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.