Does the missing data imputation method affect the composition and performance of prognostic models?
BACKGROUND
We already showed the superiority of imputation of missing data (via Multivariable Imputation via Chained Equations (MICE) method) over exclusion of them; however, the methodology of MICE is complicated. Furthermore, easier imputation methods are available. The aim of this study was to compare them in terms of model composition and performance.


METHODS
Three hundreds and ten breast cancer patients were recruited. Four approaches were applied to impute missing data. First we adopted an ad hoc method in which missing data for each variable was replaced by the median of observed values. Then 3 likelihood-based approaches were used. In the regression imputation, a regression model compared the variable with missing data to the rest of the variables. The regression equation was used to fill the missing data. The Expectation Maximum (E-M) algorithm was implemented in which missing data and regression parameters were estimated iteratively until convergence of regression parameters. Finally, the MICE method was applied. Models developed were compared in terms of variables significantly contributed to the multifactorial analysis, sensitivity and specificity.


RESULTS
All candidate variables significantly contributed to the MICE model. However, grade of disease lost its effect in other three models. The MICE model showed the best performance followed by E-M model.


CONCLUSIONS
Among imputation methods, final models were not the same, in terms of composition and perform-ance. Therefore, modern imputation methods are recommended to recover the information.
Research Center for Modelling in Health, Kerman University of Medical Sciences, Kerman, Iran.
M R
MR
Baneshi
A R
AR
Talei