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CASA increases success rate of IVF over manual screening

Dr. Rita Bakshi
Tuesday, December 13, 2016, 08:00 Hrs  [IST]

Computer-assisted sperm analysis (CASA) systems have evolved over 40 years in the history of medical technology, through advances in devices to capture the image of the sperm from a microscope. CASA provides a simple and rapid quantitative assessment of the quality of the sperm and predict its ability to fertilize eggs. It is considered as automatic or semi-automatic technique of semen analysis. CASA helps in analyzing the kinematics of the sperms. This method assesses sperm mobility and concentration on basis of image analysis.

Most major spermatology labs, IVF centres and semen processing facilities have a CASA system. The present CASA technology analysis boar, bull and stallion sperm which requires a different marketed system. CASA can automatically view multiple fields in a shallow specimen chamber to capture strobe-like images of 500 to >2000 sperm, at 50 or 60 frames per second, in <2 minutes, store information for =30 frames and provide summary data for each spermatozoon and the population. CASA also helps in evaluating sperm morphology concurrent with motion. CASA system provides quality assurance of semen and also helps in understanding of the diversity of sperm responses when the system is used skillfully.

Reason behind the need of CASA these days is due to the exposure of various harmful substances present in the environment that accounts adverse health effects they tend to influence on the quality of semen. Hence it is of urgent need to investigate the potential effects of those nanoparticles that may affect the semen quality in human. Several parameters exist to assess male sperm quality. The main methods for assessing sperm quality and sperm motility are through CASA and manual analysis. CASA is an important technique to investigate sperms and nowadays a lot of scientific laboratories use this tool. Although CASA has several advantages as compared to manual analysis, the complex system is susceptible to false negative or positive results when used by an unskilled person. Hence, a thorough validation procedure as well as user training is absolutely necessary in order to profit from this technique. Minimum standards should be defined which should be taken into consideration whenever working with computer-assisted sperm analysis.

In contrast to manual counting, CASA uses hardware and software to visualize and evaluate images of viable sperms to obtain precise and valid information on the kinematics of individual sperms. In manual counting effective use of hemocytometer is highly dependent on accurate pipetting, dilution, and careful calculation, all of which are common sources of error. Whereas CASA gives a detailed objective analysis combined with a high reproducibility, while using identical instrument settings. It considers various parameters like a smoothed path velocity, track velocity, straight line velocity, amplitude of lateral head displacement, or beat cross and it also allows a detailed view into the behavior of individual sperms. Enormous amount of data can be generated from even one single measurement, it gives a detailed view of the mechanism of adverse effects of a substance that effects the sperm motility and quality. CASA is sensitive to small changes in the instrument settings which may lead to a profound change of results. The image acquisition frequency has an impact on the obtained results. An inadequate adjustment of the experimental settings tends to produce false negative or false positive results which may affect the overall outcome of the final study. Temperature control being the most important setting that should be checked since slight reductions in temperature can profoundly affect motility parameters. Another major setting is the illumination and over-exposure whose inappropriate setting can generate false result in the recognition of dust particles and water droplets as static sperms and this can affect the results in a profound way.

CASA is undertaken to analyze the health and viability of a man’s sperm. Factors that tested for in sperm analysis are:

Shape of sperm: A man should have more than 50 per cent of normal shaped sperm. If the result shows that a man has greater than 50 per cent of sperm that are abnormally shaped, this reduces his fertility. Sperm’s head, midsection, or tail is tested in areas of abnormalities. It’s also possible that the sperm could be immature and therefore not able to effectively fertilize an egg.

Number of sperm: Normally sperm count or the sperm density should be between 20 million to over 200 million. If this number is low, conceiving can be more difficult.

Movement of sperm - 'sperm motility': Sperm kinematics is important to fertility because sperm must travel normally to fertilize an egg. An automated system analyzes the sperm for its motility and rates them on a scale of 0 to 4. A score of 0 means the sperm are not moving and a score of 3 or 4 represents good movement.

Liquefaction: Doctors while analyzing semen they test its ability to liquefy or turn to a water consistency that helps the sperm to move. If the sperm doesn’t liquefy or turn into a water consistency within 15-30 minutes, fertility is affected.

The CASA analysis can be done by collecting the semen specimen into a sterile cup. The sperm can be collected by using special condoms during the intercourse or by masturbation. Thereafter the collected sperm sample is evaluated through an imaging system referred to as CASA. The technique reviews the following sperm parameters:

  • Overall Kinematics - Percent of sperm showing any movement.
  • Linear Motility - Percent of sperm moving in a straight line path
  • Rapid Movements - Percent of sperm traveling at a speed of 25um/sec or faster
  • Progressive Motility - Percent of sperm moving rapidly and in a straight path
  • Lateral head displacement - The distance that sperm head back and forth while moving.
  • Mean velocities - An average speed for all sperm in the field of view.
Generally doctors suggest for a semen analysis to those couples having problem in conceiving and holding pregnancy. This test helps to determine if a man is infertile. The analysis will also help determine if sperm dysfunction or sperm count is the reason behind infertility. Majorly, men who had a vasectomy undergo semen analysis to make sure no sperm are in their semen. A movement in a sperm is considered normal if it moves more than 50 per cent an hour after ejaculation.

The IVF industry in India is in boom. The market had witnessed a tremendous growth in the past decade. CASA has helped International Fertility Centre to achieve greater success rate for its patients. Implementation of the CASA technology has increased the success rate of IVF by 51 per cent than the manual screenings. Techniques such as artificial insemination, pre-implantation genetic diagnosis, cryopreservation, CASA help the IVF specialists to skill in the fertility process, according to International Fertility Centre.

(Author is chairperson of International Fertility Centre)


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