The best way to test for NCCAH is the 21 Hydroxylase Deficiency With Common Mutationsblood test. This test shows the common genetic mutations associated with NCCAH.
Here is Quest Labs pdf document on the testing procedure. Open pdf, print, take to your doctor/lab. 
Here is a Generic test sheet if your using a different lab. Open pdf, print, take to your doctor/lab.

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Another blood test issued for detection of NCCAH is 17-hydroxyprogesterone. It is also referred to as 17-OHP, Progesterone – 17-OH, or 17-OH Progesterone. In adults, a level greater than 200ng/dL may indicate non-classical adrenal hyperplasia.