How to grade a spermatozoon?

11012_16The EQC test will present you several possible answers for the head, midpiece and tail. You can make only one choice. Although you may not be used to grade head shapes in your day-to-day activity, grading head shape is a convenient way of communicating sperm characteristics both to colleagues and medical staff. In our view, it is an important parameter to monitor in an External Quality Control scheme.

Head shapes

Several head shapes and sizes have been described by the WHO (1999, 2010).

Parameters           Morphological aspect
Normal regular oval shape
Macrocephalic the head is clearly above the normal
Microcephalic the head is present but clearly smaller than the normal size
Elongated the head has the form of a cigar
Pyriform the head has the form of a pear
Amorphous the head has slight to strong deviation from oval form
Double two heads attached to one or two midpieces and tails
Pin the head is absent, but the cells is alive and usually moves
Round the head is perfectly spheric and no acrosome is present

Acrosome size

The acrosomal region should be well defined and comprising 40-70% of the head area.


The midpiece should be slender (<1 µm thick) and about 1.5 times the head length. The cytoplasmic droplet should be less than half the width of the head.

Parameters             Morphological aspect
Angulated angulation of the midpiece in respect to the head axis
Asymetrical asymetrical insertion of the midpiece into the head
Thick thick or irregular midpiece
Thin abnormally thin midpiece (absence of mitochondrial sheath)
Cytoplasmic droplet cytoplasmic remnant larger than half of the head’s width


The tail should be straight, uniform, thinner than the midpiece, uncoiled and about 45 µm long. Tail defects are presented below.

Parameters         Morphological aspect
Short or incompletely formed tail Normal tail length is about 40-50 µm.
Multiple A single head may ba associated with multiple tails
Irregular width This parameter may be associated with osmotic effects or staining artifacts
Bent Depending on the smear flagella may be curved, indicating movement of the sperm during the fixation procedure, or remain straight
Coiled Various forms of coiling may occur, either during sperm maturation or after sperm collection (osmotic effects)

Presence of vacuoles

The presence 1-2 vacuoles in the sperm head can be considered as normal. More than 2, should be considered as abnormal, according to the strict criteria.