Bioinformatics Advance Access originally published online on October 10, 2005
Bioinformatics 2005 21(23):4272-4279; doi:10.1093/bioinformatics/bti708
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The influence of missing value imputation on detection of differentially expressed genes from microarray data
1Department of Mathematics, University of Oslo PO Box 1053, Blindern, NO-0316 Oslo, Norway
2Department of Statistical Analysis, Image Analysis and Pattern Recognition, Norwegian Computing Center NO-0314 Oslo, Norway
3Department of Radiation Biology, The Norwegian Radium Hospital NO-0310 Oslo, Norway
4Department of Biostatistics, University of Oslo NO-0317 Oslo, Norway
*To whom correspondence should be addressed.
Motivation: Missing values are problematic for the analysis of microarray data. Imputation methods have been compared in terms of the similarity between imputed and true values in simulation experiments and not of their influence on the final analysis. The focus has been on missing at random, while entries are missing also not at random.
Results: We investigate the influence of imputation on the detection of differentially expressed genes from cDNA microarray data. We apply ANOVA for microarrays and SAM and look to the differentially expressed genes that are lost because of imputation. We show that this new measure provides useful information that the traditional root mean squared error cannot capture. We also show that the type of missingness matters: imputing 5% missing not at random has the same effect as imputing 1030% missing at random. We propose a new method for imputation (LinImp), fitting a simple linear model for each channel separately, and compare it with the widely used KNNimpute method. For 10% missing at random, KNNimpute leads to twice as many lost differentially expressed genes as LinImp.
Availability: The R package for LinImp is available at http://folk.uio.no/idasch/imp
Contact: idasch{at}math.uio.no
Supplementary information: http://folk.uio.no/idasch/imp
Received on June 9, 2005; revised on September 20, 2005; accepted on October 5, 2005
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