Hello,

If I have TPM values for gene A from the UCSC database which contains multiple isoforms, and lets say I want just 1 output for gene A, can I average or add the TPM values?  

If I can't do that is it possible to go back to the raw reads and add them at the raw read level?

I just want to condense genes for my dataset.
If they are calculated correctly (e.g. with RSEM or similar), the quantification should be divided among the isoforms in a mutually exclusive way. 

So if you have 

Isoform1 3 TPM  - three transcripts
Isoform2 1 TPM - one transcript

The total gene should have 4 transcripts per million (i.e. 4 independent transcripts, 3 from Isoform1 and one from Isoform2.)