How do we get a diagnosis of 21-hydroxylase deficiency primarily?

Dosage of 17-OH-P can be measured in day-3/4 of menses. it can be high (in case of classic type) or moderate (in case of non-classic) We can also perform Synacthene test (ACTH stimulation) to confirm the diagnosis, measure 17-OH-P after 1 hour of administration of ACTH 0.25mg, if higher than 10ng/ml then confirmed.