Juan Marcos Gonzalez

Statistical Methods for the Analysis of Discrete Choice Experiments: A Report of the ISPOR Conjoint Analysis Good Research Practices Task Force

Conjoint analysis is a stated-preference survey method that can be used to elicit responses that reveal preferences, priorities, and the relative importance of individual features associated with health care interventions or services. Conjoint analysis methods, particularly discrete choice experiments (DCEs), have been increasingly used to quantify preferences of patients, caregivers, physicians, and other stakeholders. Recent consensus-based guidance on good research practices, including two recent task force reports from the International Society for Pharmacoeconomics and Outcomes Research, has aided in improving the quality of conjoint analyses and DCEs in outcomes research. Nevertheless, uncertainty regarding good research practices for the statistical analysis of data from DCEs persists. There are multiple methods for analyzing DCE data. Understanding the characteristics and appropriate use of different analysis methods is critical to conducting a well-designed DCE study. This report will assist researchers in evaluating and selecting among alternative approaches to conducting statistical analysis of DCE data. We first present a simplistic DCE example and a simple method for using the resulting data. We then present a pedagogical example of a DCE and one of the most common approaches to analyzing data from such a question format-conditional logit. We then describe some common alternative methods for analyzing these data and the strengths and weaknesses of each alternative. We present the ESTIMATE checklist, which includes a list of questions to consider when justifying the choice of analysis method, describing the analysis, and interpreting the results.

Effect of pill burden on dosing preferences, willingness to pay, and likely adherence among patients with type 2 diabetes

Purpose To quantify willingness-to-pay (WTP) for reducing pill burden and dosing frequency among patients with type 2 diabetes mellitus (T2DM), and to examine the effect of dosing frequency and pill burden on likely medication adherence. Patients and methods Participants were US adults with T2DM on oral antihyperglycemic therapy. Each patient completed an online discrete-choice experiment (DCE) with eight choice questions, each including a pair of hypothetical medication profiles. Each profile was defined by reduction in average glucose (AG), daily dosing, chance of mild-to-moderate stomach problems, frequency of hypoglycemia, weight change, incremental risk of congestive heart failure (CHF), and cost. Patients were asked to rate their likely adherence to the profiles presented in each question. Choice questions were based on a predetermined experimental design. Choice data were analyzed using random-parameters logit. Likely treatment adherence was analyzed using a Heckman two-stage model. Results Of the 1,114 patients who completed the survey, 90 had lower dosing burden (<5 pills/day taken once/day or as needed) for all medications, and 1,024 had higher dosing burden (≥5 pills/day or more than once/day). Reduction in AG was valued most highly by patients. Hypoglycemia, chance of mild-to-moderate stomach problems, weight change, incremental risk of CHF, and daily dosing were less valued. Patients with higher current dosing burden had lower WTP for more convenient dosing schedules than patients with lower current dosing burden. Changes in dosing and cost impacted likely adherence. The magnitude of the impact of dosing on likely adherence was higher for patients with lower current dosing burden than for patients with higher current dosing burden. Conclusion Patients with T2DM were willing to pay for improvements in efficacy, side effects, and dosing. Patients’ WTP for more convenient dosing depended on current dosing burden, as did the effect of these attributes on likely adherence.

A joint estimation method to combine dichotomous choice CVM models with count data TCM models corrected for truncation and endogenous stratification.

We update the joint estimation of revealed and stated preference data of previously published research to allow for joint estimation of the Travel Cost Method (TCM) portion using count data models. The TCM estimation also corrects for truncation and endogenous stratification as well as overdispersion. The joint estimation allows for testing consistency of behavior between revealed and stated preference data rather than imposing it. We find little gain in estimation efficiency, but our joint estimation might make a significant improvement in estimation efficiency when the contingent valuation scenarios involve major changes in site quality not reflected in the TCM data.

The value to patients of reducing lesion severity in plaque psoriasis

Abstract Plaque psoriasis is associated with significant psychosocial, quality-of-life, and economic burden. The objective of this study was to quantify the value to patients of reducing the severity and size of plaque psoriasis lesions. Subjects included individuals with a self-reported diagnosis of plaque psoriasis from a nationally representative US household panel. Subjects completed a web-based conjoint analysis survey and chose between hypothetical treatments in a series of questions. Each alternative was defined by lesion severity, percentage of body surface area (BSA) covered by lesions, type of treatment, injection discomfort or pain (if treatment included injections), risk of serious lung infection, and monthly out-of-pocket cost. 28,200 panelists were invited to participate. 18,330 responded, 503 qualified, and 419 completed the survey. Mean age was 54.5 years and 52% were female. 64% (35%) of patients reported psoriasis severity as mild or mild to moderate (moderate to very severe). Patients were willing to pay

Patients' Willingness to Trade Off Between the Duration and Frequency of Rheumatoid Arthritis Treatments

486.73 out-of-pocket per month to eliminate severe lesions covering 25% BSA on the arms and legs and

Patient preferences for reducing toxicities of treatments for gastrointestinal stromal tumor (GIST)

444.80 out-of-pocket per month to eliminate moderate lesions covering 4% BSA on the face. Individuals with plaque psoriasis are willing to pay substantial amounts to reduce lesion severity and percentage of BSA covered by lesions.

Healthy-days time equivalents for outcomes of acute rotavirus infections

Biologic treatments for rheumatoid arthritis (RA) vary widely in both the time required to administer treatment and treatment frequency. This study aimed to quantify the rate at which RA patients are willing to trade off between the time required to administer treatment (duration) and treatment frequency.

Patient preferences for treatments to delay bone metastases.

Purpose: To quantify gastrointestinal stromal tumor (GIST) patients’ preferences for reducing treatment toxicities and the likely effect of toxicities on patients’ stated adherence. Methods: English-speaking members of the Life Raft Group, a GIST patient advocacy and research organization, aged 18 years and older, completed a web-enabled survey including a series of treatment-choice questions, each presenting a pair of hypothetical GIST medication toxicity profiles. Each profile was defined by common or concerning toxicities verified via pretest interviews including: severity of edema, diarrhea, nausea, fatigue, rash, hand-foot syndrome, and heart failure; and risk of serious infection. Each subject answered 13 choice-format questions based on a predetermined experimental design with known statistical properties. Subjects were asked to rate the likelihood that they would miss or skip doses of medications with different toxicity profiles. Random-parameters logit was used to estimate a relative preference weight for each level of toxicity. Results: 173 subjects completed the survey. Over the ranges of toxicity levels included in the study, heart failure was the most important toxicity. Edema was the least important. For all toxicities, reducing severity from severe to moderate was more important to subjects than reducing severity from moderate to mild. Reducing heart failure from moderate to mild and diarrhea from severe to moderate had the largest effects on subjects’ evaluation of adherence. Conclusions: All toxicities included in the study are important to patients. Treating or reducing severe toxicities is much more important to patients than treating or reducing moderate toxicities. Focused reductions of certain toxicities may improve treatment adherence.

What are people willing to pay for whole-genome sequencing information, and who decides what they receive?:

Rotavirus is the most common cause of severe gastroenteritis in infants and young children worldwide. Health-state utility measures used in economic evaluations of rotavirus vaccines do not reflect differences between mild and severe symptoms of rotavirus gastroenteritis and, therefore, do not adequately capture preferences for non-fatal outcomes associated with rotavirus common in industrialized countries. This paper describes the development and results of a survey specifically designed to develop quality-adjusted time equivalents for rotavirus gastroenteritis among a sample of parents with young children in the United States as an alternative to conventional QALY measures in assessing cost-effectiveness.

Comparing preferences for outcomes of psoriasis treatments among patients and dermatologists in the U.K.: results from a discrete-choice experiment.

Most patients with advanced prostate cancer (PCa) develop bone metastases (BM) and present with bone complications like fracture. Bone‐targeted agents that prevent metastasis‐induced bone complications can cause adverse events. Understanding how patients view treatment options may optimize care. This study aimed to quantify how PCa patients value a hypothetical treatment that delays BM but can cause osteonecrosis of the jaw (ONJ). The study also assessed the value patients place on avoiding metastasis‐induced bone complications versus increased survival.