Men with non obstructive infertility have been shown to carry microdeletions of AZF (Azoospermia Factor) sequences in their DNA. Three non overlapping regions have been designated as AZFa, AZFb, and AZFc, and are directly implicated in the spermatogenesis.
(Mol. Hum. Reprod. 4:739-744)

The molecular test for the Y microdeletion is based on a multiplex DNA amplification by polymerase chain reaction (PCR) of the three regions as well as other control regions STS (Sequence Tag Sites) ZFX/ZFY.