Re: normalization and batch correction across multiple project

Dear all,

I had no response to this email that I sent last week. If anyone has any
input, I would greatly appreciate it. Thank you.

Regards, Adai


On Mon, Aug 18, 2014 at 1:11 PM, Adaikalavan Ramasamy <
[email protected]> wrote:

> Dear all,
>
> I would like to appeal to the collective wisdom in this group on how best
> to solve this problem of normalization and batch correction.
>
> We are a service unit for an academic institute and we run several
> projects simultaneously. We use Illumina HT12-v4 microarrays which can
> take up to 12 different samples per chip. As we QC the data from one
> project, the RNA from failed samples can be repeated to include into chips
> from another project (rather than running partial chips to avoid wastage).
> Sometimes we include samples from other projects also. Here is a simple
> illustration
>
> Chip No       ScanDate    Contents
> 1                1st July        *12 samples from project A*
> 2                1st July          *8 samples from project A* + 4 from
> project B
> 3                1st August   12 samples from Project B
> 4                1st August     *1 sample from Project A* + 5 samples
> from B + 6 from project C
> ...
>
> What is the best way to prepare the final data for *project A*? One
> option is to do the following:
>
>    1. Pool chips 1, 2 and 4 together.
>    2. Remove failed samples
>    3. Remove samples from other projects.
>    4. Normalize using NEQC from limma
>    5. Correct for scan date using COMBAT from sva.
>
> The other option we considered is to omit step 3 (i.e. use other samples
> for normalization and COMBAT) and subset at the end.
>
> I feel this second option allows for better estimation of batch effects
> (especially in chip 4). However, sometimes project A and B can be quite
> different (e.g. samples derived from different tissues) which might mess up
> the normalization especially if we want to compare project A to B directly. We
> also considered nec() followed by normalizeBetweenArrays with "Tquantile"
> but I felt it was too complicated. Anything else to try?
>
> Thank you.
>
> --
>
> Adaikalavan Ramasamy
>
> Senior Leadership Fellow in Bioinformatics
>
> Head of the Transcriptomics Core Facility
>
>
>
> Email: [email protected]
>
> Office: 01865 287 710
>
> Mob: 07906 308 465
>
> http://www.jenner.ac.uk/transcriptomics-facility
>
>
>
>
>
>
>

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