# Guide RNA Calling

DRAGEN now also supports guide RNA calling - identifying cells that express guide RNA sequences. Although the counts matrix reports how many feature counts were found for each cell, there is a chance that the feature reads happened to match to the feature barcode reference sequence or the feature count was assigned to the cell by chance rather than due to real signal. Guide RNA calling applies an additional filtering step to distinguish between cells truly expressing guide RNA sequences and noise (similar to how cell filtering is performed to distinguish true passing cells from noise)

For more information on Guide RNA calling refer to the [DRAGEN documentation](https://help.dragen.illumina.com/product-guide/dragen-v4.4/dragen-single-cell-pipeline/dragen-scrna-pipseq#pipseq-crispr-mode) detailing the Gaussian Mixture Model approach.