<p>You can simply replace the sequence and quality scores with a single <code>*</code> in each field. The CIGAR information will still be there, so it will be apparent where there were InDels and possibly mismatches (assuming your aligning uses <code>=</code> and <code>X</code> CIGAR operations), but since the actual sequence of these variants cannot be known this is quite anonymized.</p>

CC BY-SA 4.0
2020-06-19T21:53:05.560Z
2020-06-19T21:53:05.560Z
Devon Ryan
<p>I have a bam file of, for instance, RNA-Seq, which contains patient-identifiable data in the form of Single Nucleotide Polymorphisms (SNPs) throughout.</p>
<p>I would like a technique to take this aligned bam file and replace all the non-reference bases with the reference bases at the equivalent positions (hard-clipping any soft-clipped bases while doing so), in order to have an anonymised bam file without the patient-identifiable information.</p>
<p>What is the best way to do this? I want the resulting anonymised bam file to have the reads in the same positions, for downstream tools that care about the alignment positions.</p>

CC BY-SA 4.0
2020-06-19T20:51:28.883Z
Hi @KraZug normally patient confidentiality is maintained through anonminity of name and personal information, but not to anonymize the DNA by ad hoc editting. No ethics committee would request that. Personally, I don't agree here.
M__
CC BY-SA 4.0
2020-06-19T21:49:07.600Z
In the event of a publication, normally you can submit to ega or dbgap https://www.ncbi.nlm.nih.gov/gap/docs/submissionguide/#:~:text=To%20comply%20with%20HIPAA%2C%20personally,submitted%20in%20dbGaP%20data%20files. and they have a set of guidelines on how u de-identify samples
StupidWolf
<sam><ngs>
How to anonymise a bam file
# How to anonymise a bam file

(Asked by: username_0 on 2020-06-19)

I have a bam file of, for instance, RNA-Seq, which contains patient-identifiable data in the form of Single Nucleotide Polymorphisms (SNPs) throughout.

I would like a technique to take this aligned bam file and replace all the non-reference bases with the reference bases at the equivalent positions (hard-clipping any soft-clipped bases while doing so), in order to have an anonymised bam file without the patient-identifiable information.

What is the best way to do this? I want the resulting anonymised bam file to have the reads in the same positions, for downstream tools that care about the alignment positions.

**Tags:** sam, ngs
> **Comments:**
> **username_1**: Hi @KraZug normally patient confidentiality is maintained through anonminity of name and personal information, but not to anonymize the DNA by ad hoc editting. No ethics committee would request that. Personally, I don't agree here.  
> **username_2**: In the event of a publication, normally you can submit to ega or dbgap https://www.ncbi.nlm.nih.gov/gap/docs/submissionguide/#:~:text=To%20comply%20with%20HIPAA%2C%20personally,submitted%20in%20dbGaP%20data%20files. and they have a set of guidelines on how u de-identify samples  

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## 1 answers

### Answer by username_3 on 2020-06-19. Score: 1

You can simply replace the sequence and quality scores with a single `*` in each field. The CIGAR information will still be there, so it will be apparent where there were InDels and possibly mismatches (assuming your aligning uses `=` and `X` CIGAR operations), but since the actual sequence of these variants cannot be known this is quite anonymized.


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