The Y-chromosome microdeletion test is used to diagnose the absence of a small chunk of DNA from certain genes on the Y-chromosome which play an important role in spermatogenesis. These microdeletions account for some cases of severe male factor infertility. Depending on the laboratory kit being used different genes on the Y-chromosome can be tested for microdeletions, although the one which is most often tested is the AZF (azoospermia factor) gene. Depending on the specific microdeletion in the AZF gene, the patient may suffer from severe oligoasthenoteratozoospermia or complete azoospermia.