Embryo quality and grading: The good, the bad or the ugly?
Anglia Polytechnic University, East Road, Cambridge, UK, CB1 1PT
04 July 2002
One of the trickiest jobs facing a clinical embryologist is the visual assessment of human embryos. Embryo selection prior to embryo transfer clearly has an enormous impact on the success of the treatment and embryo selection for cryopreservation is equally important to the future success of frozen embryo transfers. Despite the evident importance of this procedure embryo quality is largely guesswork, embryo grading is often inconsistent (even within a given clinic) and there is little or no quality assurance.
There have been some excellent attempts recently to develop non-invasive techniques to assess the quality of human embryos. These include assessment of pronuclear morphology and alignment and the measurement of nutrient uptake by embryos growing in microdrops. Many clinics now utilise the pronuclear morphology technique which is claimed to significantly increase pregnancy rate. I am yet to be convinced about this but it is certainly a step in the right direction. More promising seems to be the nutrient uptake work which at long last can begin to quantify embryo quality. The only problem with the uptake work is at present the procedure requires quite significant analytical expertise making the procedure difficult and expensive to introduce into routine clinical practice. This kind of work is nevertheless essential if we are to move forward in our understanding of embryo quality.
Embryo grading is another cause for concern. First of all there is the inconsistency of the grading scales used. Some clinics use numbers, some use letters and some even ?enhance? their grades with + or - . The result is a confused and often meaningless system with no continuity in the profession. The assessment of the extent of fragmentation is also very erratic with some embryologists over or under-estimating the extent of fragmentation. Some laboratories examine their embryos under high magnification and light intensity, others under the dissecting microscope only. In a scientific procedure, variations such as these will make the overall picture meaningless. A similar situation existed in immunology before the introduction of the CD antigen system, no one really knew which cell was which! It is clearly not practical to attempt to assess surface antigens on human embryos but we should at least attempt to design an international grading scale which means the same thing in each and every laboratory around the World. I would propose either a numerical or percentage scale with no + or ? variables. This will require a lot of hard work and training but if it can be achieved we will at last be able to compare data from different laboratories in a meaningful and scientific way. It is also interesting that many patients focus a lot of attention on the grades of their embryos. If we are going to serve our patients to the best of our abilities it is essential that we have a consistent and meaningful embryo grading system.
Finally it is of some concern that very few laboratories take part in quality assurance (Q.A.) schemes in embryology. Many clinics undertake Q.A. in andrology but very few appear to be involved in any sort of embryological QA. This means that individual embryologists or even complete large clinics may be working inconsistently. There is now an excellent on-line QA website which provides real time QA for each individual embryologist and comparisons with other clinics in the scheme. Such services could dramatically improve the quality of embryology, improve the service we offer to our patients and at last allow clinical embryologists to compare their data in a truly meaningful and scientific way.
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