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In order to know whether the data has been adapter-trimmed for microRNA data, we can look at the pre-alignment QA/QC of the raw data, specifically the read length distribution. If the read length distribution peaks at approximately 22-23 bases, this usually means the data has been adapter-trimmed. However, if you have a fixed length distribution, then very likely the data is not adapter-trimmed and you will need to get the adapter sequence from your vendor or service provider and use the Trim adapter function to trim away the adapter sequence.

 
Partek Flow software ^® Flow^® software wraps Cutadapt [1], a widely used tool for adapter trimming. It can be used to trim adapter sequences in nucleotide-space data as well as color-space data.

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