Are decisions using cost-utility analyses robust to choice of SF-36/SF-12 preference-based algorithm?
BACKGROUND
Cost utility analysis (CUA) using SF-36/SF-12 data has been facilitated by the development of several preference-based algorithms. The purpose of this study was to illustrate how decision-making could be affected by the choice of preference-based algorithms for the SF-36 and SF-12, and provide some guidance on selecting an appropriate algorithm.


METHODS
Two sets of data were used: (1) a clinical trial of adult asthma patients; and (2) a longitudinal study of post-stroke patients. Incremental costs were assumed to be 2000 dollars per year over standard treatment, and QALY gains realized over a 1-year period. Ten published algorithms were identified, denoted by first author: Brazier (SF-36), Brazier (SF-12), Shmueli, Fryback, Lundberg, Nichol, Franks (3 algorithms), and Lawrence. Incremental cost-utility ratios (ICURs) for each algorithm, stated in dollars per quality-adjusted life year (dollars/QALY), were ranked and compared between datasets.


RESULTS
In the asthma patients, estimated ICURs ranged from Lawrence's SF-12 algorithm at 30,769 dollars/QALY (95% CI: 26,316 to 36,697) to Brazier's SF-36 algorithm at 63,492 dollars/QALY (95% CI: 48,780 to 83,333). ICURs for the stroke cohort varied slightly more dramatically. The MEPS-based algorithm by Franks et al. provided the lowest ICUR at 27,972 dollars/QALY (95% CI: 20,942 to 41,667). The Fryback and Shmueli algorithms provided ICURs that were greater than 50,000 dollars/QALY and did not have confidence intervals that overlapped with most of the other algorithms. The ICUR-based ranking of algorithms was strongly correlated between the asthma and stroke datasets (r = 0.60).


CONCLUSIONS
SF-36/SF-12 preference-based algorithms produced a wide range of ICURs that could potentially lead to different reimbursement decisions. Brazier's SF-36 and SF-12 algorithms have a strong methodological and theoretical basis and tended to generate relatively higher ICUR estimates, considerations that support a preference for these algorithms over the alternatives. The "second-generation" algorithms developed from scores mapped from other indirect preference-based measures tended to generate lower ICURs that would promote greater adoption of new technology. There remains a need for an SF-36/SF-12 preference-based algorithm based on the US general population that has strong theoretical and methodological foundations.
Pickard
A Simon
AS
Center for Pharmacoeconomic Research, College of Pharmacy, Room 164, 833 S, Wood St (MC886), University of Illinois at Chicago, 60612, USA. pickard1@uic.edu
Wang
Zhixiao
Z
Walton
Surrey M
SM
Lee
Todd A
TA
D000328:Adult; D000368:Aged; D000465:Algorithms; D001249:Asthma / Q000191:economics / Q000503:physiopathology; D002986:Clinical Trials as Topic; D003362:Cost-Benefit Analysis / Q000379:methods*; D003663:Decision Trees; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000191:economics / Q000379:methods*; D017060:Patient Satisfaction; D011594:Psychometrics; D019057:Quality-Adjusted Life Years; D018434:Sickness Impact Profile; D020521:Stroke / Q000191:economics / Q000503:physiopathology; D014481:United States