The EQC test will present you several possible answers for the various characteristics of an oocyte. You can make only one choice. Although you may not be used to grade the oocytes in your day-to-day activity, grading is a convienient way of communicating oocyte characteristics both to colleagues and medical staff. In our view, this is an important parameter to monitor in an External Quality Control scheme.
The zona pellucida (ZP) may vary in thickness and rigidity. Some patients have clearly thiner ZP than others. It is usually a characteristics associated with the patient more than with the oocyte. Although thickness may vary slightly around the oocyte, the following categories can be defined.
|Thin||the ZP is less than 15 µm|
|Thick||the ZP is greater or equal to 25 µm|
|Normal||the ZP is around 20 µm (15-25)|
|Abnormal||the ZP is quite irregular both in thickness and in shape|
The periviteline space surrounds the ooplasm. It is generally clearly visible, at least in the vicinity of the polar bodies. It may contain fragments.
|Small||the ooplasma is adherent to the ZP and the periviteline space is almsot inexistent|
|Large||the the ooplasma is clearly retraced away from the ZP leaving a clearly identifiable space all around the cytoplasm|
|With fragments||presence of clearly identifiable fragments|
|Normal||the ooplasm is slightly retracted away from the ZP at least in the vicinity of the polar body|
The polar body appear when the first meiotic division has been completed. It appears as an small cell close to the oocyte and may undergo a second division. It usually rapidly degenerates and appears as a fragmented structure:
|Unclear or absent||the polar body may not always be clearly identifiable, depending on how the oocyte is oriented. It is absent in a metaphase I oocyte (before the first meiotic division)|
|Intact||clearly identifiable smooth round/oval cell lying close to the oocytes|
|Fragmented||the polar body material is irregular in shape and show clear signs of disorganization|
|Giant||usually intact, giant polar bodies a clearly recognizable, they may achive size of about half of that of an oocyte|
The cytoplasm of the oocyte exhibits usually a granular texture. Depending on the oocyte, this texture may appear homogeneous or exhibit a gradient in the granulated texture. In some cases, it may contain a dark cluster and exhibit sign of fragmentation.
|Fragmented||the cytoplasm shows signs of fragmentation or appear as an undefined mass with absent or degraded oolema|
|Homogeneous||the cytoplasmic material appears homogeneously distributed with little signs of granulation|
|Polarised||zones more or less granulated are visible as two opposing hemispheres|
|Dark cluster||a dark zone is clearly identifiable inside the cytoplasm|
The cytoplasm may contain several remarkable structures.
|Vacuole||one large or several small vacuoles bounded with a clearly identifiable membrane|
|SER cluster||smooth endoplasmic reticulum appearing as clear spherical zones inside the cytoplasm. The boundaries of these structures may not be easily identified as in the case of vacuoles|
|Refractile body||Refractile bodies constitute one of the main morphological abnormalities in human oocytes and are made of auto fluorescing lipofucsin (appear yellowish)|
|None||absence of the above mentioned structures|