Providing an extended use of an otological-specific outcome instrument to derive cost-effectiveness estimates of treatment.

ABSTRACT

OBJECTIVES: Although quality-adjusted life years (QALYs) are increasingly being used by decision-makers to make comparisons of cost-effectiveness, there are no otological-specific outcome measures that fit within this QALY framework. This study had two main objectives. The first was to provide a means to derive QALYs from a condition-specific otological instrument (Cambridge Otology Quality of Life, COQOL), and the second was to assess the convergent validity, or degree of correlation, between the COQOL and SF-6D, an established QALY instrument. DESIGN: Longitudinal cohort study designed to assess the convergent validity between SF-6D and COQOL and to generate a mapping function to enable SF-6D values to be predicted from the COQOL responses. SETTING: Cambridge University Hospital, UK. PARTICIPANTS: A total of 207 patients attending a routine outpatient general otology clinic. MAIN OUTCOME MEASURES: SF-6D and the COQOL instrument completed at baseline and again 3 months later. RESULTS: Convergent validity was demonstrated with mean SF-6D values decreasing linearly with increasing severity on the COQOL instrument. Overall, the correlation between the COQOL scores and the SF-6D values was moderate and statistically significant (r = 0.490, P = <0.001). A simple mapping model based on an ordinary least squares (OLS) regression function predicted SF-6D values from the COQOL data with a reasonable degree of accuracy. Further validation using the follow-up 3-month data confirmed the prediction power of this mapping model. CONCLUSIONS: This study provides a method for estimating QALYs from condition-specific COQOL data and provides the opportunity for the cost-effectiveness of otological treatment to be measured and placed within the national QALY framework.