Health status versus utilities of patients with end-stage liver disease

Cost-effectiveness analysis of adult living-donor liver transplantation in Japan

AIM

Living-donor liver transplantation (LDLT) is a highly effective life-saving procedure; however, it requires substantial medical resources, and the cost-effectiveness of LDLT versus conservative management (CM) for adult patients with end-stage liver disease (ESLD) remains unclear in Japan.

METHODS

We performed a cost-effectiveness analysis using the Diagnostic Procedure Combination (DPC) data from the nationwide database of the DPC research group. We selected adult patients (18 years or older) who were admitted or discharged between 2010 and 2021 with a diagnosis of ESLD with Child-Pugh class C or B. A decision tree and Markov model were constructed, and all event probabilities were computed in 3-month cycles over a 10-year period. The willingness-to-pay per quality-adjusted life-year (QALY) was set at 5 million Japanese yen (JPY) (49,801 US dollars [USD]) from the perspective of the public health-care payer.

RESULTS

After propensity score matching, we identified 1297 and 111,849 patients in the LDLT and CM groups, respectively. The incremental cost-effectiveness ratio for LDLT versus CM for Child-Pugh classes C and B was 2.08 million JPY/QALY (20,708 USD/QALY) and 5.24 million JPY/QALY (52,153 USD/QALY), respectively. The cost-effectiveness acceptability curves showed the probabilities of being below the willingness-to-pay of 49,801 USD/QALY as 95.4% in class C and 48.5% in class B. Tornado diagrams revealed all variables in class C were below 49,801 USD/QALY while their ranges included or exceeded 49,801 USD/QALY in class B.

CONCLUSIONS

Living-donor liver transplantation for adult patients with Child-Pugh class C was cost-effective compared with CM, whereas LDLT versus CM for class B patients was not cost-effective in Japan.

Comprehensive Health-State Utilities in Contemporary Patients With Cirrhosis

Cost‐effectiveness analysis depends on generalizable health‐state utilities. Unfortunately, the available utilities for cirrhosis are dated, may not reflect contemporary patients, and do not capture the impact of cirrhosis symptoms. We aimed to determine health‐state utilities for cirrhosis, using both the standard gamble (SG) and visual analog scale (VAS). We prospectively enrolled 305 patients. Disease severity (Child‐Pugh [Child] class, Model for End‐Stage Liver Disease with sodium [MELD‐Na] scores), symptom burden (sleep quality, cramps, falls, pruritus), and disability (activities of daily living) were assessed. Multivariable models were constructed to determine independent clinical associations with utility values. The mean age was 57 ± 13 years, 54% were men, 30% had nonalcoholic steatohepatitis, 26% had alcohol‐related cirrhosis, 49% were Child class A, and the median MELD‐Na score was 12 (interquartile range [IQR], 8‐18). VAS displayed a normal distribution with a wider range than SG. The Child‐specific SG‐derived utilities had a median value of 0.85 (IQR, 0.68‐0.98) for Child A, 0.78 (IQR, 0.58‐0.93) for Child B, and 0.78 (IQR, 0.58‐0.93) for Child C. VAS‐derived utilities had a median value of 0.70 (IQR, 0.60‐0.85) for Child A, 0.61 (IQR, 0.50‐0.75) for Child B, and 0.55 (IQR, 0.40‐0.70) for Child C. VAS and SG were weakly correlated (Spearman's rank correlation coefficient, 0.12; 95% confidence interval, 0.006‐0.23). In multivariable models, disability, muscle cramps, and MELD‐Na were significantly associated with SG utilities. More clinical covariates were significantly associated with the VAS utilities, including poor sleep, MELD‐Na, disability, falls, cramps, and ascites. Conclusion: We provide health‐state utilities for contemporary patients with cirrhosis as well as estimates of the independent impact of specific symptoms on each patient’s reported utility.

Utility outcome assessment of pes planus deformity

BACKGROUND

Despite being a common condition, there are no objective measures in the literature to reflect the burden of pes planus on affected individuals. Our primary objective was to evaluate this burden by recruiting a sample from the general population using validated utility outcome measures.

METHODS

Participants were recruited online and filled a questionnaire to help measure the health burden of pes planus. Three recognized utility outcome scores were used to compare the health burden of monocular blindness, binocular blindness, and pes planus. These included the standard gamble (SG), time trade-off (TTO), and visual analogue score (VAS). Paired t test, independent t test, and linear regression were used for statistical analysis.

RESULTS

Ninety-two participants were included in the final analysis. The utility outcome scores (VAS, TTO, SG) for pes planus were 73±17, 0.90±0.08, and 0.88±0.12, respectively. The linear regression analysis showed that age was inversely proportional to the time trade-off. However, race, educational level, and income were not significant predictors of utility outcome score for pes planus.

CONCLUSIONS

This study shows that the perceived burden of living with pes planus is comparable to living with some debilitating conditions. Our participants were willing to sacrifice 3.6 years of life, and have a procedure with a theoretical 12% mortality risk to attain perfect health.

Experiences of Individuals With Liver Cirrhosis: A Qualitative Study

Liver cirrhosis is one of the main causes of mortality and morbidity worldwide. Health-related quality of life in cirrhotic patients is affected by the disease's complications. The purpose of this article was to describe the experiences of individuals with liver cirrhosis during critical illness. The aim was to investigate the disease experiences of liver cirrhosis. The authors conducted a phenomenological qualitative study, using a Colaizzi's seven-step method. Ten participants with liver cirrhosis participated in in-depth interviews. The data from this analysis were transformed into 119 codes, 11 subthemes, and 4 main themes including (1) confronting tension, (2) needs, (3) spirituality, and (4) interaction and effective communication. Findings could be used as a basis for information and emotional and social support interventions, as these can be effective in promoting adjustment to complications of cirrhosis by suitable interventions. Adequate adjustment through adaptation leads to successful completion of treatment and improved quality of life.

The time horizon matters: results of an exploratory study varying the timeframe in time trade-off and standard gamble utility elicitation

INTRODUCTION

The purpose of this study was to examine whether the time horizon of time trade-off (TTO) and standard gamble (SG) utility assessment influences utility scores and discrimination between health states.

METHODS

In two phases, UK general population participants rated three osteoarthritis health states in TTO and SG procedures with two time horizons: (1) 10-year and (2) a time horizon derived from self-reported additional life expectancy (ALE). The two time horizons were compared in terms of mean utilities and discrimination among health states.

RESULTS

In Phase 1, the 10-year tasks were completed by 80 participants, 35 of whom also completed utility assessment with the ALE. In Phase 2, all 101 participants completed procedures with both time horizons. Utility scores tended to be lower with the ALE than the 10-year, a difference that was statistically significant for two health states with SG in Phase 1 (P < 0.05), two health states with TTO in Phase 2 (P < 0.01), and one health state with SG in Phase 2 (P < 0.001). In Phase 1, rates of discrimination between mild and moderate osteoarthritis health states were significantly higher with the ALE than the 10-year (TTO: P = 0.03; SG: P = 0.001). This pattern of discrimination was similar in Phase 2.

DISCUSSION

Results suggest that the time horizon could influence utility scores and discrimination among health states. When designing utility evaluations, researchers should carefully consider the time horizon so that the value of health states is accurately represented in cost-utility models.

Palliative care for patients with end-stage liver disease

Liver disease results in over four million physician visits and over 750,000 hospitalizations per year in the USA. Those with chronic liver disease frequently progress to cirrhosis, end-stage liver disease (ESLD), and death. Patients with ESLD experience numerous complications, including muscle cramps, confusion (hepatic encephalopathy), protein calorie malnutrition, muscle wasting, fluid overload (ascites, edema), bleeding (esophagogastric variceal hemorrhage), infection (spontaneous bacterial peritonitis), fatigue, anxiety, and depression. Despite significant improvements in palliation of these complications, patients still suffer reduced quality of life and must confront the fact that their disease will often inexorably progress to death. Liver transplantation is a valid option in this setting, increasing the duration of survival and palliating many of the symptoms. However, many patients die waiting for an organ or are not candidates for transplantation due to comorbid illness. Others receive a transplant but succumb to complications of the transplant itself. Patients and families must struggle with simultaneously hoping for a cure while facing a life-threatening illness. Ideally, the combination of palliative care with life-sustaining therapy can maximize the patients' quality and quantity of life. If it becomes clear that life-sustaining therapy is no longer an option, these patients are then already in a system to help them with end-of-life care.

Utility values for specific hepatic encephalopathy health states elicited from the general public in the United Kingdom

Background and aims

To elicit utility values for five health states corresponding to increasing severity of hepatic encephalopathy, from members of the general public in the UK. The health states studied were Conn grades 0, 1, 2, 3 and 4.

Methods

Interviewer-administered time trade-off (TTO) and standard gamble (SG) utilities were elicited for the five health states from a random sample of 200 members of the general public in the UK, using health state descriptions validated by clinicians and members of the general public.

Results

Respondents’ mean age was 49.5 years and 49% were female. Mean utilities were 0.962 (TTO) and 0.915 (SG) for Conn grade 0; 0.912 (TTO) and 0.837 (SG) for Conn grade 1; 0.828 (TTO) and 0.683 (SG) for Conn grade 2; 0.691 (TTO) and 0.489 (SG) for Conn grade 3; and 0.429 (TTO) and 0.215 (SG) for Conn grade 4. The TTO and SG values between the five Conn grades were significantly different (p < 0.001). Additionally, the TTO value was significantly higher than the SG value for the corresponding state (p <0.0001).

Conclusion

These findings quantify how different Conn grades and level of response to treatment may impact on the health-related quality of life of patients with hepatic encephalopathy. There were greater preference values for lower levels of disease, with the highest value associated with Conn grade 0. These health state preference values can be used to estimate the outcomes of different interventions for hepatic encephalopathy in terms of quality-adjusted life years.

Comparison of direct-measured and derived short form six dimensions (SF-6D) health preference values among chronic hepatitis B patients

PURPOSE

The short form six dimensions (SF-6D) are derived from the SF-36 Health Survey with the intention that item data of the latter are often converted to a preference value, which was subsequently used in economic evaluations of interventions. The aim was to compare the equivalence and sensitivity of health preference values derived from the SF-36/SF-12 Health Surveys to that measured directly by the SF-6D for chronic hepatitis B (CHB) patients.

METHODS

This was a secondary analysis of the SF-6D and SF-36 data from a baseline sample of 589 patients with CHB infection with different stages of liver diseases. Degree of agreement (equivalence) between direct-measured and derived SF-6D values was determined using spearman correlation and intra-class correlation. Sensitivity and discriminative power of different SF-6D values were compared by standardized effect size and relative efficiency (RE) statistics.

RESULTS

Significant differences in the direct-measured or derived SF-6D preference values were found between CHB groups. Degree of agreement between SF-6D values was satisfactory. Direct-measured SF-6D was the most efficient, followed by SF-12-derived and the SF-36-derived was the least, based on the standardized effect size and the RE statistics. Sensitivity and discriminative power of direct-measured SF-6D were superior to derived SF-6D among people with different CHB health states.

CONCLUSIONS

Although direct-measured and derived SF-6D preference values had satisfactory sensitivity in discriminating between CHB groups, direct-measured SF-6D is the most sensitive and preferable method of obtaining health preference.

Cancer patient and survivor research from the cancer information service research consortium: a preview of three large randomized trials and initial lessons learned

The authors describe 3 large randomized trials from the Cancer Information Service Research Consortium. Three web-based multimedia programs are being tested to help newly diagnosed prostate (Project 1) and breast cancer patients (Project 2) make informed treatment decisions and breast cancer patients prepare for life after treatment (Project 3). Project 3 also tests a telephone callback intervention delivered by a cancer information specialist. All participants receive standard print material specific to each project. Preliminary results from the 2-month follow-up interviews are reported for the initial wave of enrolled participants, most of whom were recruited from the Cancer Information Service (1-800-4-CANCER) telephone information program (Project 1: n =208; Project 2: n =340; Project 3: n =792). Self-reported use of the multimedia program was 51%, 52%, and 67% for Projects 1, 2, and 3, respectively. Self-reported use of the print materials (read all, most, or some) was 90%, 85%, and 83% for Projects 1, 2, and 3, respectively. The callback intervention was completed by 92% of Project 3 participants. Among those using the Cancer Information Service Research Consortium interventions, perceived usefulness and benefit was high, and more than 90% reported that they would recommend them to other cancer patients. The authors present 5 initial lessons learned that may help inform future cancer communications research.

Comparative effectiveness of donation after cardiac death versus donation after brain death liver transplantation: Recognizing who can benefit

Due to organ scarcity and wait-list mortality, transplantation of donation after cardiac death (DCD) livers has increased. However, the group of patients benefiting from DCD liver transplantation is unknown. We studied the comparative effectiveness of DCD versus donation after brain death (DBD) liver transplantation. A Markov model was constructed to compare undergoing DCD transplantation with remaining on the wait-list until death or DBD liver transplantation. Differences in life years, quality-adjusted life years (QALYs), and costs according to candidate Model for End-Stage Liver Disease (MELD) score were considered. A separate model for hepatocellular carcinoma (HCC) patients with and without MELD exception points was constructed. For patients with a MELD score <15, DCD transplantation resulted in greater costs and reduced effectiveness. Patients with a MELD score of 15 to 20 experienced an improvement in effectiveness (0.07 QALYs) with DCD liver transplantation, but the incremental cost-effectiveness ratio (ICER) was >$2,000,000/QALY. Patients with MELD scores of 21 to 30 (0.25 QALYs) and >30 (0.83 QALYs) also benefited from DCD transplantation with ICERs of $478,222/QALY and $120,144/QALY, respectively. Sensitivity analyses demonstrated stable results for MELD scores <15 and >20, but the preferred strategy for the MELD 15 to 20 category was uncertain. DCD transplantation was associated with increased costs and reduced survival for HCC patients with exception points but led to improved survival (0.26 QALYs) at a cost of $392,067/QALY for patients without exception points. In conclusion, DCD liver transplantation results in inferior survival for patients with a MELD score <15 and HCC patients receiving MELD exception points, but provides a survival benefit to patients with a MELD score >20 and to HCC patients without MELD exception points.

Patient decision making about organ quality in liver transplantation

It is challenging to discuss the use of high-risk organs with patients, in part because of the lack of information about how patients view this topic. This study was designed to determine how patients think about organ quality and to test formats for risk communication. Semistructured interviews of 10 patients on the waiting list revealed limited understanding about the spectrum of organ quality and a reluctance to consider anything but the best organs. A computerized quantitative survey was then conducted with an interactive graph to elicit the risk of graft failure that patients would accept. Fifty-eight percent of the 95 wait-listed patients who completed the survey would accept only organs with a risk of graft failure of 25% or less at 3 years, whereas 18% would accept only organs with the lowest risk possible (19% at 3 years). Risk tolerance was increased when the organ quality was presented relative to average organs rather than the best organs and when feedback was provided about the implications for organ availability. More than three-quarters of the patients reported that they wanted an equal or dominant role in organ acceptance decisions. Men tended to prefer lower risk organs (mean acceptable risk = 29%) in comparison with women (mean acceptable risk = 35%, P = 0.04), but risk tolerance was not associated with other demographic or clinical characteristics (eg, the severity of liver disease). In summary, patients want to be involved in decisions about organ quality. Patients' risk tolerance varies widely, and their acceptance of high-risk organs can be facilitated if we present the risks of graft failure with respect to average organs and provide feedback about the implications for organ availability.

Trading years for perfect health: results from the health and retirement study

OBJECTIVE

To evaluate the preferences of an ethnically diverse national sample of older Americans regarding length of life versus health quality.

METHOD

A time trade-off task administered as part of the 2002 wave of the Health and Retirement Study.

RESULTS

Respondents equated 6.86 (SD = 3.46) years of perfect health with 10 years of life in imperfect health. Women and those who ranked their health less favorably were more likely to give up years of life for perfect health. Relative to Whites, Blacks were more willing to live longer in imperfect health. Those of lower levels of education were more likely to prefer 10 years of life in imperfect health.

DISCUSSION

There is wide variability in responses to the time trade-off task that is partially associated with self-rated health, gender, ethnicity, and education.

Does cirrhosis affect quality of life in hepatitis C virus-infected patients?

BACKGROUND

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and is associated with impairments in health-related quality of life.

AIMS

To evaluate quality of life (QOL) in cirrhotic (compensated and decompensated) and non-cirrhotic patients with chronic HCV infection, using preference-based (utilities) and non-preference-based methods of evaluating QOL.

METHODS

In a tertiary care setting, 271 patients completed a self-administered time trade-off utility instrument, the Health Utility Index Mark 2 and Mark 3, and the Hepatitis Quality of Life Questionnaire Version 2. Mean QOL scores were compared across HCV disease stages and sociodemographical categories. We examined the association between QOL and disease stage using linear regression adjusting for age, education, marital status, log income and Charlson comorbidity scores. Mean utility scores were compared across disease stages using a propensity score method.

RESULTS

Mean utilities were lower than general population norms (0.81-0.92) and ranged from 0.62 to 0.82 in non-cirrhotic patients (n=197), 0.56-0.84 in compensated cirrhotic patients (n=17) and 0.55-0.76 for decompensated cirrhotic patients (n=57). No significant association found was between disease stage and utility for current health status. Higher income, fewer comorbidities and living in a married or common-law relationship were significantly associated with higher utilities and better QOL. No significant difference in utilities was found between disease stages using propensity score matching.

CONCLUSIONS

Our study confirms that changes in HCV disease stage explain only small changes in QOL and suggests that factors such as underlying comorbidities, income and marital status have a greater effect on QOL than disease stage.

Addition of adult-to-adult living donation to liver transplant programs improves survival but at an increased cost

Using outcomes data from the Adult-to-Adult Living Donor Liver Transplantation Cohort Study, we performed a cost-effectiveness analysis exploring the costs and benefits of living donor liver transplantation (LDLT). A multistage Markov decision analysis model was developed with treatment, including medical management only (strategy 1), waiting list with possible deceased donor liver transplantation (DDLT; strategy 2), and waiting list with possible LDLT or DDLT (strategy 3) over 10 years. Decompensated cirrhosis with medical management offered survival of 2.0 quality-adjusted life years (QALYs) while costing an average of $65,068, waiting list with possible DDLT offered 4.4-QALY survival and a mean cost of $151,613, and waiting list with possible DDLT or LDLT offered 4.9-QALY survival and a mean cost of $208,149. Strategy 2 had an incremental cost-effectiveness ratio (ICER) of $35,976 over strategy 1, whereas strategy 3 produced an ICER of $106,788 over strategy 2. On average, strategy 3 cost $47,693 more per QALY than strategy 1. Both DDLT and LDLT were cost-effective compared to medical management of cirrhosis over our 10-year study period. The addition of LDLT to a standard waiting list DDLT program is effective at improving recipient survival and preventing waiting list deaths but at a greater cost.

Beyond utilitarianism: a method for analyzing competing ethical principles in a decision analysis of liver transplantation

BACKGROUND

The utilitarian foundation of decision analysis limits its usefulness for many social policy decisions. In this study, the authors examine a method to incorporate competing ethical principles in a decision analysis of liver transplantation for a patient with acute liver failure (ALF).

METHODS

A Markov model was constructed to compare the benefit of transplantation for a patient with ALF versus the harm caused to other patients on the waiting list and to determine the lowest acceptable 5-y posttransplant survival for the ALF patient. The weighting of the ALF patient and other patients was then adjusted using a multiattribute variable incorporating utilitarianism, urgency, and other principles such as fair chances.

RESULTS

In the base-case analysis, the strategy of transplanting the ALF patient resulted in a 0.8% increase in the risk of death and a utility loss of 7.8 quality-adjusted days of life for each of the other patients on the waiting list. These harms cumulatively outweighed the benefit of transplantation for an ALF patient having a posttransplant survival of less than 48% at 5 y. However, the threshold for an acceptable posttransplant survival for the ALF patient ranged from 25% to 56% at 5 y, depending on the ethical principles involved.

DISCUSSION

The results of the decision analysis vary depending on the ethical perspective. This study demonstrates how competing ethical principles can be numerically incorporated in a decision analysis.

Health-state utilities in liver disease: a systematic review

OBJECTIVES

Health-state utilities are essential for cost-utility analysis. Few estimates exist for liver disease in the literature. The authors' aim was to conduct a systematic review of health-state utilities in liver disease, to look at the variation of study designs used, and to pool utilities for some liver disease states.

METHODS

A search of MED-LINE, EMBASE, and CINAHL from 1966 to September 2006 was conducted including key words related to liver disease and utility measuring tools. Articles were included if health-state utility tools or expert opinion were used. Variance-weighted mean utility estimates were pooled using metaregression adjusting for disease state and utility assessment method.

RESULTS

Thirty studies measured utilities of liver diseases/disease states. Half of these estimated utilities for hepatitis viruses: hepatitis A (n = 1), hepatitis B (n = 4), and hepatitis C (n = 10). Others included liver transplant (n= 6) and chronic liver disease (n= 5) populations. Twelve utility methods were used throughout. The EQ-5D (n = 10) was most popular method, followed by visual analogue scale (n = 9), time tradeoff (n = 6), and standard gamble (n = 4). Respondents were patients (n= 16), an expert panel (n = 10), non-liver diseases adults ( n=2), patient and expert (n = 1), and patient and healthy adult (n = 1). Type of perspective included community (n=21), patient (n=4), and both (n = 5). The pooled mean estimates in hepatitis C with moderate disease, compensated cirrhosis, decompensated cirrhosis, and post-liver transplant using the EQ-5D were 0.75, 0.75, 0.67, and 0.71, respectively. The change in these utilities using different methods were -0.07 (visual analogue scale), -0.01 (health utilities index version 3), +0.04 (standard gamble), + 0.08 (health utilities index version 2), + 0.12 (time tradeoff), and + 0.15 (standard gamble-transformed visual analogue scale).

CONCLUSIONS

The authors have created a valuable liver disease- based utility resource from which researchers and policy makers can easily view all available utility estimates from the literature. They have also estimated health-state utilities for major states of hepatitis C.

A novel model measuring the harm of transplanting hepatocellular carcinoma exceeding Milan criteria

No empirical studies have defined the posttransplant survival that would justify expansion of the Milan criteria for liver transplantation of hepatocellular carcinoma. We created a Markov model comparing the survival benefit of transplantation for a patient with >Milan HCC, versus the harm caused to other patients on the waiting list. In the base-case analysis, the strategy of transplanting the patient with >Milan HCC resulted in a 44% increased risk of death and a utility loss of 3 quality-adjusted years of life across the pre- and posttransplant periods for a nationally representative cohort of patients on the waiting list. This harm outweighed the benefit of transplantation for a patient with >Milan HCC having a 5-year posttransplant survival of less than 61%. This survival threshold was most sensitive to geographic variations in organ shortage, with the threshold varying from 25% (Region 3) to >72% (Regions 1, 5, 7 and 9). In conclusion, expansion of the Milan criteria will require demonstrating high survival rates for the newly eligible patients-approximately 61% at 5 years after transplantation. In regions with less severe organ shortage, a more aggressive approach to transplanting these patients may be justified.

Preliminary testing of a just-in-time, user-defined values clarification exercise to aid lower literate women in making informed breast cancer treatment decisions

OBJECTIVE

To report on the initial testing of a values clarification exercise utilizing a jewellery box within a computerized patient decision aid (CPtDA) designed to assist women in making a surgical breast cancer treatment decision.

DESIGN

Pre-post design, with patients interviewed after diagnosis, and then after completing the CPtDA sometime later at their preoperative visit.

SAMPLE

Fifty-one female patients, who are low literate and naïve computer users, newly diagnosed with early stage breast cancer from two urban public hospitals.

INTERVENTION

A computerized decision aid that combines entertainment-education (edutainment) with enhanced (factual) content. An interactive jewellery box is featured to assist women in: (1) recording and reflecting over issues of concern with possible treatments, (2) deliberating over surgery decision, and (3) communicating with physician and significant others.

OUTCOMES

Patients' use of the jewellery box to store issues during completion of the CPtDA, and perceived clarity of values in making a treatment decision, as measured by a low literacy version of the Decisional Conflict Scale (DCS).

RESULTS

Over half of the participants utilized the jewellery box to store issues they found concerning about the treatments. On average, users flagged over 13 issues of concern with the treatments. Scores on the DCS Uncertainty and Feeling Unclear about Values subscales were lower after the intervention compared to before the decision was made.

CONCLUSIONS

A values clarification exercise using an interactive jewellery box may be a promising method for promoting informed treatment decision making by low literacy breast cancer patients.

A clinically based discrete-event simulation of end-stage liver disease and the organ allocation process

BACKGROUND

The optimal allocation of scarce donor livers is a contentious health care issue requiring careful analysis. The objective of this article was to design a biologically based discrete-event simulation to test proposed changes in allocation policies.

METHODS

The authors used data from multiple sources to simulate end-stage liver disease and the complex allocation system. To validate the model, they compared simulation output with historical data.

RESULTS

Simulation outcomes were within 1% to 2% of actual results for measures such as new candidates, donated livers, and transplants by year. The model overestimated the yearly size of the waiting list by 5% in the last year of the simulation and the total number of pretransplant deaths by 10%.

CONCLUSION

The authors created a discrete-event simulation model that represents the biology of end-stage liver disease and the health care organization of transplantation in the United States.

Measuring utilities by the time trade-off method in Tunisian rheumatoid arthritis patients

The objective of this study was to determine the feasibility, reliability and validity of the time trade-off (TTO) in Tunisian rheumatoid arthritis (RA) patients. The TTO was used to measure the utility in 122 RA patients with increasing difficulty in performing activities of daily living. The 1-week test-retest reproducibility was studied in 57 patients using the intraclass correlation coefficient (ICC). Validity was evaluated by comparison with other outcome measures: utility rating scale (RS), quality of life (QOL) [arthritis impact measurement scale 2 (AIMS2), rheumatoid arthritis quality of life (RAQOL)], functional status [health assessment questionnaire (HAQ), Lee index] and disease activity score (DAS). Eight patients (6.6%) did not complete the TTO. The median value of the TTO score was 0.655 (0.019-1.000). The ICC for reliability of the TTO was 0.89 (p<0.001). The TTO showed poor to moderate correlation (Spearman's correlation coefficients between 0.2 and 0.409, p<0.01) with AIMS2, RAQOL, HAQ and Lee index. We did not find any correlation between TTO and DAS. Multiple regression analysis showed that only 32% of TTO scores could be explained. The TTO method appeared to be reliable in a group of Tunisian RA patients, but TTO values were poorly to moderately related to measures of QOL, functional ability, and disease activity. We think that TTO and RS are not feasible for use in RA patients.