For ASD diagnosis in particular, Australia mostly uses DSM-5 rather than ICD-10. Most professionals are now diagnosing just ASD (per DSM-5), rather than the DSM-IV-TR/ICD-10 diagnoses of autism, Aspergers, PDD-NOS, CDD, etc.

Talking about medicine in general, Australia uses ICD-10-AM, which is the Australian national modification of ICD-10. By comparison, the US uses ICD-10-CM, which is the US national modification of ICD-10. Not sure exactly what the differences are – while the ICD-10 and ICD-10-CM code lists are freely available, you have to pay $$$ to even see the ICD-10-AM code list online (or go find a printed copy in a medical school library)