DESeq-statistical analysis without replicate

[lynn012]

Dear all,
I don't have any replicate for my samples,and When I run the minimal set of commands:
> cds <- newCountDataSet( countsTable, conds )
> cds <- estimateSizeFactors( cds )
> cds <- estimateVarianceFunctions( cds, method="blind")
> res <- nbinomTest( cds, "A", "B")
Error: condA %in% levels(conditions(cds)) is not TRUE
what's the problem?

Thanks for your answers