P-038 Sperm head morphometric reference values of 1856 sperms in fertile Asian males
Authors: Jia Y , Li F , Zhang L 
Published: July 2024

Abstract

Study question
To explore comprehensive normal sperm morphometric reference values by measuring 1856 sperms in fertile males using artificial intelligence (AI) technique.

Summary answer
Four novel describing parameters of sperm head (size, shape, area, and uniformity) and 14 other features for normal sperm head were extracted and characterized.

What is known already
Sperm head morphology is crucial for male factor infertility diagnosis and assessment of male reproductive potential. The human spermatozoon is one of the most diverse cell types known. However, most assessment criteria have only 3 morphometric parameters (Length, width, and length/width ratio) for sperm head morphometric measurement. We detailed the features of sperm head by defining and characterizing 14 parameters based on AI.

Study design, size, duration
This is a prospective observational study. The study included 1856 normal sperm images from 23152 stained sperm acquired by an Automated Sperm Morphology Analysis (ASMA) system. The measured sperm morphometry data were acquired from May 2020 to December 2021.

Participants/materials, setting, methods
All participants (54 fertile males) had fathered a child naturally during the past year. The measured sperm morphometry data were acquired from candidate donors of the Sichuan Province Human Sperm Bank (SPHSB, Chengdu, China). Images of 23,152 stained sperm captured by ASMA. All sperm images were assessed by three experienced technicians. Finally, we concluded 14 morphometric data from normal sperm by measuring sizes in pixels.

Main results and the role of chance
(1) Characteristics of sperm head size and shape: We present eight sperm head size and shape parameters for the 1856 visually normal spermatozoa. The median head size parameters included head length of 4.02 (95% CI: 4.01–4.05) μm, head width of 2.52 (95% CI: 2.52–2.54) μm, length to width ratio of 1.59 (95% CI: 1.59–1.62), and head girth of 11.18 (95% CI: 11.17–11.25) μm. The median head symmetry parameters included short axis symmetry (SAS) of 92.1% (95% CI: 88.3%–89.2%) and the long axis symmetry (LAS) of 94.3% (95% CI: 91.6%–92.3%). The median head shape parameters included median of ellipse intersection over union (EIoU) of 88.9% (95% CI: 85.4%–86.3%) and girth intersection over union (GIoU) of 102.4% (95% CI: 102.4%–102.5%).
(2) Characteristics of sperm head area and acrosome uniformity: Descriptive analysis of the sperm head area characteristics included a median sperm head area of 7.72 (95% CI: 7.74–7.85) μm2, acrosome area of 3.67 (95% CI: 3.77–3.88) μm2, acrosome area ratio of 48.2% (95% CI: 47.8%–48.6%), post-acrosomal area of 3.95 (95% CI: 3.95–4.00) μm2, acrosome uniformity of 88.6% (95% CI: 88.6%–89.1%), and nuclear uniformity of 100.0% (95% CI: 99.8%–99.9%).

Limitations, reasons for caution
This study had several limitations that should be noted. The use of samples from a single center, covering relatively young participants from only seven provinces in China, could limit the usage of our findings. The use of only three technicians to assess the samples may have introduced a subjective bias.

Wider implications of the findings
The measurement technique was accurate, objective, and highly informative by AI. The data provide extremely detailed information for reference studies and comparison of sperm head parameters among different male groups. These new parameters can be applied in routine semen analysis when assessing sperm morphology and male fertility potential.

Trial registration number
not applicable