Objective To analyze the detection ability of survival motor neuron(SMN)gene deletion of exons in clinical laboratories in Shanghai using external quality assessment(EQA).Methods Genomic DNA from the cell lines containing different SMN exon copy numbers were selected as EQA samples.The EQA sample panel,which consisted of 5 samples,was randomly selected twice and distributed to participating laboratories in Shanghai in 2023.The seresults were required to be conducted and uploaded within the specified time.Based on the reported results,statistical analysis was performed and the detection ability was evaluated.Results In the two EQA,laboratory that submitted all correct results for SMN1 accounted for 100%(38/38)and 97.22%(35/36),respectively.The overall coincidence rates were 96.92%(315/325)and 98.18%(324/330)for copy number detection of SMN1 exon 7 and 8,100%(65/65)and 96.56%(43/45)for copy number detection of SMN2 exon 7 and 8.The reported error results included case of result judgment error and 4 cases of copy number detection errors.Conclusion Screening genomic DNA from the cell lines containing different SMN exon copy numbers can effectively simulate the clinical samples,which can be applied to EQA material for deletion of exons in the SMN gene.The reported results show that the overall compliance rate of SMN deletion of exons in clinical laboratories in Shanghai is relatively high,but the testing capabilities of some laboratories still need to be improved.