Application of the upgraded image superimposition system (SIAS) to the assessment of sperm kinematics.

Dedicated software for semiautomatic objective motility assessment, based on image superimposition (SIAS), was upgraded in order to allow automatic reading of sperm tracks whilst keeping the advantages of visual check instead of the digital images of classic computer-aided sperm analysis (CASA) systems. The new system is very fast and accurate and allows an excellent reading of sperm motility in standard semen analysis. Moreover, using this system, an attempt was made to define numerically straight-line velocity (VSL), curvilinear velocity (VCL) and linearity (LIN) in each WHO sperm motility class. At 21 frames sec-1, ROC curves analysis determined the following: Class 1 (typical of WHO grade 'a'): VSL > or = 23 microns sec-1 and LIN > or = 0.58; class 2 (typical of WHO grade 'b'): VSL > 10 and < 23 microns sec-1 and LIN > or = 0.58; class 3: VSL > 10 microns sec-1 and LIN < 0.58 (this additional class was added to differentiate nonstraight progressive motility from classes 1 and 2); class 4 (typical of WHO grade 'c'): VSL < or = 10 microns sec-1. The numerical definition of sperm motility classes may contribute towards standardization in the objective evaluation of sperm kinematics.