Continuous-risk utility assessment in medical decision making

Methods for Performing Survival Curve Quality-of-Life Assessments

BACKGROUND

Many medical decisions involve an implied choice between alternative survival curves, typically with differing quality of life. Common preference assessment methods neglect this structure, creating some risk of distortions.

METHODS

Survival curve quality-of-life assessments (SQLA) were developed from Gompertz survival curves fitting the general population's survival. An algorithm was developed to generate relative discount rate-utility (DRU) functions from a standard survival curve and health state and an equally attractive alternative curve and state. A least means squared distance algorithm was developed to describe how nearly 3 or more DRU functions intersect. These techniques were implemented in a program called X-Trade and tested.

RESULTS

SQLA scenarios can portray realistic treatment choices. A side effect scenario portrays one prototypical choice, to extend life while experiencing some loss, such as an amputation. A risky treatment scenario portrays procedures with an initial mortality risk. A time trade scenario mimics conventional time tradeoffs. Each SQLA scenario yields DRU functions with distinctive shapes, such as sigmoid curves or vertical lines. One SQLA can imply a discount rate or utility if the other value is known and both values are temporally stable. Two SQLA exercises imply a unique discount rate and utility if the inferred DRU functions intersect. Three or more SQLA results can quantify uncertainty or inconsistency in discount rate and utility estimates. Pilot studies suggested that many subjects could learn to interpret survival curves and do SQLA.

LIMITATIONS

SQLA confuse some people. Compared with SQLA, standard gambles quantify very low utilities more easily, and time tradeoffs are simpler for high utilities. When discount rates approach zero, time tradeoffs are as informative and easier to do than SQLA.

CONCLUSIONS

SQLA may complement conventional utility assessment methods.

Cost-effectiveness analysis of periacetabular osteotomy

BACKGROUND

A lack of long-term outcomes data following periacetabular osteotomy makes it difficult for surgeons to recommend the most appropriate procedure to young patients who might be candidates for a joint-preserving procedure. In this study, we compared the cost-effectiveness of periacetabular osteotomy with total hip arthroplasty in terms of cost per quality-adjusted life year for the young adult.

METHODS

A decision model was constructed for a cost-utility analysis of periacetabular osteotomy compared with total hip arthroplasty. Outcome probabilities and effectiveness were derived from the literature. Effectiveness was expressed in quality-adjusted life years gained. Cost data were compiled and verified from our institution. Costs and utilities were discounted in accord with the United States Panel on Cost-Effectiveness in Health and Medicine. Principal outcome measures were average incremental costs, incremental effectiveness, incremental quality-adjusted life years, and net health benefits. Multivariate sensitivity analysis was used to assess the contribution of included variables in the model's outcomes.

RESULTS

For Tönnis grade-1 coxarthrosis, periacetabular osteotomy dominates with an average incremental cost-effectiveness of $7856 per quality-adjusted life year and an average incremental effectiveness of 0.15. For Tönnis grade-2 coxarthrosis, periacetabular osteotomy is, on the average, more cost-effective than total hip arthroplasty with an incremental cost-effectiveness of $824 per quality-adjusted life year, but it is less effective than total hip arthroplasty, on the average, with an incremental effectiveness of -1.4 quality-adjusted life years. Periacetabular osteotomy becomes more cost-effective at a longevity of 5.5 years for Tönnis grade-1 coxarthrosis and 18.25 years for Tönnis grade-2 coxarthrosis. In Tönnis grade-3 coxarthrosis, total hip replacement becomes the dominant treatment strategy.

CONCLUSIONS

Periacetabular osteotomy is, on the average, more cost-effective in Tönnis grade-1 and grade-2 coxarthrosis, while it is both more costly and less effective in Tönnis grade-3 coxarthrosis. These findings can inform clinical decision-making in the absence of long-term data. On the basis of this model, periacetabular osteotomy is preferable to total hip arthroplasty in Tönnis grade-1 and grade-2 coxarthrosis when the patient is sufficiently young and when functionality in sports is important.

The need for evolution in healthcare decision modeling

STATEMENT OF PROBLEM

Many healthcare decisions are difficult because they are complex and have important consequences such as the impact on survival or quality-of-life of individuals and on allocation of limited resources. The present state-of-the-art in healthcare decision modeling is often inadequate to properly assess these decisions.

METHODS

Based on a literature search and the experience of the authors, typical methodologies used in healthcare decision analysis modeling are explored and compared with methods used in other practices. An example of hormonal therapy decisions is used.

RESULTS

Useful methods that have been developed in other fields are presented. These include methods targeted toward appropriate assessment and representation of the complexity of decisions, assessment of uncertainty, use of nonexpected value decision analysis, and use of multi-attribute decision criteria.

CONCLUSION

The state-of-the-art in healthcare decision modeling can be improved through learning from other practices.

Utility assessment in cancer patients: adjustment of time tradeoff scores for the utility of life years and comparison with standard gamble scores

The standard gamble (SG) and the time tradeoff (TTO), two frequently used methods of utility assessment, have often been found to lead to different utilities for the same health state. The authors investigated whether adjustment of TTO scores for the utility of life years (risk attitude) eliminated this difference. In addition, the association between risk attitude and sociodemographic and medical variables was studied. In 30 disease-free testicular cancer patients, SG and TTO were used to assess the utilities of four health profiles relevant to testicular cancer. Utility of life years was estimated from certainty equivalents (CEs). SG scores were significantly higher than unadjusted TTO scores for all profiles. As the majority of patients (85%) were risk-averse, CE-adjusted TTO scores were higher than unadjusted scores, and were not significantly different from those obtained from the SG for three of the four profiles. However, adjusted scores were still slightly but consistently lower than SG scores. Possible explanations for this discrepancy are discussed. An association was found between risk aversion and medical treatment: patients who had received chemotherapy for their cancers were more risk-averse than were patients who had been in a surveillance protocol only. As risk aversion can have an impact on treatment decisions, it is important to assess the risk posture of the patient to whom the decision pertains.