Conclusions The last 10 years has seen a substantial increase in the number of mapping studies and some evidence of advancement in methods with consideration of models beyond OLS and greater reporting of predictive ability of mapping functions
Background Mapping is an increasingly common method used to predict instrument-specific preference-based health-state utility values ( HSUVs ) from data obtained from another health-related quality of life ( HRQoL ) measure .
There have been several method ological developments in this area since a previous review up to 2007 .
Use of a disease-specific instrument in economic evaluations: mapping WOMAC onto the EQ-5D utility index.
OBJECTIVE To map the Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) onto the EuroQol 5 Dimension ( EQ-5D ) utility index in patients with knee osteoarthritis ( OA ) . METHODS A consecutive sample of patients ( n=258 ) diagnosed with knee OA completed both the WOMAC and the EQ-5D . Regression models with the ordinary least squares ( OLS ) or the censored least absolute deviations as the estimator were used to establish the mapping function . The WOMAC was represented as explanatory variables in four ways : 1 ) total score ; 2 ) domain scores ( i.e. , pain , stiffness , and physical function ) ; 3 ) domain scores plus pair-wise interaction terms to account for possible nonlinearities ; and 4 ) individual item scores . Goodness-of-fit criteria included the mean absolute error ( the primary criterion ) and the root mean squared error , and were obtained using an iterative r and om sampling procedure . Prediction precision was evaluated at individual patient level and at the group level . RESULTS The model using the OLS estimator and the WOMAC domain scores as explanatory variables had the best fit and was chosen as the preferred mapping model . The prediction error at the individual level exceeded the maximal tolerance value ( i.e. , the minimally important difference of the EQ-5D ) in about 16 % of the patients . At the group level , the width of the 95 % confidence interval of prediction errors varied from 0.0176 at a sample size of 400 to 0.0359 at a sample size of 100 . CONCLUSIONS EQ-5D scores can be predicted using WOMAC domain scores with an acceptable precision at both individual and group levels in patients with mild to moderate knee OA
Conclusions The last 10 years has seen a substantial increase in the number of mapping studies and some evidence of advancement in methods with consideration of models beyond OLS and greater reporting of predictive ability of mapping functions
Background Mapping is an increasingly common method used to predict instrument-specific preference-based health-state utility values ( HSUVs ) from data obtained from another health-related quality of life ( HRQoL ) measure .
There have been several method ological developments in this area since a previous review up to 2007 .