[BioC] How does one deal with spatial effects detected on single channel microarrays?

[cstrato]

Dear Scott,

Yes and yes, however even the crop circles may be ok. There are a lot of 
quality controls that you can do additionally, e.g. PCA, NUSE, RLE, 
border plots, center of intensity plots, etc.

Best regards,
Christian


On 9/2/13 6:41 PM, Scott Robinson wrote:
> Dear Christian,
>
> Thanks very much for the help. I especially like the "crop circles" artefact.
>
> So is the idea that if you have a small spatial artefact it's probably going to affect only a small number of the probes in each probe set and therefore not affect the summarised values much? Do you only have to spatially normalize or remove a chip from analysis if the spatial artefact is quite large? Maybe if it covers 1/4 of the chip or something?
>
> Thanks,
>
> Scott
>
> -----Original Message-----
> From: cstrato [mailto:cstrato at aon.at]
> Sent: 02 September 2013 16:28
> To: Scott Robinson [guest]
> Cc: bioconductor at r-project.org; Scott Robinson
> Subject: Re: [BioC] How does one deal with spatial effects detected on single channel microarrays?
>
> Dear Scott,
>
> Unlike cDNA arrays Affymetrix arrays use between 11 and 20 oligonucleotides per transcript. These oligos were placed in one line on the first Hu6800 array, but since a long time these oligos are scattered randomly across the whole array, in order to prevent spatial effects.
>
> The images of your arrays are all ok.
> You can see some weird examples at:
> http://plmimagegallery.bmbolstad.com/
>
> Best regards
> Christian
> _._._._._._._._._._._._._._._._._._
> C.h.r.i.s.t.i.a.n   S.t.r.a.t.o.w.a
> V.i.e.n.n.a           A.u.s.t.r.i.a
> e.m.a.i.l:        cstrato at aon.at
> _._._._._._._._._._._._._._._._._._
>
>
>
> On 9/2/13 2:44 PM, Scott Robinson [guest] wrote:
>>
>> Dear all,
>>
>> I have been doing pre-processing & QC of a number of CEL files (from Affymetrix U133+ v2.0 chips), basing things loosely on this tutorial (http://bioinformatics.knowledgeblog.org/2011/06/20/analysing-microarray-data-in-bioconductor/), and on some past experience of other microarray technologies.
>>
>> Many tutorials seem to deal with indentification of spatial effects but do not discuss how to handle them. As such I have been having difficulty finding methods directed at spatial normalization in single-channel arrays (OLIN, smida, marray and nnNorm all seem to be written for dual-channel arrays). Can anyone please suggest an appropriate package/method for single-channel Affy chips?
>>
>> And are there cases where they should be excluded rather than normalized?
>>
>> Some examples of my spatial artefacts:
>>
>> http://postimg.org/image/kkfjt4o1j/
>> http://postimg.org/image/v5utre4zb/
>> http://postimg.org/image/yfdublign/
>>
>> Of my 90 chips example 2 is the only one of that kind of pattern. The rest are mostly similar in form to the other 2 and similar patterns are seen in ~20 chips.
>>
>> Thanks in advance,
>>
>> Scott
>>
>>    -- output of sessionInfo():
>>
>> R version 3.0.1 (2013-05-16)
>> Platform: x86_64-w64-mingw32/x64 (64-bit)
>>
>> locale:
>> [1] LC_COLLATE=English_United Kingdom.1252 [2] LC_CTYPE=English_United
>> Kingdom.1252 [3] LC_MONETARY=English_United Kingdom.1252 [4]
>> LC_NUMERIC=C [5] LC_TIME=English_United Kingdom.1252
>>
>> attached base packages:
>> [1] parallel  stats     graphics  grDevices utils     datasets  methods
>> [8] base
>>
>> other attached packages:
>>    [1] limma_3.16.7          sparcl_1.0.3          lattice_0.20-23
>>    [4] corrplot_0.71         affyPLM_1.36.0        preprocessCore_1.22.0
>>    [7] simpleaffy_2.36.1     gcrma_2.32.0          genefilter_1.42.0
>> [10] affy_1.38.1           Biobase_2.20.1        BiocGenerics_0.6.0
>>
>> loaded via a namespace (and not attached):
>>    [1] affyio_1.28.0        annotate_1.38.0      AnnotationDbi_1.22.6
>>    [4] BiocInstaller_1.10.3 Biostrings_2.28.0    DBI_0.2-7
>>    [7] grid_3.0.1           IRanges_1.18.3       RSQLite_0.11.4
>> [10] splines_3.0.1        stats4_3.0.1         survival_2.37-4
>> [13] XML_3.98-1.1         xtable_1.7-1         zlibbioc_1.6.0
>>
>> --
>> Sent via the guest posting facility at bioconductor.org.
>>
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>