The development of smoothing-independent kinematic measures of capacitating human sperm movement

The kinematic values which are determined relative to the average path by computer-aided sperm analysis (CASA) instruments are reliant upon the algorithm used for track smoothing, and thereforemay differ depending upon the shape and complexity of the trajectories analysed. To overcome this potential source of error in the identification of particular trajectory patterns, kinematic values must be derived so that they are independent of the average path. In this study a number of novel kinematic measures were developed and tested for their ability to differentiate between hyperactivated and non-hyperactivated human spermatozoa. A definition for hyperactivation which relied solely upon smoothing-independent kinematic values was developed. This definition was tested on two groups of trajectories reconstructed at 60 Hz by a CASA instrument. An overall agreement of 99% between the classification of tracks as hyperactivated or non-hyperactivated was observed between the established 60 Hz definition validated for that particular CASA instrument and the new, smoothing-independent definition. Because the new values are only reliant upon (x,y) coordinates for their calculation, and do not require smoothing, it should not be difficult to incorporate them into existing CASA instruments.