Men with a high rate of abnormal sperm are diagnosed with teratozoospermia. There are different criteria to classify the types.
Rate of normal sperm
The number of normal spermatozoa is assessed through a morphological examination. Only those with a perfect shape are taken into account.
All the sperm with a defect (in head, mid-piece or tail) are discarded. After the publication in 2010 by WHO of a guide with the reference values of seminal quality, it was established that normality would be starting from 4%. As the value is very low, it doesn’t make much sense talking about teratospermia according to the quantity of normal sperm. In this way, when we talk about teratospermia, we use the Kruger criteria, stricter than the previous one by taking as minimum reference value 15% of normal sperm.
- Mild teratozoospermia: the number of normal spermatozoa ranges from 14% to 10%.
- Moderate teratozoospermia: between 9% and 5% of spermatozoa are normal.
- Severe teratozoospermia: very few spermatozoa have a good morphology, less than 5%.
Using the sperm sample collected from the patient, a Papanicolau stain is performed in order to observe the spermatozoa and identify what kind of anomaly a spermatozoon has.
The teratozoospermia index is calculated using the following formula:
Teratozoospermia index = ( c + p + q ) / x
- c = head malformations.
p = neck or mid-piece malformations.
q = tail malformations.
x = abnormal amount of spermatozoa.
The index ranges from 1 to 3. 1 refers to anomalies in one area only and 3 is for malformations in the head, neck and tail.
Sperm deformity index
It is calculated through the same formula above, with the only difference that in this index, the total amount of sperm is taken into account. In the previous equation, x refers to the total amount of sperm, regardless their morphology.