Motivation
In RNA-seq differential expression analysis, investigators aim to detect those genes with changes in expression level across conditions, despite technical and biological variability in the observations. A common task is to accurately estimate the effect size, often in terms of a logarithmic fold change (LFC).
Results
When the read counts are low or highly variable, the maximum likelihood estimates for the LFCs has high variance, leading to large estimates not representative of true differences, and poor ranking of genes by effect size. One approach is to introduce filtering thresholds and pseudocounts to exclude or moderate estimated LFCs. Filtering may result in a loss of genes from the analysis with true differences in expression, while pseudocounts provide a limited solution that must be adapted per dataset. Here, we propose the use of a heavy-tailed Cauchy prior distribution for effect sizes, which avoids the use of filter thresholds or pseudocounts. The proposed method, Approximate Posterior Estimation for generalized linear model,
apeglm
, has lower bias than previously proposed shrinkage estimators, while still reducing variance for those genes with little information for statistical inference.
Availability and implementation
The
apeglm
package is available as an R/Bioconductor package at
https://bioconductor.org/packages/apeglm
, and the methods can be called from within the
DESeq2
software.
Supplementary information
Supplementary data
are available at
Bioinformatics
online.
The results of the intergroup E1690 trial demonstrate an RFS benefit of IFNalpha2b that is dose-dependent and significant for HDI by Cox multivariable analysis.
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