The effect of outliers on confidence interval procedures for cost-effectiveness ratios

Prednisolone increases neural reactivity to negative socio-emotional stimuli in healthy young men

Exogenous glucocorticoids are known to trigger affective changes, but these are highly variable across individuals. A better understanding of how synthetic glucocorticoids impact the processing of negative emotions in the human brain might help to predict such changes. In the present functional magnetic resonance imaging (fMRI) study, we sought to uncover the slow effects of a synthetic glucocorticoid infusion on the neural response to socio-emotional scenes using a within-participant, double-blind, placebo-controlled design. In two separate sessions, 20 young males were given either an intravenous prednisolone dose (250mg) or placebo in a cross-over, randomized order. Four hours later, they were scanned while viewing drawings of persons in a neutral or negative emotional situation. On the next morning participants provided a blood sample for serum cortisol measurement, which served as a manipulation check. Prednisolone strongly suppressed morning cortisol, and heightened brain reactivity to emotional stimuli in left amygdala, left caudate head, right inferior frontal gyrus, bilateral supplementary motor area, and right somatosensory cortex. Amygdala reactivity was related to lower self-reported fatigue and higher irritability in the prednisolone condition. Moreover, prednisolone blunted inferior frontal and amygdala connectivity with other regions of the emotion-processing neural circuitry. Our results suggest specific brain pathways through which exogenous glucocorticoids may labilize affect.

Sequential Therapies and the Cost-Effectiveness of Treating Metastatic Colon Cancer Patients

BACKGROUND

Technological advances in colon cancer treatment have significantly increased survival outcomes among metastatic patients. With different chemotherapy and biologic regimens administered in first, second, and subsequent lines of treatments, costs and survival outcomes vary considerably. However, there is little evidence on how the type of regime administered in the first line of treatment affects the costs and survival outcomes of the second line of treatment.

OBJECTIVE

To examine how the cost-effectiveness of second-line treatment for elderly metastatic colon cancer patients varies by the type of regimen administered in the first line of treatment.

METHODS

The Surveillance, Epidemiology and End Results (SEER) cancer registry was used, which is linked with the Medicare claims database, to study elderly metastatic patients diagnosed between 2003 and 2009. Average survivals are estimated using the robust nonparametric Kaplan-Meier method. Selection bias was adjusted for using inverse probability weighting and censoring using robust nonparametric methods of estimating the average of total health care costs.

RESULTS

Mean incremental survival was 6.7 months for patients who received second-line treatment (95% CI = 5.7-7.7) compared with those receiving only first-line treatment. However, the mean incremental survival varied between 4 months (95% CI = 0.0-7.3) and 9 months (95% CI = 6.5-11.0) depending on whether fluorouracil with or without leucovorin, irinotecan, oxaliplatin, or other agents were administered in first-line treatment. The mean incremental cost associated with receipt of second-line treatment was $60,231 (95% CI = 52,461-64,198) but ranged between $55,368 (95% CI = 48,294-61,290) and $71,211 (95% CI = 43,168-99,667), depending on the type of regimen administered in the first-line treatment. Combining survival benefits and costs, the incremental cost-effectiveness ratios per life-year gained associated with the receipt of second-line treatment were $97,368 (95% CI = 80,415-117,965); $110,621 (95% CI = 89,560-133,961); $130,689 (95% CI = 101,459-171,918); and $247,951 (95% CI = 112,629808,976) when irinotican, fluorouracil/leucovorin, oxaliplatin, and "other" combinations were, respectively, administered in first-line treatment. In addition, the results varied depending on which statistical method was used.

CONCLUSIONS

When therapies are administered in a sequential manner, the cost-effectiveness of the second line of therapy depends on what was administered in the first line of therapy.

DISCLOSURES

Bayer Healthcare Pharmaceuticals provided funding for this project. Onukwugha has received research funding from Bayer and Amgen and has a consultant/advisory relationship with Jansen Analytics at Johnson & Johnson. Seal was formerly an employee of Bayer and holds stock in Bayer. Mullins has research funding sponsored by Bayer and Pfizer and has a consultant/advisory relationship with Bayer, Amgen, BMS, Genentech, GSK, Novartis, NovoNordisk, and Pfizer. Woldemichael and Nader report no conflicts of interest. All authors contributed to the concept and design of this study. Onukwugha, Seal, and Mullins collected the data, with assistance from Woldemichael and Hanna, while Woldemichael interpreted the data, assisted by the other authors. The manuscript was written primarily by Woldemichael, with assistance from the other authors, and revised by Seal, Hanna, and Mullins, with assistance from Woldemichael and Onukwugha.

An economic evaluation of a self-care intervention in persons with heart failure and diabetes

BACKGROUND

Persons with concomitant heart failure (HF) and diabetes mellitus constitute a growing population whose quality of life is encumbered with worse clinical outcomes as well as high health resource use (HRU) and costs.

METHODS AND RESULTS

Extensive data on HRU and costs were collected as part of a prospective cost-effectiveness analysis of a self-care intervention to improve outcomes in persons with both HF and diabetes. HRU costs were assigned from a Medicare reimbursement perspective. Patients (n = 134) randomized to the self-care intervention and those receiving usual care/attention control were followed for 6 months, revealing significant differences in the number of hospitalization days and associated costs between groups. The mean number of inpatient days was 3 with bootstrapped bias-corrected (BCa) confidence intervals (CIs) of 1.8-4.4 d for the intervention group and 7.3 d (BCa CI 4.1-10.9 d) in the control group: P = .044. Total direct HRU costs per participant were an estimated $9,065 (BCa CI $6,496-$11,936) in the intervention and $16,712 (BCa CI 8,200-$26,621) in the control group, for a mean difference of -$7,647 (BCa CI -$17,588 to $809; P = .21) in favor of the intervention, including intervention costs estimated to be $130.67 per patient.

CONCLUSIONS

The self-care intervention demonstrated dominance in lowering costs without sacrificing quality-adjusted life-years.

Impact of alternative approaches to assess outlying and influential observations on health care costs

The distributions of medical costs are often skewed to the right because small numbers of patients use large amounts of health care resources. Using data from a study of colon cancer costs, we show, by example, the impact and magnitude of outliers and influential observations on health care costs and compared the effects of statistical costing methods for addressing the disproportionate influence of outliers and influential observations. We used data from a retrospective cohort study of 3,842 elderly veterans with colon cancer who were enrolled in and used health care from, both the Department of Veterans Affairs and Medicare in 1999–2004. After calculating the average colon cancer episode cost and distribution for the full cohort, we used box-plot methods, Winsorization, DFBETAs, and Cook's distance to identify and assess or adjust the outlying and/or influential observations. The number of observations identified as outlying and/or influential ranged from 13 when the predicted DFBETA measurement was greater than 0.15 and the observation was a qualified box-plot outlier to 384 cases using the Winsorization method at the 5th and 95th percentiles. Average costs of colon cancer episodes using these methods were similar. The method of choice from the results of this particular analysis can be conditionally based on whether the purpose is to control only for influential observations or to simultaneously control for outliers and influential observations. Understanding how estimates could change with each approach is important in assessing the impact of a particular method on the results.

The Impact of Outliers on Net-Benefit Regression Model in Cost-Effectiveness Analysis

Ordinary least square (OLS) in regression has been widely used to analyze patient-level data in cost-effectiveness analysis (CEA). However, the estimates, inference and decision making in the economic evaluation based on OLS estimation may be biased by the presence of outliers. Instead, robust estimation can remain unaffected and provide result which is resistant to outliers. The objective of this study is to explore the impact of outliers on net-benefit regression (NBR) in CEA using OLS and to propose a potential solution by using robust estimations, i.e. Huber M-estimation, Hampel M-estimation, Tukey's bisquare M-estimation, MM-estimation and least trimming square estimation. Simulations under different outlier-generating scenarios and an empirical example were used to obtain the regression estimates of NBR by OLS and five robust estimations. Empirical size and empirical power of both OLS and robust estimations were then compared in the context of hypothesis testing.

Simulations showed that the five robust approaches compared with OLS estimation led to lower empirical sizes and achieved higher empirical powers in testing cost-effectiveness. Using real example of antiplatelet therapy, the estimated incremental net-benefit by OLS estimation was lower than those by robust approaches because of outliers in cost data. Robust estimations demonstrated higher probability of cost-effectiveness compared to OLS estimation. The presence of outliers can bias the results of NBR and its interpretations. It is recommended that the use of robust estimation in NBR can be an appropriate method to avoid such biased decision making.

Nicotine dependence and cost-effectiveness of individualized support for smoking cessation: evidence from practice at a worksite in Japan

Given the lack of economic studies evaluating the outcomes of smoking cessation programs from the viewpoint of program sponsors, we conducted a case study to provide relevant information for worksites. The present study was carried out between 2006 and 2008 at a manufacturing factory in the Toyama Prefecture of Japan and included subjects who voluntarily entered a smoking cessation program. The program included face-to-face counselling followed by weekly contact to provide encouragement over six months using e-mail or inter-office mail. Nicotine patches were available if required. All 151 participants stopped smoking immediately. Over the 24-month study period, self-report showed 49.7% abstained continuously from smoking. The rate of 24-month consecutive abstinence was higher in participants with lower Fagerström Test scores for Nicotine Dependence at baseline than in those with higher scores (63.6% for 0–2 points vs. 46.5% for 3–6 points vs. 43.8% for 7–10 points; chi-square test p = 0.19). A logistic regression model showed a significant linear trend for the association between the score and abstinence status after adjustment for possible confounding factors (p = 0.03). The crude incremental cost for one individual to successfully quit smoking due to the support program was ¥46,379 (i.e., ¥100 = $1.28, £0.83, or €1.03 at foreign exchange rates). The corresponding costs for the three categories of the Fagerström Test score for Nicotine Dependence were ¥31,953, ¥47,450 and ¥64,956, respectively. When a sensitivity analysis was conducted based on the 95% confidence interval of the success rate, the variance in the corresponding costs was ¥25,514–45,034 for 0–2 points, ¥38,344–61,824 for 3–6 points, and ¥45,698–108,260 for 7–10 points. The degree of nicotine dependence may therefore be an important determinant of the cost-effectiveness of smoking cessation programs.

Using propensity scores to estimate the cost-effectiveness of medical therapies

The cost-effectiveness ratio is a popular statistic that is used by policy makers to decide which programs are cost-effective in the public health sector. Recently, the net monetary benefit has been proposed as an alternative statistical summary measure to overcome the limitations associated with the cost-effectiveness ratio. Research on using the net monetary benefit to assess the cost-effectiveness of therapies in non-randomized studies has yet to be done. Propensity scores are useful in estimating adjusted effectiveness of programs that have non-randomized or quasi-experimental designs. This article introduces the use of propensity score adjustment in cost-effectiveness analyses to estimate net monetary benefits for non-randomized studies. The uncertainty associated with the net monetary benefit estimate is evaluated using cost-effectiveness acceptability curves. Our method is illustrated by applying it to SEER-Medicare data for muscle invasive bladder cancer to determine the most cost-effective treatment protocol.

A propensity score approach to estimating the cost-effectiveness of medical therapies from observational data

Health summary measures are commonly used by policy makers to help make decisions on the allocation of societal resources for competing medical treatments. The net monetary benefit is a health summary measure that overcomes the statistical limitations of a popular measure namely, the cost-effectiveness ratio. We introduce a linear model framework to estimate propensity score adjusted net monetary benefit. This method provides less biased estimates in the presence of significant differences in baseline measures and demographic characteristics between treatment groups in quasi-randomized or observational studies. Simulation studies were conducted to better understand the utility of propensity score adjusted estimates of net monetary benefits when important covariates are unobserved. The results indicated that the propensity score adjusted net monetary benefit provides a robust measure of cost-effectiveness in the presence of hidden bias. The methods are illustrated using data from SEER-Medicare for the treatment of bladder cancer.

Cost-effectiveness of dual-chamber pacing compared with ventricular pacing for sinus node dysfunction

BACKGROUND

Compared with single-chamber ventricular pacing, dual-chamber pacing can reduce adverse events and, as a result, improve quality of life in patients paced for sick sinus syndrome. It is not clear, however, how these benefits compare with the increased cost of dual-chamber pacemakers.

METHODS AND RESULTS

We used 4-year data from a 2010-patient, randomized trial to estimate the incremental cost-effectiveness of dual-chamber pacing compared with ventricular pacing and then projected these findings over the patients' lifetimes by using a Markov model that was calibrated to the first 5 years of in-trial data. To assess the stability of the findings, we performed 1000 bootstrap analyses and multiple sensitivity analyses. During the first 4 years of the trial, dual-chamber pacemakers increased quality-adjusted life expectancy by 0.013 year per subject at an incremental cost-effectiveness ratio of 53,000 dollars per quality-adjusted year of life gained. Over a lifetime, dual-chamber pacing was projected to increase quality-adjusted life expectancy by 0.14 year with an incremental cost-effectiveness ratio of approximately 6800 dollars per quality-adjusted year of life gained. In bootstrap analyses, dual-chamber pacing was cost-effective in 91.9% of simulations at a threshold of 50,000 dollars per quality-adjusted year of life and in 93.2% of simulations at a threshold of 100,000 dollars. Its cost-effectiveness ratio was also below this threshold in numerous sensitivity analyses that varied key estimates.

CONCLUSIONS

For patients with sick sinus syndrome requiring pacing, dual-chamber pacing increases quality-adjusted life expectancy at a cost that is generally considered acceptable.