p-value<0.05 for a gene with zero counts?
1
0
Entering edit mode
@andrebolerbarros-16788
Last seen 6 months ago
Portugal

Hi everyone,

I was performing a comparison using DESeq2. Considering it is relevant for the case, I used a code I found here (DESeq2 baseMean values for each sample) to find the mean counts for each condition.

So, looking at a gene where both groups have zero counts, I obtained a significant p-value (quite small even, 5.7E-6). Since I had a warning about convergence, I also checked and it did converge.

Is this possible? I understand that the independentFiltering maintains the gene, since it has reads for other conditions but, considering the counts, it should be at least non-significant no?

The code is rather straightforward:

baseMeanPerLvl <- sapply( levels(dds_sub$CellType), function(lvl) 
      rowMeans(counts(dds_sub,normalized=TRUE)[,dds_sub$CellType == lvl, drop=F] ) )

resultsNames(dds_sub)
res1<-results(dds_sub,name =  "CellType_Neutrophils_vs_Eosinophil", alpha = 0.05)
res1<-lfcShrink(dds_sub,coef = "CellType_Neutrophils_vs_Eosinophil", type = "apeglm",res = res1)

Thanks in advance

DESeq2 • 730 views
ADD COMMENT
0
Entering edit mode
@mikelove
Last seen 4 days ago
United States

Can you use contrast instead of name? This should resolve it.

ADD COMMENT
0
Entering edit mode

It indeed solved the problem, now the genes in question get a p-value of 1 and log2FC. However, what does this means for lfcshrink, should I keep the usage of coef for apeglm?

ADD REPLY
0
Entering edit mode

Yes, you can keep use of coef in apeglm.

And note that in apeglm you can specify svalue=TRUE or an lfcThreshold even if you want to find a set of genes with large posterior LFC.

ADD REPLY

Login before adding your answer.

Traffic: 610 users visited in the last hour
Help About
FAQ
Access RSS
API
Stats

Use of this site constitutes acceptance of our User Agreement and Privacy Policy.

Powered by the version 2.3.6