Calculation Of Quality-adjusted Life-years Research Articles

Using the health assessment questionnaire to estimate preference‐based single indices in patients with rheumatoid arthritis

To estimate the relationship between preference-based measures, EuroQol (EQ-5D) and SF-6D, and the Health Assessment Questionnaire (HAQ) disability index (DI) in patients with rheumatoid arthritis (RA), and to characterize components that are predictors of health utility. Patients with RA participating in 2 studies in the UK (n = 151) and Canada (n = 319) completed the HAQ, EQ-5D, and Short Form 36 (SF-36). The SF-36, a generic measure of quality of life, was converted into the preference-based SF-6D. From these results we developed models of the relationship between the HAQ and SF-6D and EQ-5D using various regression analyses. The optimal model developed for the EQ-5D entered levels for each item as independent variables (model 5). A root mean square error (RMSE) of 0.18 suggested relatively good predictive ability. For the SF-6D, RMSEs were lower (0.09), suggesting better predictions than for the EQ-5D, but models with more explanatory variables did not improve results (model 2 or 4 optimal). The models were able to predict actual SF-6D and EQ-5D across the range of the HAQ DI. Our approach enabled calculations of quality-adjusted life years from existing trials where only the HAQ was measured. All aspects of the HAQ may not be reflected in the preference-based measures, and this method is suboptimal to direct measurement of health state utility in clinical trials. Given this limitation, our approach provides an alternative for researchers who need health-state utility values, but had not included a preference-based measure in their clinical study because of resource constraints or a desire to limit patient burden.

Cost-effectiveness analysis of the EORTC 24971 (TAX 323) trial comparing docetaxel plus cisplatin and 5-fluorouracil versus standard treatment (cisplatin and 5-fluorouracil) as induction chemotherapy followed by radiation therapy in locally advanced unresectable squamous cell carcinoma of the head and neck (SCCHN)

6090 Background: The phase III EORTC 24971 clinical trial (TAX 323) showed that induction chemotherapy followed by radiation therapy increases time to progression and improves outcomes in unresectable SCCHN patients. [Remenar et al. ASCO 2006; Abs 5516] Induction chemotherapy with cisplatin/5-FU (PF) is a standard regimen for patients with locally advanced SCCHN. The economic impact of adding docetaxel to cisplatin/5-FU (TPF) in this setting was assessed using a Markov state-transition model. Methods: The Markov model includes four health states (based on WHO criteria for measuring objective response): stable, response, progression, and death. Efficacy data from the TAX 323 clinical trial were used to derive transition probabilities between the health states. Adverse event rates were also derived from TAX 323. Data for resource utilization and costs for the UK were derived from the literature and from an advisory board of clinicians. In order to calculate quality adjusted life years (QALYs), utilities were derived by mapping the global score on the Health Related Quality of Life Questionnaire Core-30 (QLQ-C30) to the EQ-5D. Results: Patients survived longer in the TPF arm versus PF (2.5 vs. 2.0 years). Total costs for TPF and PF were £31,203 and £26,944, respectively. The incremental discounted cost per QALY gained for TPF versus PF was £9,859/QALY, which is below the £20,000 cost-effectiveness threshold suggested by NICE as a guide to the acceptability of a technology. Conclusion: Docetaxel, when given as induction chemotherapy in combination with cisplatin/5-FU, is cost-effective compared with PF in locally advanced unresectable SCCHN patients. Treating SCCHN patients with TPF followed by radiation represents good value for money based on the results of the analysis. No significant financial relationships to disclose.

What difference does it make? The calculation of QALY gains from health profiles using patient and general population values

Objectives To compare the Quality-Adjusted Life Year (QALY) values produced from a direct health profile QALY calculation method, using patient values, with those derived from a conventional QALY calculation method, using general population values. Methods Comparison of QALY values generated from patient valuations of health profiles, using a chained version of the Time Trade-Off method, with QALY values derived from a conventional QALY calculation method, using general population values of EQ-5D states, an observational survey of MS patients, and a randomized controlled trial. Results Using patient valuations of health profiles, QALY values of treatment and placebo were 2.610 and 2.568, respectively, generating a gain of 0.042. The conventional QALY method gave values of 2.042 versus 1.998, producing a gain of 0.044. These findings were generally robust under sensitivity analyses. Conclusions QALY values were dependent on the calculation method used, but QALY gains were similar between methods. QALY values from the conventional QALY calculation method appeared robust to most changes in the assumptions used to derive values. The direct health profile QALY method was however more able to account for heterogeneity in preferences.

Cost-effectiveness and cost-utility of insulin glargine compared with NPH insulin based on a 10-year simulation of long-term complications with the Diabetes Mellitus Model in patients with type 2 diabetes in Switzerland

The objective of this study was to evaluate the cost-effectiveness of insulin glargine compared with NPH insulin in patients with type 2 diabetes and in whom OAD (oral anti-diabetics) had failed in Switzerland. Long-term diabetes outcomes were simulated with the Diabetes Mellitus Model (DMM) over a period of 10 years. The incidences of long-term complications (micro- and macrovascular events) were simulated for 10,000 patients over 10 years for six different scenarios. The scenarios were based on HbA1c reductions observed in clinical trials. For insulin glargine, HbA1c reductions of 0.96% (pessimistic case) and 1.24% (optimistic case) were simulated for three different HbA1c baseline values (10, 9 and 8%). For NPH insulin the HbA1c reduction was assumed to be 0.84%. A cost model and a utility model were developed in order to use the cumulated incidences of the simulations for the calculation of cost and QALYs (quality-adjusted life years). The unit costs of micro- and macrovascular events were assessed on the basis of published literature and guideline-projected resource-use estimations for Switzerland. Disutility values of diabetes-related long-term complications were derived from the literature. Total direct medical costs or QALYs were assessed by a combination of cumulated incidences of each event up to 10 years with the corresponding unit cost per event (in addition to the acquisition cost) or with disutility values per event, respectively. Events, total cost, and QALYs were discounted at 3%. In scenarios where no savings could be shown for insulin glargine, incremental cost-effectiveness ratios were calculated as the incremental cost per event prevented and the cost per QALY gained. Cost comparison demonstrated that insulin glargine is the dominant strategy for the optimistic case scenario starting at a baseline HbA1c value of 10% as savings in the management of complications exceeded the difference in acquisition costs after 8 years of treatment. Optimistic case scenarios for baseline HbA1c values of 9 and 8% achieved costs per QALY gained amounting to CHF 2,853 and CHF 5,711 and costs per event prevented amounting to CHF 2,054 and CHF 4,899, respectively. Pessimistic case scenarios for baseline HbA1c values of 10, 9 and 8% resulted in costs per QALY gained amounting to CHF 40,441, CHF 45,701 and CHF 49,468 and costs per event prevented amounting to CHF 27,742, CHF 32,451 and CHF 41,620, respectively. This study investigated the long-term health-economic implications of treating type 2 diabetes patients, in whom OAD had failed, with insulin glargine versus NPH insulin in Switzerland. The 10-year simulations demonstrated that the deltaHbA1c reductions of 0.4 and 0.12% achieved with insulin glargine led to a reduction of long-term complications, mortality and associated costs as well as to an improved quality of life. Insulin glargine proved to be cost-effective and represents good to excellent value for money compared to NPH insulin.

Not all “quality-adjusted life years” are equal

Background There is evidence that utility elicitation methods used in the calculation of quality-adjusted life years (QALYs) yield different results. It is not clear how these differences impact economic evaluations. Methods Using a mathematical model incorporating data on efficacy, costs, and utility values, we simulated the experiences of 100,000 hypothetical rheumatoid arthritis patients over 10 years (50,000 exposed to infliximab plus methotrexate [MTX] and 50,000 exposed to MTX alone). QALYs, were derived from the Health Utilities Index 2 and 3 (HUI2 and HUI3), the Short Form 6-D (SF-6D), and the Euroqol 5-D (EQ-5D). Incremental cost-utility ratios were determined using each instrument to calculate QALYs and the results were compared using cost-effectiveness acceptability curves. Results Using the different utility measurement methods, the mean difference in QALYs between the infliximab plus MTX and MTX groups ranged from a high of 1.95 QALYs (95% CI = 1.93–1.97) using the HUI3 to 0.89 QALYs (95% CI = 0.88–0.91) using the SF-6D. Adopting the commonly cited value of society's willingness to pay for a QALY of $50,000, 91% of the simulations favored the cost utility of infliximab plus MTX when using the HUI3 to calculate QALYs. However, when using the EQ-5D, HUI2, or the SF-6D utility values to calculate QALYS, the proportion of simulations that favored the cost utility of infliximab were 63%, 45%, and 12%, respectively. Conclusion Depending on the method for determining utility values used in the calculation of QALYs, very different incremental cost-utility ratios are generated.

Wie werden in deutschen Studien qualitätsadjustierte Lebensjahre definiert?

Cost-utility analysis, a way of evaluating health-economic data, is of increasing importance in Germany. It was the aim of this study to provide a systematic survey of all published cost-utility studies on the German health system. In addition to collecting general study characteristics, particular attention was paid to three questions: (1) On what populations are the utility values based that are necessary for calculating quality-adjusted life years (QALYs); (2) by what method were the data generated; and (3) how was the construction of the health-related results documented? In the course of systematically reviewing all German health-economic evaluations, cost-utility studies published between 1990 and 2004 were identified. For this purpose both generic and specific health-economic databanks were searched using clearly defined criteria. The fulfillment of explicit criteria for inclusion and exclusion were tested and relevant items of information extracted from the full text. Among 730 studies for which the full text was analysed 18 cost-utility studies were identified. Most of them were in medical journals in English and their objective was to evaluate curative medical interventions. The methods used for generating utility values differed greatly between them and in general were inadequately documented. Most cost-utility studies combine utility values that were generated from different perspectives and countries of origin. In addition they used different methods of assessment. As a rule the methods for determining utility values were not transparent and inadequately documented. The calculations of QALYs based on these studies are not comparable. Most of the studies cannot be assumed to reflect the utility of medical care in respect to German patients or the German population.

Calculating QALYs, comparing QALY and DALY calculations

Quality-adjusted life years (QALYs) have been used in the assessment of health interventions for three decades. The popularity of the QALY approach has been constantly increasing, although the debate on its theoretical underpinnings and practical implications is still ongoing. Disability-adjusted life years (DALYs), also widely debated, were shaped some 20 years later, broadly within the same conceptual framework but with a number of important differences. This paper provides a comprehensive formulation of QALY calculation methods, offering practical instruments for assessing the impact of health interventions, similar to those made available elsewhere for calculating DALYs. Systematic differences between QALYs and DALYs are explained by reference to two examples: the prevention of tuberculosis and the treatment of bipolar depression. When a health intervention is aimed at preventing or treating a non-fatal disease, the relationship between QALYs gained and DALYs saved depends on age of onset and duration of the disease, as well as the quality of life and disability weights. In the case of a potentially fatal disease, a larger number of factors may determine differences between outcomes assessed with the two metrics. The relative importance of some of these factors is discussed and illustrated graphically in the paper. Understanding similarities and differences between QALYs and DALYs is important to researchers and policy makers, for a sound interpretation of the evidence on the outcomes of health interventions.

Cost-Utility Analysis of Physiotherapy Treatment Compared With Physiotherapy Advice in Low Back Pain

Economic evaluation alongside a pragmatic multicenter randomized controlled trial from the National Health Service (NHS) and societal perspective. To perform a cost-utility analysis of routine physiotherapy treatment compared with an assessment session and advice from a physiotherapist for patients with subacute and chronic low back pain. Lack of evidence for some types of physiotherapy intervention and a paucity of cost-effectiveness data for treatment of low back pain has led to controversy and uncertainty within the medical and allied professions. A total of 286 patients with low back pain of more than a 6-week duration were randomized to physiotherapy treatment or advice on remaining active from a physiotherapist. Data were collected on back pain-related NHS and patients' costs over a 12-month post randomization period. The primary outcome measure was the Oswestry Disability Index at 12 months, with additional Oswestry Disability Index measures at 2 and 6 months. The EuroQol EQ-5D was used to calculate quality adjusted life years. Cost-effectiveness was expressed as the incremental cost per quality adjusted life year gained. Uncertainty was handled using confidence ellipses for the ratio and cost-effectiveness acceptability curves. The total NHS costs were not significantly different at 179 pounds sterling (221 pounds sterling) for physiotherapy and 159 pounds sterling (260 pounds sterling) for the advice group. However, patients in the physiotherapy group had significantly higher out-of-pocket health care expenditure (40 pounds sterling, 95% confidence interval 9 pounds sterling to 71 pounds sterling). Utility levels improved in both groups from baseline to 12 months, with no significant differences between groups. The results indicate no significant differences in either NHS costs or effects. However, the significantly higher out-of-pocket expenses incurred by patients receiving routine physiotherapy suggests that advice given by a physiotherapist should be considered as the first-line treatment for patients with this level of back pain disability.

A Cost/Utility Analysis of Open Reduction and Internal Fixation versus Cast Immobilization for Acute Nondisplaced Mid-Waist Scaphoid Fractures

Open reduction and internal fixation and cast immobilization are both acceptable treatment options for nondisplaced waist fractures of the scaphoid. The authors conducted a cost/utility analysis to weigh open reduction and internal fixation against cast immobilization in the treatment of acute nondisplaced mid-waist scaphoid fractures. The authors used a decision-analytic model to calculate the outcomes and costs of open reduction and internal fixation and cast immobilization, assuming the societal perspective. Utilities were assessed from 50 randomly selected medical students using the time trade-off method. Outcome probabilities taken from the literature were factored into the calculation of quality-adjusted life-years associated with each treatment. The authors estimated medical costs using Medicare reimbursement rates, and costs of lost productivity were estimated by average wages obtained from the U.S. Bureau of Labor Statistics. Open reduction and internal fixation offers greater quality-adjusted life-years compared with casting, with an increase ranging from 0.21 quality-adjusted life-years for the 25- to 34-year age group to 0.04 quality-adjusted life-years for the > or =65-year age group. Open reduction and internal fixation is less costly than casting ($7940 versus $13,851 per patient) because of a longer period of lost productivity with casting. Open reduction and internal fixation is therefore the dominant strategy. When considering only direct costs, the incremental cost/utility ratio for open reduction and internal fixation ranges from $5438 per quality-adjusted life-year for the 25- to 34-year age group to $11,420 for the 55- to 64-year age group, and $29,850 for the > or =65-year age group. Compared with casting, open reduction and internal fixation is cost saving from the societal perspective ($5911 less per patient). When considering only direct costs, open reduction and internal fixation is cost-effective relative to other widely accepted interventions.

Rapid Benefit‐Risk Assessments: No Escape from Expert Judgments in Risk Management

The "human health impacts assessment" described by Cox and Popken (this issue) is intended to be a benefit-risk tool that avoids pitfalls of using expert judgments for policy analysis or during strict application of the precautionary principle in risk management. The proposed benefit-risk calculation uses numerous assumptions and suppositions to calculate a ratio of quality-adjusted life years (QALYs) lost for the number of human illness days prevented by the use of a food-animal antimicrobial drug, to the number of human illness days caused by the use of the antimicrobial drug. Assumptions about data--e.g., expert judgments on the representativeness of parameter estimates--are commonly used in risk assessment and risk management, including Cox and Popken's method. Cox and Popken apply the technique to specific examples of enrofloxacin and macrolides antimicrobial drugs, sometimes used in broiler chickens for human food. Although enthusiastically portrayed as a straightforward calculation of QALYs lost for two decision alternatives, Cox and Popken were silent on the pivotal expert judgment subsumed in their method: quality weights for illnesses caused by antimicrobial-resistant and antimicrobial-sensitive microbes are tacitly assumed to be equal. Yet, the costs in terms of prolonged illness, additional medications, repeat medical visits, and dread of more serious sequelae are expected to differ substantially for antimicrobial-resistant versus antimicrobial-sensitive illnesses. Despite their enthusiasm to the contrary, the "human health impacts assessment" by Cox and Popken is not immune from expert judgments in risk management.

Surgical stabilisation of the spine compared with a programme of intensive rehabilitation for the management of patients with chronic low back pain: cost utility analysis based on a randomised controlled trial

Objective To determine whether, from a health provider and patient perspective, surgical stabilisation of the spine is cost effective when compared with an intensive programme of rehabilitation in patients with...

Development of the multi-attribute Pediatric Asthma Health Outcome Measure (PAHOM)

To develop a multi-attribute outcome measure for children with asthma that allows for the calculation of quality-adjusted life years in cost-effectiveness studies and can also be used to assign preference weights to asthma-symptom-free days. A literature review and two interviewer-administered surveys. Homes or community centers of participants in Seattle, United States. Visual analog scale (VAS), standard gamble (SG), and relative risk attitude equation techniques were used to estimate two sets of preference weights for 10 health states. The PAHOM was used to record health states of pediatric asthma patients. A total of 94 subjects provided complete responses without any illogical ratings to VAS questions and 101 provided the same to SG questions. The VAS preference weights of the health states range from a maximum of 1 for perfect health to a minimum of 0.03 for severe asthma symptoms, emotional problems, and activity limitations. Those based on the relative risk attitude equation constructed with both VAS and SG preference weights range from 1 to 0.06. The mean PAHOM scores of pediatric asthma patients based on VAS and converted SG preference weights were 0.70 and 0.83, respectively. The PAHOM calendar can be used to identify asthma patients' health outcomes, to calculate the preference weights of asthma patients' health states, and to estimate the number of symptom-free days. These factors make the PAHOM a promising instrument for use in effectiveness and cost-effectiveness studies in children with asthma.

Cost-effectiveness analysis of telemedicine to evaluate diabetic retinopathy in a prison population

A Cost-effectiveness analysis was conducted to investigate the clinical and economic impact of teleophthalmology in evaluating diabetic retinopathy in prison inmates with type 2 diabetes. Based on a hypothetical teleophthalmology system to evaluate diabetic retinopathy patients with type 2 diabetes in a prison care setting, a Markov decision model was developed with probability and cost data derived primarily from published epidemiological and outcome studies. A 40-year-old African-American man with type 2 diabetes was used as a reference case subject. The number of quality-adjusted life-years (QALYs) gained was used as the clinical outcome, and the cost in U.S. dollars from the year 2003 was used as the economic outcome. Teleophthalmology and nonteleophthalmology strategies were compared using an expected QALYs calculation and two types of sensitivity analyses: probabilistic and traditional n-way sensitivity analyses. The teleophthalmology strategy dominates in the cost-effectiveness analysis for the reference case subject: 16,514/18.73 dollars QALYs for teleophthalmology and 17,590/18.58 dollars QALYs for nonteleophthalmology. Ninety percent of the Monte Carlo simulations showed cost effectiveness (annual cost/QALYs ≤ 50,000 dollars) in the teleophthalmology strategy based on an assumed inmate population. Teleophthalmology is the better strategy if the number of diabetic inmates in the prison community is >500. This cost-effectiveness analysis demonstrates that teleophthalmology holds great promise to reduce the cost of inmate care and reduce blindness caused by diabetic retinopathy in type 2 diabetic patients.—Hans E. Grossniklaus

Intensive rehabilitation may be more cost effective than surgical stabilisation for chronic low back pain

From the perspectives of health providers and chronic low back pain patients, is surgical stabilisation (spinal fusion) cost effective when compared with intensive rehabilitation? Economic evaluation alongside a pragmatic randomised controlled trial. 15 UK orthopaedic and rehabilitation centres. 349 participants aged 18–55 years, with chronic low back pain lasting at least one year, who were considered candidates for spinal fusion, were randomly assigned to either lumbar spine fusion (176 participants of whom 139 received it) or an intensive rehabilitation program based on cognitive behavioural therapy principles (173 participants of whom 151 received it). The difference reflects 38 patients allocated to rehabilitation who chose surgery, and seven surgery patients who chose rehabilitation then surgery. Costs related to back pain, incurred by patients and National Health Service over the 24 months of the study, return to paid employment, total hours worked, and EuroQol EQ-5D to calculate quality adjusted life years (QALYs). Mean total cost per patient was £7830 (SD £5202) in the surgery group, compared with £4526 (SD £4155) for the rehabilitation group (significant difference in favour of rehabilitation £3304 (95% CI £2317–£4291). There was no significant difference between groups in QALYs 0.07 (–0.02 to 0.16). Incremental cost effectiveness ratio was £48,588 per QALY gained (–£279,883 to £372,406). Spinal stabilisation surgery appears to be less cost effective than rehabilitation programs based on cognitive behavioural therapy over a two year follow-up period. Further follow-up is required to track the number of rehabilitation patients who require surgery.

Estimating mean QALYs in trial‐based cost‐effectiveness analysis: the importance of controlling for baseline utility

In trial-based cost-effectiveness analysis baseline mean utility values are invariably imbalanced between treatment arms. A patient's baseline utility is likely to be highly correlated with their quality-adjusted life-years (QALYs) over the follow-up period, not least because it typically contributes to the QALY calculation. Therefore, imbalance in baseline utility needs to be accounted for in the estimation of mean differential QALYs, and failure to control for this imbalance can result in a misleading incremental cost-effectiveness ratio. This paper discusses the approaches that have been used in the cost-effectiveness literature to estimate absolute and differential mean QALYs alongside randomised trials, and illustrates the implications of baseline mean utility imbalance for QALY calculation. Using data from a recently conducted trial-based cost-effectiveness study and a micro-simulation exercise, the relative performance of alternative estimators is compared, showing that widely used methods to calculate differential QALYs provide incorrect results in the presence of baseline mean utility imbalance regardless of whether these differences are formally statistically significant. It is demonstrated that multiple regression methods can be usefully applied to generate appropriate estimates of differential mean QALYs and an associated measure of sampling variability, while controlling for differences in baseline mean utility between treatment arms in the trial.

Quality-adjusted survival: a rigorous assessment of cure after cancer during childhood and adolescence.

Survivors of cancer in childhood and adolescence, while increasing gratifyingly in number with ever more effective therapy, have a life expectancy that is compromised all-too-often in both duration and value as a result of adverse treatment-related sequelae. Accounting for this burden of morbidity and mortality is essential for a proper appreciation of cure. Adjusting estimates of survival by measures of its quality affords a means of accomodating this requirement. It can be accomplished by "weighting" the length of survival according to preference-based assessments of health-related quality of life (HRQL), which allow the calculation of quality-adjusted life years. Inclusion of measures of HRQL in clinical trials is imperative as we reach to the ultimate objective; the truly cured child restored to normal health.

Cost-effectiveness analysis of telemedicine to evaluate diabetic retinopathy in a prison population.

A cost-effectiveness analysis was conducted to investigate the clinical and economic impact of teleophthalmology in evaluating diabetic retinopathy in prison inmates with type 2 diabetes. Based on a hypothetical teleophthalmology system to evaluate diabetic retinopathy patients with type 2 diabetes in a prison care setting, a Markov decision model was developed with probability and cost data derived primarily from published epidemiological and outcome studies. A 40-year-old African-American man with type 2 diabetes was used as a reference case subject. The number of quality-adjusted life-years (QALYs) gained was used as the clinical outcome, and the cost in U.S. dollars from the year 2003 was used as the economic outcome. Teleophthalmology and nonteleophthalmology strategies were compared using an expected QALYs calculation and two types of sensitivity analyses: probabilistic and traditional n-way sensitivity analyses. The teleophthalmology strategy dominates in the cost-effectiveness analysis for the reference case subject: 16,514/18.73 dollars QALYs for teleophthalmology and 17,590/18.58 dollars QALYs for nonteleophthalmology. Ninety percent of the Monte Carlo simulations showed cost effectiveness (annual cost/QALYs < or = 50,000 dollars) in the teleophthalmology strategy based on an assumed inmate population. Teleophthalmology is the better strategy if the number of diabetic inmates in the prison community is >500. Our cost-effectiveness analysis demonstrates that teleophthalmology holds great promise to reduce the cost of inmate care and reduce blindness caused by diabetic retinopathy in type 2 diabetic patients.

Calculation of quality adjusted life years in the published literature: a review of methodology and transparency.

Economic evaluations alongside randomised controlled trials (RCTs) are increasingly being designed to prospectively collect patient-specific resource use and preference-based health status (utility) data. This paper examines the ways in which preference-based health status (utility) data are used to generate quality adjusted life years (QALYs). A literature review was carried out which identified 23 published cost utility analyses suitable for inclusion. The methodology employed to calculate QALYs was not always consistent, as well as being poorly reported. The use of different methodologies in the calculation of QALYs may influence the magnitude and direction of results of evaluations. Analysts need to be consistent and fully transparent in the methodology chosen to calculate QALYs.

Variation in the estimation of quality-adjusted life-years by different preference-based instruments.

To assess the interchangeability of preference-based health-related quality of life tools and compare the potential gains in quality-adjusted life years (QALYs) in patients with musculoskeletal disease. Consecutive patients visiting a rheumatology clinic completed health-related quality of life assessments at baseline and 3, 6, and 12 months with the EuroQol (EQ-5D), Health Utilities Index (HUI3), and Short-Form 6D (SF-6D). Patients rated their health changes retrospectively and responses were categorized into three groups: better, same, and worse. Correlations and repeated measures analysis of variance with post hoc contrasts and a Bonferroni correction were used to assess interchangeability of tools. Results were based on 161 cases with complete baseline data and 98 cases with data at baseline and 12 months. Correlations ranged from 0.66 to 0.79. An interaction effect showed that for the better group, the EQ-5D showed a significantly greater mean improvement (0.15) than the HUI3 (0.07) or the SF-6D (0.05). For the worse group, the EQ-5D showed a significantly greater mean decrease (0.19) than either the HUI3 (0.05) or the SF-6D (0.03). QALYs differences between the better and worse groups were significantly greater (0.23) with the EQ-5D than with the HUI3 (0.11) or the SF-6D (0.09). Although results moderately support the idea that the three tools are measuring a similar underlying construct, the tools are not interchangeable because they are scaled differently and produce varying results. These findings have potential implications for the interpretation and comparability of health outcome studies and economic analyses. Possible approaches are sensitivity analysis or standardization of scores before calculation of QALYs.

Testing assumptions of quality-adjusted life-year calculations

Testing assumptions of quality-adjusted life-year calculations