This study evaluated technicians’ ability to identify sperm morphology via external quality assessment (EQA) and identified challenging defect types causing significant interparticipant discrepancies. A longitudinal study was conducted from 2019 to 2024 to assess the ability of technicians at various laboratories to identify sperm morphology using standardized EQA protocols and distributed sperm images. Morphological classification was performed using the criteria of the World Health Organization, 6th edition. Correct identification rates, participant pass rates, and defect-specific accuracy rates were statistically analyzed. The overall correct identification rate (mean ± standard deviation [s.d.]) was 81.3% ± 27.0%, while the correct identification rate of normal sperm morphology (mean ± s.d.) was only 51.1% ± 25.5%. Although the overall correct identification rate of abnormal sperm morphology (mean ± s.d.) was as high as 96.1% ± 8.9%, the overall correct identification rate across all defect categories (mean ± s.d.) was only 60.2% ± 21.7%. The identification of sperm head defects was the most challenging, with a correct identification rate (mean ± s.d.) of only 57.0% ± 20.7%, while the correct identification rate of sperm tail defects (mean ± s.d.) was the highest at 70.5% ± 23.5%. Among sperm head defects, the correct identification rate of head size defects (mean ± s.d.) was the lowest at 53.4% ± 22.0%. Laboratories that participated for 5 consecutive years showed significant improvements in total and normal morphology scores. Image-based EQA effectively assesses the technicians’ competency and serves as an educational tool. Normal sperm morphology evaluation should avoid overly strict criteria, while abnormal sperm morphology assessment requires enhanced focus on specific defect types.

Keywords: defect identification; external quality assessment; male infertility; sperm morphology; technicians’ ability

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