# PETRO

Perturb-seq often pools several guides per target as replicates, but a guide's off-target effects can bias the target-level estimate. PETRO assumes a strict majority of guides are valid for each outcome and uses robust weighting to downweight disagreeing guides, recovering the on-target perturbation effect without removing guides or using sequence annotations. In RPE-1 CRISPRa target-outcome pairs whose longest seed match was 13–18 bp, mean pooled bias was 0.087 and PETRO's residual bias was 0.005; in simulation, pooling stayed near 0.075 as cells increased while PETRO fell toward zero.

Perturb-seq often pools several guides per target as replicates, but a guide's off-target effects can bias the target-level estimate. PETRO assumes a strict majority of guides are valid for each outcome and uses robust weighting to downweight disagreeing guides, recovering the on-target perturbation effect without removing guides or using sequence annotations. In RPE-1 CRISPRa target-outcome pairs whose longest seed match was 13–18 bp, mean pooled bias was 0.087 and PETRO's residual bias was 0.005; in simulation, pooling stayed near 0.075 as cells increased while PETRO fell toward zero.