using standard gamble, time trade-off, visual analog scale, and WTP, then they calculated WTP/QALY ratios. The ratios were compared with several proposed cost/QALY cost-effectiveness ratio thresholds, the value-of-life literature, and with WTP/QALY ratios derived from published preference research. Results . Mean WTP/QALY ratios ranged from

Model transparency and validation: a report of the ISPOR-SMDM Modeling Good Research Practices Task Force--7

12,500 to

Cost-effectiveness of a smoking cessation program after myocardial infarction

32,200 (2003

Predicting functional status outcomes in hospitalized patients aged 80 years and older

US). All values were below most published cost-effectiveness ratio thresholds, below the ratio from a prototypic medical treatment covered by Medicare (i.e., renal dialysis), and below ratios from the value-of-life literature. The WTP/QALY ratios were similar to those calculated from published preference data for patients with symptomatic meno-pause, dentofacial deformities, asthma, or dermatologic disorders. Conclusions . WTP/QALY ratios calculated using preference data collected from diverse populations are lower than most proposed thresholds for determining what is “cost-effective.” Current proposed cost-effectiveness ratio thresholds may overestimate the willingness of society to pay for medical interventions.