Health-State Utility Values in CP Patients Following Deformity Surgery: Are We Now Ready for Cost-Utility Analysis in This Patient Population?

Background

Cost-utility analysis (CUA) is frequently used by reimbursement agencies and national advisory bodies to make informed decisions on whether or not to reimburse surgical interventions. Health state preferences (utilities) are a key component in valuing health outcomes in that they are used in calculating quality-adjusted life-years (QALY). Unfortunately, disease-specific HRQoL measures commonly lack the preference weights necessary to produce health-state utility values for use in CUA. A solution to this problem is to map a disease-specific quality-of-life measure to a generic preference-based measure. The aim of this study was to develop health-state utility values for cerebral palsy (CP) patients with scoliosis by mapping disease-specific quality-of-life scores (CPCHILD outcome questionnaire) to the Health Utility Index Mark 3 (HUI3) questionnaire.

Methods

A prospective, multicentre CP scoliosis database was analysed identifying consecutive CP patients with ≥2 years follow-up who completed both the CPCHILD and HUI3 at enrolment, at 1-, and at 2 years follow-up. Ordinary least squared regression models were constructed to estimate HUI3 utility values from CPCHILD scores and clinical variables. The model was developed using enrolment data, while 1- and 2-years follow-up data were used for confirmatory analysis of the goodness of fit of the model (i.e., paired t test between observed and calculated HUI utility values).

Results

A total of 232 patients were included, 91.9% were GMFCS IV and V, 87.9% underwent surgery during the study period, and the average magnitude of scoliosis deformity at enrolment was 81.93° ± 25.13°. A log-linear regression model was developed, including three predicting variables: CPCHILD total score (β = 0.016, p = 0.0001), communication (β = -0.436, p = 0.0001), and feeding ability (β = -0.289, p = 0.0001). The R2 of the model was 0.578, and F 49.73 (p = 0.0001). The mean difference of means between observed HUI3 values and calculated HUI3 values at 1- and 2 years was -0.020 (p = 0.129) and 0.017 points (p = 0.187), respectively.

Conclusions

Although the use of a preference-based HRQoL measure is the ideal method to generate health-state utility values, we demonstrate that HUI3 scores can be accurately predicted using the CPCHILD questionnaire. This mapping algorithm will be useful in estimating health-state utilities in clinical trials, and hence CUA, of CP patients undergoing scoliosis surgery to help better inform patients, care-givers, health-care providers, and decision makers of the economic burden of surgery in this patient population.